Development of Cognition and Language PDF

2022-2023 DEVELOPMENT OF COGNITION AND LANGUAGE PSY4035 Development of Cognition & Language Inhoudsopgave Task 1 – Neural Changes and Methods in Cognitive Development.............................................. 3 How do gray matter and white matter develop over time? What brain regions are associated with this?........................................................................................................................ 3 Which neuroimaging techniques are used to measure development? What are advantages and disadvantages of these techniques?.............................................................. 6 What are methodological issues that need to be dealt with when studying the development of brain functions? How can we try to control these issues?........................... 10 Task 2 – Memory Matters.................................................................................................................. 14 How is working memory different from the other forms of memory? What models for working memory are suggested?................................................................................................. 14 How does working memory develop? What brain regions are involved in working memory? How can you measure it?............................................................................................................. 18 What is the role of working memory problems in learning? How can we improve those problems?........................................................................................................................................ 21 Task 3 – The Dawning of a Personal Past......................................................................................... 26 What is childhood amnesia? How does it relate to memory development?......................... 26 What are theories involved in memory development? What is the complementary process account?......................................................................................................................................... 26 What are the neurobiological explanations for childhood amnesia?..................................... 30 What brain networks/processes underlie the development of episodic memory?............... 32 Task 4 – Words, Words, Words........................................................................................................... 38 What are the steps of word learning? What role does the development of the perceptual system play in the development of word learning?.................................................................. 38 What is the word spurt and what is fast mapping? How are they related?............................ 41 How do you measure fast mapping with ERP?........................................................................... 42 Task 5 – Linking Symbols and Sounds.............................................................................................. 50 How do children learn to read? What goes wrong in dyslexic children?................................ 50 Which brain correlates of visual processing underly normal reading and developmental dyslexia?.......................................................................................................................................... 53 Which brain correlates of phonological processing underly normal reading and developmental dyslexia?.............................................................................................................. 56 Task 6 – Age of Acquisition and Experience in Learning Languages.......................................... 59 How does age influence the neural system underlying language learning?......................... 59 How does experience influence the neural system underlying language learning?............ 61 How do language structure modalities influence development of language networks in the brain?............................................................................................................................................... 65 How are multiple languages represented in the brain?............................................................ 67 Task 7 – How Large is 8?.................................................................................................................... 69 Development of Cognition & Language How does number processing develop?.................................................................................... 69 When/how does number processing become automatized? How can you test this?......... 71 What is the neurological basis of representation of numerical quantities? How can this be tested?............................................................................................................................................. 74 What are the brain areas involved in number processing? What are differences between children and adults?...................................................................................................................... 79 Task 8 – Adding and Adding Makes Two........................................................................................ 80 What kind of processes contribute to arithmetic skills and how do they develop over time?.......................................................................................................................................................... 80 What are the neural correlates/brain networks underlying arithmetic skills? How do they differ between children and adults?........................................................................................... 81 What is dyscalculia? What are the behavioral problems and what are the neural correlates?....................................................................................................................................... 83 What are possible treatments/interventions that could help children with difficulties in arithmetic tasks/dyscalculia?........................................................................................................ 86 Task 9 – The Dynamics of Intelligence and IQ................................................................................ 89 What is IQ? What are the components of IQ? How do you measure IQ?.............................. 89 How do the different aspects of IQ develop?............................................................................ 90 How do early developmental milestones predict later IQ?...................................................... 92 What is the influence of genes and environment on IQ?......................................................... 95 Development of Cognition & Language Task 1 – Neural Changes and Methods in Cognitive Development * How do gray matter and white matter develop over time? What brain regions are associated with this? * Which neuro-imaging techniques are used to measure development? What are advantages and disadvantages of these techniques? * What are methodological issues that need to be dealt with when studying the development of brain functions? How can we try to control these issues? How do gray matter and white matter develop over time? What brain regions are associated with this? Grey matter 1st year: cortical gray matter volumes more than double (108%); subcortical volumes increase sharply o This is region-specific à there is more expansion in the first year in parts of the superior temporal, superior parietal, postcentral, and occipital cortices o Perhaps reflecting rapid development of sensory functions 2nd year: expansion in grey matter (19%) is seen in superior frontal, inferior temporal, and inferior and superior parietal cortices o These are involved in motor planning and higher order visuospatial, sensory, and attentional processing There are decreases in cortical thickness between 3 to 21 years o In contrast, cortical surface area expands up until the age of 12 years o Thus, regional volume increases and decreases are ongoing simultaneously in different parts of the cortex § Increases in temporal and prefrontal cortices in preschool years § Decreases in occipital and primary somatosensory areas in preschool years White matter In white matter there is also faster rate of change during the first than the second year Rapidly increasing fractional anisotropy o Fractional anisotropy = degree of directional restriction of the diffusion of water Rapidly decreasing radial diffusion o Radial diffusion = diffusion in the radial direction (in the direction perpendicular to the long axis) o The more myelinated the connections between neurons are, the lower the radial diffusivity is To a lesser extent there is decrease in axial diffusion o Axial diffusion = diffusion in the direction of the long axis o With axial diffusion you can actually see the tract; radial diffusivity is how myelinated the tract is Region-specific changes o Colossal tracts exhibit larger radial diffusivity changes in the first year § Colossal tracts are the tracts between the two hemispheres o Association tracts continuously show lower maturation degree in the first 2 years of life § Association tracts are the tracts within one hemisphere Development of Cognition & Language o Motor and sensory tracts are more mature at birth and develop more slowly o There is a leftward development of arcuate fasciculus, with more than 20% larger fractional anisotropy values than the right in the first year § This is suggestive of appearing language-related lateralization differences There is maturation from a local to a distributed organization à first isolated regions are formed, but then a synchronized network evolves Increasing white matter integrity is associated with increased fractional anisotropy and decreased radial diffusivity Better working memory scores at 12 months of age relate to higher fractional anisotropy and lower radial diffusivity Figure 1a: larger development first than after Cortical foundations of cognitive development: when less becomes more Cortical reductions in the fronto-parietal network have been related to improvement in working memory and executive function in the age range 5- 10 and 8-22 years But there are also positive correlations found between temporal, frontal, cingulate, precuneus, and early visual area gray matter and intellectual ability in children 6-18 years There is a reversal in a pattern in which more is more (more gray matter is more executive functioning) to more is less (more gray matter is less executive functioning) More is less might be related to pruning, dendritic changes, and myelination processes Development of Cognition & Language Similarly, thinner parietal cortices have been found to predict better verbal learning and memory, visuospatial functioning, and problem solving in the age range 12-14 There is regional variability o Thinner left orbitofrontal cortex predicted better visuospatial recall after 30 minutes (possibly reflecting executive components of memory processes) o Hippocampal volume is positively associated with retention over 1 week (possibly relating to consolidation of memory traces There seems to be parallel development of brain and cognition There is great individual variability within the normal range, wherein differences between healthy and pathological development can typically be of dimensional, rather than of categorical nature Figure 2a: there is a lot of individual variability, so also in typical development there is a lot of variability à so, it is hard to say what volume is the standard volume for a particular age Long-term impact of early brain development Risk groups may show subtle deviances in brain development early on Some early impacts may in principle be observed only decades after o Neonatal brain development and abnormalities have been shown to predict memory, learning and language outcomes, as well as socioemotional development and psychiatric diagnostic status at school age It is plausible that further brain maturation is necessary before the impact of regional alterations on particular symptom domains becomes evident Development of Cognition & Language Effects of early adversities may be continuous, or even become more pronounced with age o But there are also studies showing positive effects of early intervention Influences of early life characteristics on brain and cognition can affect the whole lifespan Genetic and constitutional risk factors interact with postnatal experiential and environmental factors, but it is becoming increasingly clear that influences very early in life are important predictors Which neuroimaging techniques are used to measure development? What are advantages and disadvantages of these techniques? Electroencephalography (EEG) and event-related potentials (ERP) Principles EEG records changes in brain activity over time by measuring the difference in voltage between two electrode sites sampled at regular time intervals Neural activity oscillated at various frequencies linked to different states of alertness à “brain waves” It is measured in cycles per seconds or hertz (Hz) ERPs are averages of epochs of EEG at each electrode site, time-locked in response to specific stimuli o By averaging across several epochs, the activity unrelated to the stimuli averaged out ERPs are characterized by a series of positive- and negative-going waveforms o They are illustrated as changes in (micro)voltage over time The amplitude, latency, and distribution of ERP components provide information about the nature, timing, and organization of the neural systems mediating cognitive processes resulting from specific kinds of stimuli Placement of electrodes: o Can be done with landmarks on the head (nasion on the bridge of the nose and the inion on the bump on the back of the head) o The ideal number of electrodes to use depend on the research question à source localization programs require larger numbers of electrodes than examining one ERP component o An elastic cap can be used, and gel or saline solution is used to facilitate connection between each of the electrodes and the scalp o Time spent placing the electrodes can influence the data recorded à children may perform worse if they get impatient § Completing electrode placement between 10-15 minutes enhances the quality of the EEG EEG recording: o A reference channel is selected that will be subtracted from other active electrode sites during data acquisition o Signals must be amplified to be measured o Noise must be filtered out à can be done during data acquisition but then certain frequencies are permanently eliminated from Development of Cognition & Language the data, so noise can also be filtered out during the analysis of the data ERP signal averaging: o EEG data will be segmented into chunks (epochs) of time that are linked to the presentation of a stimulus o Artefacts need to be identified and corrected or rejected § Movement or other sources of noise o Then activity across time will be averaged per electrode site o In an epoch there needs to be a pre-stimulus interval for a baseline and there needs to be time following the stimulus § Epoch length differs per cognitive process and age § Sensory processes occur earlier than higher cognitive processes § Infants and children have slower brain responses o Trials contaminated with artefacts can be rejected, but it is best to set individual thresholds for rejecting a trial Making sense of ERP components ERP components are named from their polarity and peak latency/order in which they occur o P for positive and N for negative o If there is a negative peak around 400ms it is called P400 o The first positive component can be labeled P1 Latency o Longer latencies are thought to reflect slower processing o Can provide information about the time course of different cognitive events Amplitude o Larger amplitudes are thought to reflect more neural activity o Larger amplitudes are observed in attended than non-attended conditions Distribution across the scalp o The area in which the ERP component is observed or is the largest The polarity, timing, amplitude, and distribution of ERPs elicited by a specific experimental manipulation can change as a function of age It is not known if the infant and adult components are functionally equivalent o It is also not clear if some components evident in infancy have correlates in children and adults Pro’s Inexpensive There are easy-to-use packaged ERP systems available ERPs don’t require an overt response! (behavioral studies typically do) It is well suited to study comprehension independent of production They provide an online measure of cognitive processing They can be used to compare changes in brain activity across the lifespan using the same dependent measure o Habituation, high amplitude sucking, preference for looking, and deferred imitation may be useful only for a limited period of development Very good temporal resolution à milliseconds It is a direct measure of neural activity, which removes a level of inference and interpreting the response to a manipulation Development of Cognition & Language It can reveal information about the brain that can’t be measured by behavior or other cognitive neuroscience techniques ERPs may show qualitative differences in the way the information is processed Cons EEG is sensitive to movement, blinks, and horizontal eye-movement o If there are enough trials per condition, much of the artefact will average out of the data, but if the participant consistently blinks each time they hear a sound, it won’t be averaged out Spatial resolution is quite limited o Electrical activity recorded at a given electrode is a measure of signals produced throughout the brain at that one location, there is some spreading of signal Functional significance of differences in ERP amplitude, latency, and distribution is not simple or transparent and can be subject to misinterpretations Near-Infrared Spectroscopy (NIRS) The biological tissue is relatively transparent to near-infrared light and oxy- and deoxyhemoglobin have differential absorption spectra à this way, hemodynamic responses associated with neural activity can be mapped A typical hemodynamic response to cortical neuronal activation in adults drives an increase in local blood flow that is disproportionate to the local oxygen demand à this leads to an increase in oxy-hemoglobin and a (smaller) decrease in deoxyhemoglobin o = hemodynamic response function (HRF) The light migrates from sources to detectors located on the head by travelling through the skin, skull, and underlying brain tissue o The attenuation of this 650-1000nm wavelength light will be due to absorption and scattering; scattering is assumed to be constant so then the changes in absorption of oxy- and deoxyhemoglobin can be calculated Pro’s Portable Noninvasive à suited for use with infants Inexpensive Better temporal resolution to EEG It doesn’t require participants to be completely motionless o Which makes it better than EEG It has a superior temporal resolution to fMRI It can measure both oxy- and deoxyhemoglobin à more complete measure Cons Temporal resolution is lower than EEG because it measures an HRF, which is slower than electrical response Depth resolution is dependent on the age of the infant and the optical properties of the tissue Development of Cognition & Language Lower spatial resolution compared to MRI (combination of fNIRS and MRI would be good) Magnetic Resonance Imaging (MRI) Basic components of MRI Main magnet to generate a magnetic field, a very strong electrical current is injected into the coil Three magnetic gradient coils à they pulse on and off at different times o They generate gradients in the strength of the magnetic field in the left- right direction, the front-back direction, and the head-toe direction Radiofrequency (RF) transmit coil à sends out brief pulses of RF energy RF receiver coil Basic physics of MRI The nucleus of hydrogen acts like a small magnet with a north and south pole The magnetic dipoles of hydrogen protons are oriented randomly When in the magnetic scanner, a tiny proportion of the hydrogen protons in the tissue will align with the field à forming a very weak magnetization that is aligned with the magnet’s bore (longitudinal magnetization) An RF pulse is then applied at the Larmor frequency, making the spinning protons tip over and precess in unison o Larmor frequency = precession rate à the speed with which the protons precess is completely predictable given the strength of the main magnetic field o This is different for white matter, grey matter, and cerebrospinal fluid (this looks very dark on the image) This in turn generates a small electrical current in the wire coil around the person The speed with which this current decays tells us something about the chemical composition of the tissue surrounding the hydrogen protons Generating MR images Images are acquired slice-by-slice Measurements are decoded by applying a Fourier transformation to the entire set of measurements Varieties of MR images Structural – can be seen as snapshots of the brain at one point in time à quite high resolution Functional – fMRI o Transient changes in the brain occurring over a period of seconds and minutes are measured o Can be used to assess and compare the pattern of functional activation of brain regions in given cognitive tasks o This method is based on blood oxygenation level dependent (BOLD) image contrast § This uses the change in the ratio of oxygenated to deoxygenated hemoglobin in the blood as an indirect measure of changes in the location of neuronal firing § Oxygenated hemoglobin is less paramagnetic than deoxygenated hemoglobin, so when oxygenated blood is more present it increases the overall coherence of the signal in that region Development of Cognition & Language Diffusion Tensor Imaging (DTI) o Measures the directions that water diffuses in brain tissue to reveal the location and orientation of white-matter tracts such as the corpus callosum and the superior longitudinal fasciculus o Water molecules move randomly, and water diffuses differently around white and gray matter § It will move more quickly along white-matter pathways and will not diffuse through them very easily, since they are ensheathed in water-repelling myelin Pro’s Noninvasive à safe magnetic fields o For neonates 4T is safe and for children > 2 months 8T is safe High speed of data acquisition à 4-5 minutes to acquire a single high- resolution scan showing the structure of the whole brain Con’s Need to be careful that there are no metallic objects in the scanner room Scanner can be noisy because of the fast-switching electrical currents It is resource intensive, in terms of cost per hour and the time and experience required to process and analyze MRI data Some children cannot be scanned because of metal in their bodies or because of claustrophobia You must remain still for 5-10 minutes which is difficult for some children There are differences in the extent of head movement between age groups which can introduce confounds Participants must attend for long periods of time à age differences in levels of attention or task compliance are sometimes hard to detect in the scanner but can have considerable impact on patterns of brain activation What are methodological issues that need to be dealt with when studying the development of brain functions? How can we try to control these issues? Schlaggar’s strategy When studying development cross-sectionally, there are difficulties in matching anatomy and performance across age groups To solve these difficulties the following can be done First you have to develop a comparable task base for adults and children o The tasks used by Schlaggar were controlled (effortful) visual lexical (single word) processing task: the participants had to generate a single word verbal response to a visually presented word (reading the word) o This task was used because neural processes underlying these tasks are thought to undergo substantial development between childhood and adulthood o It was an event-related fMRI design with overt verbal response, so both accuracy and RT could be measured Second, a voxel-by-voxel (voxel at baseline compared to a voxel during activation) analysis of variance (ANOVA) on all imaging data in a common stereotactic space (= chosen prototypical brain to compare the activation to) should be done Development of Cognition & Language o Schlaggar chose time as a within-subject factor and age group as a between-subject factor (time because you have a baseline and after a bit of time there will be activation) o There was a main effect of time: suggests that children and adults had similar activity in the left frontal and left extrastriate cortex o However, there was a group x time interaction: so there actually was a difference between adults and children in the left frontal and left extrastriate cortex § Marks the importance of an ANOVA and testing on an interaction effect Third, you have to determine whether the functional anatomical differences found in the interaction effect are due to maturational stage, or due to a poorer (slower and less accurate) performance of the children o If there is overlap in performance, it is possible to create two separate comparison subsets of child and adult data o Matched – child and adult performance (here, RT) is very similar o Nonmatched – there are clear performance differences between adults and children o Comparisons between these subsets can reveal the following § Age/performance-independent region: if the task-related activity in a region were affected by neither age nor performance, it would have similar activity for adults and children in both matched and nonmatched subgroups § Performance-related region: a region where performance has an effect would exhibit minimal if any differences between the matched subgroups, but significant differences between nonmatched subgroups § Age-related region: a region where the activity is affected by the age of the person irrespective of performance, would have dissimilar activity between children and adults in both the matched and nonmatched subgroups o The age/performance-independent regions, by definition, behave similarly ion children and adults o The performance-related regions appear to be affected by time on task and not by age o Findings: § Age/performance-independent à activity in two frontal regions § Performance-related à activity in one left frontal cortex region (more anterior and ventral to the above regions) and in the more posterior left extrastriate cortex region Both greater activation in children in the nonmatched group § Age-related à one left frontal region and one left extrastriate region Left extrastriate age-related region showed more robust activity in children than in adults The frontal region showed significantly greater activation in adults than in children à so children (both overall and in both subgroups) did not have a significant activation in this location Development of Cognition & Language Performance-related regions are an example of how performance mismatch might lead to a false attribution of such differences between age groups to effects of maturation per se à therefore it is important to make these subgroups (matched/nonmatched), so you don’t link differences immediately to maturational differences On the other hand, age-related regions most plausibly reflect effects of brain maturation and indicate that the brain of a child uses, in part, different functional neuroanatomy than that of an adult performing the same task o Explanations for effects of brain maturation: o It could be that the age-related region is immature in children and is incapable of producing sufficient processing to aid in the performance on the task, then the child’s brain adopts an alternative strategy that includes greater use of other brain regions o Alternatively, it could be that because of experience, children have not yet incorporated the processing resources of the region (that adults usually use for that specific task) into a strategy for performing the types of tasks used here, but do so for other tasks Performance is related to experience, age is related to maturation Casey commentary on Schlaggar’s strategy Differences in fMRI results between children and adults are typically reported in terms of the location, magnitude, or volume of brain activity Schlaggar examined brain activity by including time as an independent variable o This way, they could test whether the change in signal peaked at the same time and intensity for the adult and child groups A central question is whether developmental differences in the pattern of brain activity are specific to age or to the accuracy and latency (performance) of the behavior How can one tease apart age differences from behavioral performance differences in brain imaging studies? o By designing tasks a priori that include parametric manipulations in the degree of difficulty, such that children and adults can be compared Development of Cognition & Language on the same or different levels of the task to equate behavioral performance § Different difficulty levels to see if at one point adult and child performance matches § Memory or visual search tasks lend themselves to this design o With sufficient variability and range, you can correlate age and behavioral performance with magnitude or volume activity, showing which brain regions are predominantly related to maturational changes versus behavioral differences. Then each of these variables can be used as a covariate to determine the degree to which these variables independently contribute to changes in brain activity § See if there is a correlation between age and brain activity and see if there is a correlation between performance and brain activity, then you can see which one has the strongest correlation § If performance is also correlated with brain activity, then there is a confound so you have to correct for that, you can analyze this with including the other variable (age if you analyze activity and performance or the other way around) as a covariate § But age and behavioral performance correlate with each other on many behavioral tasks, so this makes this a difficult strategy o Grouping individuals based on their performance post hoc à Schlaggar’s strategy § But this approach is only valuable when the different age groups have overlapping distributions in response latency and accuracy A question that Schlaggar fails to answer is whether the differences in brain activity observed between children and adults are due to an immature central nervous system or a lack of experience with the task (so this is the criticism on Schlaggar) o You can solve this by examining brain activity before and after extended practice on a task to determine whether the immature system after extended practice engages in the same neural mechanisms as the mature system o Highlights the beauty of fMRI because you can repeat the fMRI procedure safely multiple times Development of Cognition & Language Task 2 – Memory Matters * How is working memory different from the other forms of memory? What models for working memory are suggested? * How does working memory develop? What brain regions are involved in working memory? How can you measure it? * What is the role of working memory problems in learning? How can we improve those problems? How is working memory different from the other forms of memory? What models for working memory are suggested? Working memory Is the small amount of information that can be held in mind and used in the execution of cognitive asks Long-term memory = the vast amount of information saved in one’s life WM has often been related to intelligence, information processing, executive function, comprehension, problem solving, and learning in people ranging from infancy to old age, and in all sorts of animals Information in WM can be referring to something as abstract as ideas that can be contemplated or something as concrete as objects that can be counted o It can range from spoken words and printed digits to cars and future meals At first, an incomplete concept might be stored in LTM, leading to misconceptions that are corrected later when discrepancies with further input are noticed, then WM is used to amend the concept in LTM Models of WM John Locke o Distinguished between contemplation, or holding an idea in mind, and memory, or the power to revive an idea after it has disappeared from the mind o Holding in mind is limited to a few concepts at once and reflects what is now called WM o Unlimited store of knowledge from a lifetime is now called LTM William James o Made a distinction between primary memory, the items in consciousness and the trailing edge of what is perceived in the world, and secondary memory, the items in storage but not currently in consciousness George Miller o Discussed the limitation in how many items can be held in immediate memory o Suggested that WM is limited to about 7 chunks, where a chunk is a meaningful unit o In his book, WM was said to be the mental faculty whereby we remember plans and subplans § It is the facility that is used to carry out the subplan while keeping in mind the necessary related subplans and the master plan Atkinson and Shiffrin o Multi-store model of memory Development of Cognition & Language Donald Broadbent o He made an information processing diagram that showed information progressing from a sensory type of store that holds a lot of information briefly à through an attention filter à to essentially a working memory that holds only a few items à to a LTM that is our storehouse of knowledge accumulated through a lifetime o An important theoretical outcome was the discovery of a difference between large-capacity but short-lived sensory memory that was formed regardless of attention, and a longer-lived but small-capacity abstract working memory that required attention Alan Baddeley and Graham Hitch o The term WM was used to indicate a system of temporary memory that is multifaceted, unlike the single store such as James’ primary memory, or the corresponding box in the model by Broadbent o There were diverse effects that appeared to implicate STM, but that did not converge to a single component § Phonological processing interfered most with phonological storage, visual–spatial processing interfered with visual–spatial storage, and a working memory load did not seem to interfere much with superior memory for the end of a list, or recency effect § To account for all these dissociations, they ended up concluding that there was an attention-related control system and various storage systems, these included a phonological system that also included a covert verbal rehearsal process, and a visual-spatial storage system that might have its own type of nonverbal rehearsal o A new component was added in the form of an episodic buffer § This buffer might or might not be attention-dependent and is responsible for holding semantic information short term, as well as the specific binding or association between phonological and visual-spatial information § They called this assembly or system of storage and processing in service of holding information in an accessible form WM à the memory one uses in carrying out cognitive tasks of various kinds o So, there are 3 aspects of WM (visuospatial sketchpad, episodic buffer, phonological loop) § Visuospatial sketchpad is for processing of visual features, location, and trajectory Development of Cognition & Language § Phonological loop is for phonological storage, language, and subvocal rehearsal mechanisms § Episodic buffer is for synthesizing information across modalities § Central executive is for attention, inhibition, switching, resource allocation § Two pieces of information from within one aspect will probably interfere more than two pieces of information from two different aspects of WM Cowan o Broadbent’s model had boxes that were accessed in sequence o Baddeley used a processing diagram in which boxes could be used in parallel o There are 2 aspects of WM storage § The activated portion of LTM § And within that activated portion, a smaller subset of items in the focus of attention § Activated memory would consist of a fragmented soup of all kinds of activated features, whereas the focus of attention would contain just a few well-integrated items or chunks o Instead of separate boxes, he attempted to model on a higher level at which distinctions that were incomplete were not explicitly drawn into the model, and mechanisms could be embedded in other mechanisms § Dissociations could still occur based on similarity of features à two items with phonological features will interfere with one another, e.g., more than one item with phonological features and another item with only visual-spatial features § The model still included central executive processes o Cowan placed more emphasis on sensory memory o The attention filter was also internalized in the model § But instead of information having to pass through the filter, it was assumed that all information activates long-term memory to some degree § The mind forms a neural model of what is processed o The question is whether the activated portion of LTM of Cowan functionally served the same purpose as the phonological and visual- spatial buffers of Baddeley and Hitch § Maybe not, because visual imagery and visual STM seem to be dissociated Ericsson and Kintsch o Long-term WM o They expanded the definition of WM to include relevant information in LTM o It is the use of LTM to serve a function similar to the traditional WM à thus expanding the person’s capabilities o Cowan called it the function virtual short-term memory, meaning a use of long-term memory in a way that STM is usually used Development of Cognition & Language Ongoing controversies about the nature of WM limits There are theoretically 2 ways in which WM could be more limited than LTM First, it could be limited in terms of how many items can be held at once à a capacity limit that Cowan ascribed to the focus of attention Second, it could be limited in the amount of time for which an item remains in the WM when it is no longer rehearsed of refreshed à a decay limit that Cowan ascribed to the activated portion of LTM Both limits are currently controversial The debate is whether the limit occurs in the focus of attention or because materials of similar sorts interfere with one another WM and cognitive development Length of list that can be remembered in digit span increases steadily with childhood maturation, until late childhood Explanations based on capacity o Developmental increases are attributed to increases in the number of items that could be held in mind at once o Knowledge allows some problems to be solved with less WM requirement Explanations based on knowledge o Knowledge increases with age o The familiarity with the materials determines the processing speed, which in turn determines the span Explanations based on processing speed and strategies o Speed of processing increases with age in childhood and decreases again with old age o Working memory improvement could also be based on an increased rate of verbal rehearsal or increased rate of attention refreshing § Young children don’t rehearse at all, or do not rehearse in a sufficiently sophisticated manner that is needed to assist in recall Reassessment of capacity accounts There are reasons to care about whether the growth of capacity is primary, or whether it is derived from some other type of development If growth of capacity results only from growth of knowledge, then it should be possible to teach any concept at any age, if the concept can be made familiar enough o However, the author suggests that knowledge differences cannot account for the age difference in WM capacity If capacity differences come from speed differences, it might be possible to allow more time by making sure that the parts to be incorporated into a new concept are presented sufficiently slowly Other things that cannot account for age difference in capacity o The inability to filter out irrelevant information o Encoding speed o Rehearsal Therefore, it is suggested that age differences in capacity may be primary rather than derived from another process Several aspects of WM are likely to develop à capacity, speed, knowledge, and the use of strategies Development of Cognition & Language o Although it is not always easy to know which process is primary, these aspects of development all should contribute in some way to our policies regarding learning and education Tests of WM In an experimental setting, an individual’s WM capacity is reliably assessed by tasks in which the individual is required to process and store increasing amounts of information until the point at which recall errors are made o Such as the reading span à participants make judgments about the semantic properties of sentences while remembering the last word of each sentence in sequence Tasks of short-term memory, in contrast, place menial demands on processing and are often described as storage-only tasks o Verbal STM is traditionally assessed using tasks that require the participant to recall a sequence of verbal information, such as digit span and word span o It usually involves retention of either spatial or visual information How does working memory develop? What brain regions are involved in working memory? How can you measure it? Study by Tamnes Is working memory development related to changes in cortical and subcortical volumes during childhood and adolescence? Do these relationships interact with age? They hypothesized that improvement in WM performance would be associated with volume reduction in the network of prefrontal and posterior parietal cortices supporting WM functions as well as in BG structures They also hypothesized that the relationships would vary with age and be stronger in children than in adolescents Methods Children and adolescents aged 8-19 years were tested at 2 timepoints They had to do the keep track task o There were 6 categories: animals, clothing, colors, countries, fruit, and relatives o Participants were first shown several target categories on the lower half of the computer screen, and exemplars from each of the six possible categories o The target categories remained on the screen during the trial o The task was to recall the last word presented in each of the target categories (so you must update if there is a new exemplar presented of your target category, and you can ignore exemplars that are not in your target category) o Immediately after each trial, participants were asked to recall these words, and the task administrator wrote down their response and encouraged the participants to guess if an insufficient number of words were recalled The percentage of words recalled correctly was recorded at both time points Change in WM performance (score at T2 – score at T1) and annual change (change/scan interval) was then calculated Development of Cognition & Language Intelligence level was estimated at both time points by the Wechsler Abbreviated Scale of Intelligence Results Mean annual change in WM performance was significant o Was negatively correlated with age o The degree of improvement in WM decreased linearly over the investigated age range Annual change in WM performance was significant in childhood and early adolescence, but not in late adolescence Annual change in WM performance was not related to change in intellectual abilities or to intelligence level at T1 The degree of improvement in WM performance was related to the degree of cortical volume reduction o Effects found bilaterally in prefrontal clusters à superior frontal and rostral middle frontal gyri and the frontal poles o Effects found in clusters around the central sulci extending into caudal middle frontal gyrus in left hemisphere and into supramarginal and superior temporal gyri in the right hemisphere o Bilateral clusters were observed encompassing substantial parts of the superior and inferior parietal cortices and in the right hemisphere additionally extending down into the lateral occipital regions When a hierarchical multiple regression on annual change in WM performance was done à only the parietal right hemisphere cluster had a unique prediction value (predicted annual change in WM performance) Development of Cognition & Language The relationships between WM improvement and cortical volume reductions were not explained by differences in either intelligence level or change in intellectual abilities There were no significant relationships between change in WM performance and change in any of the subcortical structures There was no significant interaction between WM change and age Blue areas in figure 3 indicate reductions in cortical volume à pruning Discussion Associations between WM development and cortical and subcortical structural maturation in children and adolescents were examined 3 main findings o The degree of improvement in verbal WM performance decreased linearly over the investigated age range (8-22 years) o WM development was related to cortical volume reduction in widespread frontal and parietal regions, overlapping a fronto-parietal network active in WM tasks o These relationships did not significantly interact with age Results revealed 3 cortical regions in each hemisphere where the extent of improvement in verbal WM performance was related to the degree of volume decrease o The largest effects were seen in bilateral prefrontal and posterior parietal regions, and additional effects were found in regions around the central sulci Development of Cognition & Language o Thus, a fronto-parietal network supports WM function and structural maturation of these cortical regions is related to the development of WM Lecture WM capacity develops until at least early adulthood Different WM systems have a unique developmental pattern From left to right: development of phonological loop, development of central executive, development of visuospatial sketchpad What is the role of working memory problems in learning? How can we improve those problems? WM and learning There are several ways in which WM can influence learning It is important to have sufficient WM for concept information, and the control processes and mnemonic strategies used with WM are also critical to learning Concept formation o Learning might be thought of in an educational context as the formation of new concepts o These new concepts occur when existing concepts are joined or bound together o According to Cowan’s view, the binding of ideas occurs more specifically in the focus of attention o Theory of Halford suggests why a good WM is important for learning § More complex concepts require that one consider the relationship between more parts § A person’s working memory can be insufficient for a complex concept § It may be possible to memorize that concept with less working memory, but not truly to understand the concept and work with it Control processes o One of the most important aspects of learning is staying on task o If one doesn’t stick to the relevant goals, one will learn something perhaps, but it will not be the desired learning o The individuals who are more affected by the Stroop condition are those with relatively low performance on the operation span test of working memory (carrying out arithmetic problems while remembering words interleaved with those problems) Development of Cognition & Language o WM failures appear to be a large part of learning disabilities Mnemonic strategies o A sophisticated rehearsal strategy for free recall of a list involves a rehearsal method that is cumulative (1, 12, 123, 1234) o For long-term learning, maintenance rehearsal is not as effective as elaborative rehearsal à a coherent story is made based on the items § This takes time but results in richer associations between items, enhancing LTM if there is time for it to be accomplished o Chunking à the formation of new associations or recognition of existing ones to reduce the number of independent items to keep track of in working memory § Is a more general mnemonic strategy o The importance of a good WM comes in when something new is learned, and logical connections are not yet formed so the WM loas is high § WM is taxed until the material can be logically organized into a coherent structure WM and education Teaching to the level of WM o We should try to adjust the materials to fit the learner § A heavy dose of personal monitoring and adjustment is needed to make sure that the task is sufficiently motivating for every student o Cognitive load theory (by Sweller) à distinguishes between an intrinsic cognitive load that comes from the material to be learned and an extraneous cognitive load that should be kept small enough that the cognitive resources of the learner are not overly depleted by it o With too high a cognitive load, one runs the risk of the student not being able to follow the presentation, whereas with too low a cognitive load, one runs the risk of insufficient engagement WM training o Doing WM training studies is not easy § One needs a control group that is just as motivated by the task as the training group but without the WM training aspect § The training task must be adaptive (with rewards for performance that continues to improve with training) and a non- adaptive control group does not adequately control arousal and motivation § Some task that is adaptive but involves long-term learning instead of WM training may be adequate o WM training sometimes improves performance on the WM task that is trained, but doesn’t generalize to reasoning tasks that must rely on WM o In contrast, other reviews suggest that the training of executive functions (inhibiting irrelevant information, updating WM, controlling attention, etc.) does extend at least to tasks that use similar processes and some basically concur also for WM o Ways in which training can improve task performance § WM training theoretically might increase the function of a basic process, much as a muscle can be strengthened through practice Development of Cognition & Language § It is possible for WM training to result in the discovery of a strategy for completing the task that is better than the strategy used initially How does working memory work in the classroom? A minor distraction such as an unrelated thought springing to mind or an interruption by someone else is likely to result in complete loss of the stored information, and so in a failed attempt to do a WM task There is a steady developmental improvement in WM performance between 4 and 11 years à linear increase continues to about 12 years, with performance levelling off towards 15 years There is a substantial degree of variability at each age o Individual differences in the capacity of WM have important consequences for children’s ability to acquire knowledge and new skills Working memory and reading o Children with reading disabilities show significant and marked decrements on verbal WM tasks relative to typically developing individuals o In typically developing children, scores on WM tasks predict reading achievement independently of measures of verbal STM and phonological awareness skills o This dissociation in performance between children with reading disabilities and typically developing children is explained as the result of limited capacity for simultaneous processing and storage of information characteristic of WM tasks, rather than a processing deficiency or specific problem with verbal short-term reading in poor readers o WM skills of children with reading disabilities don’t improve over time à it is a sustained deficit, rather than a developmental lag Working memory and mathematics o Associations between WM and mathematical skills vary as a function of sample age as well as mathematical tasks o The relationship between memory and math in 7-year-olds is significant, but not anymore in adolescents § It is possible that verbal WM plays a crucial role in mathematical performance when children are younger, however as they get older, other factors such as number knowledge and strategies play a greater role o Mathematical deficits could result from poor WM abilities § Low WM scores are closely related to computational skills § Weal verbal WM skills are also characteristic of poor performance on arithmetic word problems § Common failures include impaired recall on both word and number-based WM stimuli and increased intrusion errors o Mathematical abilities don’t improve substantially during schooling, suggesting that such deficits are persistent and cannot be made up over time o Visuo-spatial memory functions as a mental blackboard, supporting number representation, such as place value and alignment in columns, in counting and arithmetic Development of Cognition & Language § Children with poor visuo-spatial memory skills have less room in their blackboard to keep in mind the relevant numerical information Working memory and general learning deficits o Children with special educational needs had WM deficits that varied in severity o Children with general learning difficulties that included both literacy and mathematics performed poorly in all areas of WM, whereas children with problems of a behavioral or emotional nature performed normally on all the memory assessments Working memory in the classroom o Children with poor verbal working memory but normal nonverbal IQ in their first year of formal schooling struggle with tasks involving simultaneous storage and processing of information o Common failures for children with WM impairments § Forgetting lengthy instructions § Failure to cope with simultaneous processing and storage demands o Explanation for these failures à storage and processing demands of the activities are beyond the WM capacity of these children § The added processing demands increase the WM demands and so lead to memory failure o Why does WM constrain learning? § One suggestion is that WM provides a resource for the individual to integrate knowledge from LTM with information in temporary storage à a child with weak WM capacities is therefore limited in their ability to perform this operation in important classroom- based activities § Another suggestion is that poor WM skills result in pervasive learning difficulties because this system acts as a bottleneck for learning in many of the individual learning episodes required to increment the acquisition of knowledge à because low WM children often fail to meet WM demands of individual learning episodes, the incremental process of acquiring skill and knowledge over the school years is disrupted Practical applications: What can be done to ameliorate the learning difficulties resulting from impairments of WM? o There is little evidence that training WM in children with low WM skills leads to substantial gains in academic attainments o However, learning progress of children with poor WM skills can be improved dramatically by reducing WM demands in the classroom o First, it is important to ensure that the child can remember what they are doing § Keeping the instructions as brief and simple as possible § Frequent repetition of the instructions § Ask the child to repeat it o Second, in activities that involve the child in processing and storage information, WM demands and hence task failures will be reduced if the processing demands are decreased § Sentence processing difficulty can be lessened by reducing the linguistic complexity of the sentence Development of Cognition & Language § Simplifying the vocabulary and using common rather than more unusual words § Syntax of the sentence can be simplified à use simple structures such as active subject-verb-object constructions rather than sentences with a complex causal structure o Third, the problem of the child losing their place in a complex activity can be reduced by breaking down the tasks into separate steps, and by providing memory support § External memory aids such as useful spellings displayed on the teacher’s board or the classroom walls and number lines § However, children with poor WM function often don’t use these memory aids Therefore, encourage children’s use of memory aids à give the child regular periods of practice in the use of the aids in the context of simple activities with few WM demands o Finally, help children develop effective strategies for coping with situations in which they experience WM failures § Encourage the child to ask for forgotten information where necessary, train the use of memory aids, encourage the child to continue with complex tasks rather than abandoning them even if some of the steps are not completed due to memory failure Development of Cognition & Language Task 3 – The Dawning of a Personal Past * What is childhood amnesia? How does it relate to memory development? * What are theories involved in memory development? What is the complementary process account? * What are the neurobiological explanations for childhood amnesia? * What brain networks/processes underlie the development of episodic memory? What is childhood amnesia? How does it relate to memory development? Childhood amnesia First phase: 2-3 years à absence of memory o Adults generally cannot remember events that occurred in the first 2-3 years of life The second phase: 3-7 years à spotty memory o Adults recall very few memories from ages 3-7 years The number of memories that adults are able to retrieve increases gradually à after age 7, a steeper, more adult-like distribution becomes apparent, and the rate of forgetting is assumed to be adult-like There are individual differences among adults in the density of early memories, some adults recall many memories from their childhood, whereas others remember only a few with many months between them Childhood amnesia cannot be attributed to normal forgetting with the passage of time, simply because those memories are from the longest ago Children can form and verbally report event memories, so it is not the incapability of forming memories that accounts for childhood amnesia Older children remember longer o Although young children can acquire memories, they forget faster than older children o This faster forgetting is independent of the task used to measure memory and is argues to be independent of differences in memory encoding What are theories involved in memory development? What is the complementary process account? Human cognitive/psychological theories Emphasize that the ability to form enduring memories (the offset of childhood amnesia) in humans coincides with emergence of developmental milestones, such as the acquisition of the sense of self, theory of mind, or language But childhood amnesia is also observed in non-human species, so it is unlikely that this phenomenon can be explained fully using purely human concepts Information processing theories Postulate that childhood amnesia results from impaired memory encoding, storage, and/or retrieval o However, there is evidence that doesn’t support this Development of Cognition & Language Other explanations of childhood amnesia focus on memory retrieval and postulate that the memories formed in childhood are permanently stored and always exist, but that these memories simply cannot be accessed during adulthood o = retrieval deficit hypothesis Biological theories The immature brain: childhood amnesia occurs because key structures for memory formation and storage are insufficiently mature at the time of memory formation to process these memories o Support comes from findings that, while much of the brain is fully formed at birth, the two key regions for declarative memory (cortex and hippocampus) show protracted postnatal development § Especially the dentate gyrus region of the hippocampus § This suggests that the prolonged hippocampal development can account for childhood amnesia Ongoing brain maturation: the process of ongoing maturation interferes with stable memory consolidation o While memory formation is more of less normal in infants, continued brain maturation after initial acquisition may interfere with stabilization or consolidation of the memory trace o Josselyn et al. propose that one specific aspect of brain maturation, neurogenesis, regulates the ability to form enduring hippocampus- dependent memories § See first learning goal Complementary process account of childhood amnesia (Bauer) There are theories that posit late development of the capacity to create personal memories, but these theories don’t take into account the possibility that memories of early life events were formed but then were lost to recollection o In this case, childhood amnesia is failure to form memories in the first place There are theories that posit events that cause the later functional disappearance of early memories, but these theories don’t take into account the possibility that the memories that subsequently disappeared may have been especially vulnerable to forgetting because of poor quality of the traces themselves Thus, theories emphasize either positive changes in memory (emergence of a new memory system), or negative changes (loss of accessibility) o Theories about positive changes in memory à autobiographical memory is a developmentally later achievement, one that emerges only with either general or specific cognitive developmental changes o Theories about negative changes in memory à autobiographical memories are formed, even early in life, but the rate of forgetting is accelerated in childhood The complementary process account states that there are two complementary processes that improve memory traces and that degrade them Development of Cognition & Language o On the one hand there are developmental changes in a number of factors and processes that facilitate encoding, consolidation, and later retrieval of memory traces, eventually leading to a corpus of personal memories o On the other hand, there are a number of factors and processes that undermine the integrity of memory traces, eventually rendering some inaccessible to later recollection o Neither set of processes alone is sufficient to account for childhood amnesia o It highlights the developments that result in formation of memory traces that bear more, better elaborated, and more tightly integrated autobiographical features o It also highlights developmental changes in the rate of forgetting associated with normative neural, cognitive, and mnemonic processes that result in decreases in the vulnerability of memory traces Processes that improve memory traces o Memory traces are increasingly autobiographical with development o There are elements of autobiographical memory in the behavior of infants, even before the end of the second life o The number and variety of elements increases over early childhood (and beyond) and the elements become better elaborated and more tightly integrated with one another o As a result, it becomes easier and easier to “see” autobiographical memory Processes that degrade memory traces o The paradox of childhood amnesia: if memory gets better and more autobiographical, why is it that so few memories from the first years of life survive? § Because memories are vulnerable, especially those formed in early life § Children forget at a faster rate, relative to adults § Early memories are forgotten because of normative processes involved in transformation of labile representations of experience into enduring memory traces o Childhood amnesia emerges by middle childhood § Specifically, by 8 to 9 years of age, children have forgotten a substantial proportion of early childhood events they once remembered § As a consequence of exponential forgetting by children is that the pool of autobiographical memories they have formed eventually diminishes to isolated puddles of memories Development of Cognition & Language § Isolation makes the remaining memories even more difficult to retrieve Processes involved in the formation of memory traces o Memory begins with encoding of experience into a memory trace § Stimuli are experienced and processed by primary sensory areas Primary somatosensory cortex à object or event-related tactile information Primary visual cortex à form, color, and motion of the object or event Primary auditory cortex à sounds associated with the object or event § From there they are sent to unimodal association areas Here the inputs are integrated into whole percepts of what the object or event feels like, looks like, and sounds like § From there the information is sent to polymodal/multimodal association areas Posterior-parietal, anterior-prefrontal, and limbic-temporal This activity gives rise to experience of a coherent event o For the experience of an event to endure as a memory, the information must be consolidated § This happens through projections from the cortical association areas to the medial temporal lobes § MTL projects non-spatial/object info to perirhinal cortex § MTL projects spatial/contextual info to parahippocampal cortex § This information is held here in medial temporal cortices as a temporarily à temporary storage o To be stabilized into a coherent memory trace, information must make its way into the hippocampus proper § First information is sent from temporary storage to the entorhinal cortex § Specifically, perirhinal cortex sends to the lateral aspect of the entorhinal cortex, parahippocampal cortex sends to the medial aspects of the entorhinal cortex § From there, projections are sent to the hippocampus, where all of the different components of the event are bound into a single representation Why is childhood a period of accelerated forgetting? o There is a binding of elements of experience in the hippocampus, which depends upon iterative processing of the conjunctions and relations among the stimuli that gave rise to the event à the pattern is regularly refreshed by additional neural signaling among the hippocampus, the surrounding medial temporal cortices, and the association areas o The hippocampus also maintains and strengthens linkages between the distributed cortical representations that make up the entire event, and eventually the representations no longer require the activity of the hippocampus for their maintenance § Memory traces do remain dependent on the hippocampus for retrieval Development of Cognition & Language o In the first several months of life, the substrate responsible for forming memory traces develops rapidly à as infants approach the end of the second year, the neural structures and network connections seemingly have reached a level of maturity sufficient to support their signatory function § But it is far from fully mature o Later, the structures and network continue to develop, leading to increases in the efficiency and thus the efficacy with which it glues or binds together the elements of experience into enduring traces § The rate of progress is relatively slow, such that at least for the first decade of life, effective loss from memory is faster than the rate in adolescence and adulthood Summary o For the first 2 years of life, encoding, consolidation, and subsequent retrieval of long-term memories of specific past events are fragile processes owing to immaturity of the neural substrate that supports these signatory functions o For years thereafter, the substrate operates relatively inefficiently and ineffectively § Result: the elements of experience that are the raw materials for memory are not effectively stabilized or integrated into long- term memory stores o Together, these forces create a dynamic à memories of the first years of life are formed and may survive over some period of time, but they are challenged to survive for the long term o Over developmental time, individual memory representations include more and more of the features that characterize autobiographical memories and the features themselves are better elaborated and more tightly integrated with one another § Result: higher quality mnemonic materials o At the same time, there are developments in the neural substrate operating on the available representations § Structural development and development of connectivity of the network of structures § These developments result in more efficient and effective cognitive and mnemonic processing, which results in decreases in the vulnerability of memory traces, and thus in the rate of forgetting § Net effect: more and more memories of higher quality survive to be recalled at later points of time, producing the characteristic distribution of autobiographical memories across the life span What are the neurobiological explanations for childhood amnesia? Neurogenic hypothesis of childhood amnesia New neurons continue to be added to the hippocampus, a brain region important for memory Development of Cognition & Language The levels of neurogenesis and memory stability are inversely related: the inability to form stable, persistent memories in early life coincides with a period of high neurogenesis, whereas the ability to form stable, persistent memories only emerges at later developmental periods as the rate of neurogenesis declines Neurogenic hypothesis of childhood amnesia: the integration of new neurons degrades existing memories by either increasing the excitability (and therefore instability) of hippocampal memory networks, or replacing the synaptic connections in preexisting hippocampal circuits o Data suggest that postnatal neurogenesis could have a substantial impact on hippocampal circuit function in rodents and primates, including humans There may be at least two ways in which adding new neurons might degrade existing memories o First, the integration of new neurons necessarily alters the wiring of existing hippocampal networks § As memory fidelity likely depends on the precise spatiotemporal activation of hippocampal neurons, any changes in network architecture would likely result in information loss § The invasion of new neurons into a preexisting circuit may disrupt the integrity of previously formed synapses, leading to the loss of stored information o Second, immature granule neurons are more excitable than mature granule neurons § The addition of new excitable neurons into hippocampal circuits would result in an increase in overall excitatory drive, both within the DG and in downstream CA3 networks § To avoid maladaptive consequences of overexcitation, homeostatic mechanisms that regulate neuronal and/or circuit excitability may be invoked § Such homeostatic changes may include decreasing the intrinsic excitability of DG/CA3 neurons or neuron-wide synaptic rescaling This may eventually lead to the silencing of some synapses, thus compromising information storage There are some studies that provide support for the idea that integration of new granule cells into hippocampal circuitry may promote the degradation and/or clearance of existing information from the hippocampus Development of Cognition & Language What brain networks/processes underlie the development of episodic memory? Explicit memory is defined as the memory for facts about the world (semantic memory) and autobiographical events (episodic memory) o It depends on middle temporal lobe (MTL) structures Implicit memory includes habits, skills, priming, classical conditioning, and non- associative learning o Is subserved by a variety of brain regions such as the striatum, cerebellum, or regions of the neocortex Hippocampus The hippocampal formation receives highly processed and integrated information from unimodal and polymodal regions of the neocortex via the entorhinal cortex It further integrates and processes this rich set of information before sending even more highly integrated, complex information back to most of the regions of origin, where long-term memory is thought to be consolidated It is proposed that the hippocampus is involved in the binding of information from the neocortex o However, this model considers the hippocampal formation as a single entity and does not define the specific role of distinct hippocampal regions in memory processing The hippocampus is composed of distinct regions interconnected both serially and in parallel o Neocortical information reaches the hippocampal formation mainly via the entorhinal cortex and is sent through the main hippocampal regions § First the dentate gyrus, then CA3, CA1, and finally the subiculum o Then it is sent back to the entorhinal cortex, closing a functional loop for information processing within the hippocampal formation o These hippocampal regions (CA3, CA2, CA1, subiculum) might receive and process information independently from the region located upstream in the hippocampal loop for information Functions that depend on the hippocampal formation o Recognition memory § Visual recognition memory is the earliest-emerging memory function § Can be tested with visual paired-comparison (VPC) tasks § Is functional shortly after birth § At least part of the hippocampal formation circuitry is relatively mature at birth and might subserve the early emergence of recognition memory around birth o Basic relational memory functions (CA1) Development of Cognition & Language § = relations between different objects on a picture or the temporal relations between actions § Emerge later than recognition memory à 9 months of age/between 6 and 12 months of age § Spatial relational memory emerges around 21 months (children are then able to locate a hidden toy in a sandbox when distant environmental cues are available) § It is argued that development of CA1 corresponds to this Argued that CA1 is involved in relational memory, is necessary for the memory of sequences of events that compose unique episodes, and is implicated in spatial memory, as CA1 “place-cells” have been reported to fire according to a rat’s location in the environment o Complex relational memory functions (CA3) § The ability to establish nonspatial relational memory representations might be rudimentary, and it becomes more elaborate with age during the first 2 years § Infants might learn the relation between items and their context, but this relational representation is unitary at first à relational memory is at first extremely specific to the context in which learning occurs and gradually becomes more and more “flexible” § This flexibility is a fundamental component of relational memory § CA1 might subserve the integration of its inputs into a unitary representation (less flexible), whereas CA3, and its large association network, stores the different parts of a representation separately Development of CA3 (and dentate gyrus) à more flexible, context-independent relational memory Dentate gyrus has been found to subserve pattern separation (so that it is not context dependent) § It has been proposed that CA3 is an auto-association network that facilitates the retrieval of a whole representation by activation of only a small part of this representation § CA3 representations are stored in an unstructured manner à a large number of memories can be stored and interference between memories is kept as low as possible due to the sparseness of its connections o Episodic memory (dentate gyrus) § Memory for events that occur in a unique spatiotemporal context § Is the latest-emerging hippocampal-dependent memory function § Age-related qualitative changes in the kind of information encoded and how it is encoded might lead to the decline of childhood amnesia around preschool age § Maturation of the dentate gyrus and its projections to CA3 constitute the formation of episodic memories § Dentate gyrus is involved in the formation of temporal associations between events Development of Cognition & Language § Temporal coding of events might first be subserved by CA1, which allows the encoding and remembering of a sequence of events happening over a short period of time (minutes) Later, maturation of the dentate gyrus subserves the ability to create distinct memories of personal life episodes happening over a longer but restricted period of time (several hours or a day) Changes in the memory system across the lifespan Predictive interactive multiple memory system (PIMMS) framework proposes 3 memory systems o From highest to lowest memory system: episodic, semantic, perceptual § Episodic: hippocampus Records events defined by a feature at a given context (i.e., background where the feature occurred) or co- occurrence of two or more unrelated features § Semantic: perirhinal cortex Records combinations of perceptually defined features that repeatedly co-occur in the environment à familiarity-based retrieval mechanism § Perceptual: occipitotemporal cortex Extracts and represents features of incoming information o It highlights the predictive interactions between these systems as the general principle of operation between and within them § Long-term memory has a predicting function o Feedback from higher memory systems predict activity in lower systems (e.g., entering a bathroom may predict items that are likely to occur in that context) Development of Cognition & Language o Feed-forward flow of information, on the other hand, transmits the difference between such top-down predictions and the current bottom-up input o This way, prediction error is computed, and this serves as a general process enabling the operation of memory systems and interaction between systems PIMMS assumes that there are interactions between the hippocampus, perirhinal cortex, and the ventral visual system for the purpose of predictive memory for item categories (= higher conceptual abstract knowledge) o This is achieved through dynamic interactions between the hippocampus and neocortex, including the medial prefrontal cortex o The hippocampus allows the integration, separation, and comparison of information from distributed brain regions o The medial PFC integrates higher level (abstract) semantic knowledge § Integrates abstract representations across modalities with behavioral output and represents semantic knowledge § With this, it is assumed that episodic memory gives rise to abstract knowledge that is akin to semantic memory o Lateral PFC (DLPFC, VLPFC, anterior PFC) is for goal-directed control functions that support the encoding of discrete memory traces, and the subsequent strategic retrieval and evaluation of stored representations o There are interactions between medial temporal lobe and mPFC, such that mPFC detects the congruency of new information with existing information in neocortex During development of memory systems, there is a shift from reliance on concrete representations to reliance on abstract knowledge o Because semantic knowledge may be less developed during childhood o Perceptual development may also contribute to improvement in semantic representations Through development, the semantic and episodic systems become increasingly segregated and become progressively independent of one another o Distinct systems in adults may be less differentiated in children o Especially semantic and episodic memory systems gradually differentiate over development Higher-level abstract knowledge and top-down control by frontal regions guide memory functions and lead to a better differentiation among the three systems over development Childhood and adolescence are periods of robust change in the structure and function of the brain o Memory for high-level visual stimuli such as natural scenes and faces grows from childhood through adolescence into young adulthood o Posterior parahippocampal gyrus (parahippocampal place area) grows in size from childhood through adulthood, and this correlates with improved recognition memory for scenes o This supports the notion that developmental trends in perception influence episodic memory The hierarchy and information flow between the systems is different in children and adults Development of Cognition & Language o Perceptual information takes front stage to semantic categorization in children o During childhood, episodic encoding may depend more on perceptual systems, whereas established representations of semantic knowledge as well as top-down frontal control systems become more prominent in the encoding process in adulthood In adults, episodic memory is supported by the hippocampus, which is needed in detailed representations, and in supporting recollection of the past o In children, the hippocampus may be involved in the encoding and retrieval of new information, including non-recollection based memory that, in adults, is relatively less dependent on the hippocampus Verbal and visual episodic memory declines in old age, around 60-65 years o Knowledge and skills learned long ago persist, in at least partially accessible form, for long periods of time § Permastore = the idea that once information is entered in semantic memory, it stays there, with the only issue being the extent to which it could be accessed o But decline in control processes may produce impairments in direct access to this knowledge o In line with a decline in control over memory, older adults show impairment in flexibility to switch between recalling fine-grained detail and gist information § Optimal remembering requires the flexible disposal of detailed recollection and recall of abstract or gist-based information o The aging memory system shows weakened processing of new information and over-reliance on previously stored patterns o There is a strong pull toward settling into a stable state driven by prediction generated from the semantic system, which leads to a reduced capacity for generating new individual representations rich in unique details (weakening in contribution of the episodic and perceptual systems) o In old age, MTL gray and white matter exhibit profound decline § Changes are especially pronounced in the hippocampus, less so in the surrounding cortex § Aging-related volume reductions are found in CA1, DG/CA3 and subiculum Development of Cognition & Language Example going from episodic to semantic memory with the help of me

Development of Cognition and Language PDF

Document Details

Tags

Related

Summary

Full Transcript

Upgrade to continue