Psychology Exam Notes PDF

**Learning, Memory and Amnesia** **What is Memory?** - **Memory** is the ability to store and retrieve information over time. It is fundamental to our sense of self and our ability to interact with the world. **Studying Memory** - The study of **learning** is key to understanding **m...

**Learning, Memory and Amnesia** **What is Memory?** - **Memory** is the ability to store and retrieve information over time. It is fundamental to our sense of self and our ability to interact with the world. **Studying Memory** - The study of **learning** is key to understanding **memory**, as learning causes physical changes in the brain that produce memory. - To study the **physiology of learning and memory**, researchers must characterise how learning occurs. - Psychologists traditionally distinguish two major categories of learning: **classical conditioning** and **instrumental conditioning**. - Some learning is hard to label as classical or instrumental, and animals also have specialized learning methods. **Localised Representations of Memory** - **Engram** refers to the physical representation of what has been learned. - **Karl Lashley** attempted to find the **engram**. - He trained rats on mazes and a brightness discrimination task, and then made cuts in their cerebral cortices. However, no knife cut significantly impaired the rats\' performance. - He also trained rats on mazes before or after removing large parts of the cortex. This impaired performance, but the deficit depended more on the amount of damage than on its location. - He concluded that learning and memory did not rely on a single cortical area. - Lashley proposed two principles about the nervous system: **equipotentiality** (all parts of the cortex contribute equally to complex behaviours such as learning) and **mass action** (the cortex works as a whole, and more cortex is better). - Researchers concluded that Lashley\'s conclusions were based on the incorrect assumptions that the cerebral cortex was the best or only place to find an engram and that all types of learning were the same. **Richard F. Thompson\'s Research** - **Richard F. Thompson** attempted to find an **engram** for memory in the cerebellum. - Thompson and colleagues studied **classical conditioning** of eyelid responses in rabbits. - Rabbits were presented with a tone (conditioned stimulus) followed by a puff of air to the cornea (unconditioned stimulus). This caused the rabbit to blink (unconditioned response). - After repeated pairings of the stimuli, the rabbits blinked at the tone (conditioned response). - Researchers recorded the activity in various brain cells to see which ones changed during learning. - They found that the **lateral interpositus nucleus (LIP)** of the cerebellum was essential for learning. - At the start of training, the cells in the LIP showed little response to the tone, but their responses increased as learning progressed. - Suppressing the LIP during training resulted in no response to the stimuli, and the rabbits learned at the same speed as those that had received no training. - Thompson\'s research also found that the **red nucleus** is necessary for performing a conditioned response, but not for learning the response. - The red nucleus is a midbrain motor area that receives input from the cerebellum. - Suppressing the red nucleus temporarily prevented responses during training, but the rabbits learned the response. - Thompson concluded that learning occurred in the **LIP**. - The mechanisms for this type of conditioning are likely similar in humans. - PET scans have shown that conditioned eyeblinks in young adults cause increased activity in the cerebellum, red nucleus and other areas. - People with damage to the cerebellum have weaker conditioned eyeblinks. - The cerebellum is critical for many instances of classical conditioning where there is a short delay between the onset of the conditioned stimulus and the onset of the unconditioned stimulus. - Many instances of learning take place in other brain areas. **Types of Memory** **Short-Term and Long-Term Memory** - **Donald Hebb** proposed that there is a distinction between **short-term memory** (memory of events that have just occurred) and **long-term memory** (memory of events from further back). - Short-term memory and long-term memory differ in their capacity, reliance on rehearsal and how forgetting occurs. - Hebb suggested that **short-term memories** are stored by a reverberating circuit, where neuron A excites neuron B, which excites neuron C, which then re-excites neuron A. - He also proposed that information in **short-term memory** is **consolidated** into **long-term memory**, presumably through the building of new synapses or other structural changes. - If rehearsal of short-term memory is interrupted before consolidation is complete, the information is lost. **Changing Views of Consolidation** - Later research showed that the distinction between **short-term memory** and **long-term memory** is problematic. - Many **short-term memories** are not simply temporary stores on their way to becoming **long-term memories**. - **Consolidation** is more complex than originally thought. - The original view of consolidation was that the brain held something in short-term memory while new proteins that establish long-term memory are synthesised. Once formed, the long-term memory was believed to be permanent. - A problem with this view is that a reminder can bring an old memory into a labile state where it can be **reconsolidated**, altered or weakened. - Another problem is that the time needed for **consolidation** varies enormously. - Emotionally significant memories form quickly. - Stressful or emotionally exciting events increase the secretion of epinephrine (adrenaline) and cortisol. - Small to moderate amounts of cortisol activate the amygdala and hippocampus, where they enhance the storage and consolidation of recent events. - The amygdala stimulates the hippocampus and cerebral cortex. - Prolonged stress, which releases more cortisol, impairs memory. **Working Memory** - **A. D. Baddeley** and **G. J. Hitch** introduced the term **working memory** to replace the concept of **short-term memory**. - **Working memory** refers to how we store information while we are working with it. - One way to test **working memory** is the **delayed-response task**. - In this task, an individual sees a stimulus briefly and responds to it after a delay. - During the delay, the learner has to store a representation of the stimulus, and the prefrontal cortex is believed to be an important location for this. - Damage to the prefrontal cortex impairs performance on the **delayed-response task**. - Impairments of **working memory** are seen in older people, probably because of changes in the prefrontal cortex. - Studies on aged monkeys have shown decreases in the number of neurons and the amount of input in certain parts of the prefrontal cortex. - Older humans with declining memory show declining activity in the prefrontal cortex, but those with intact memory show greater activity than younger adults. - The increased activity in the prefrontal cortex in older people with intact memory is thought to be the brain compensating for impairment elsewhere. - Stimulant drugs that enhance activity in the prefrontal cortex improve memory in aged monkeys. **The Hippocampus** - The **hippocampus** is involved in the formation of memories and in recalling them. - People who have damage to the hippocampus have **amnesia**, which is memory loss. **People with Hippocampal Damage** - **Henry Molaison**, known in research reports as **H. M.**, had his hippocampus and some nearby structures removed to relieve epilepsy. - After the surgery, his intellect, language abilities and personality were intact. - However, he suffered from **anterograde amnesia** (inability to form memories for events that happened after brain damage) and **retrograde amnesia** (loss of memory for events that occurred before the brain damage). - His retrograde amnesia was most severe for the time leading up to the damage. - H.M. is representative of many people who have suffered amnesia after damage to the hippocampus and nearby structures. **Intact Working Memory** - H.M. was able to retain information in his **working memory**, but only if he was not distracted. - Many other people with severe amnesia also show normal working memory when not distracted. **Impaired Storage of Long-Term Memory** - H. M.\'s **long-term memory** was impaired. If his attention shifted, he would forget things within seconds. - He was unable to form new memories of personal events (episodic memories). - He did form a few new weak **semantic memories** (memories of factual information). **Severe Impairment of Episodic Memory** - H.M. had severe impairment of **episodic memory**, which is the memory of single personal events. - Patient K. C. also had an apparently complete loss of episodic memory after a motorcycle accident. - People with amnesia have difficulty imagining the future because they are impaired at recalling past events. **Better Implicit than Explicit Memory** - H.M. had better **implicit memory** than **explicit memory**. - **Explicit memory** is the deliberate recall of information that one recognises as a memory (declarative memory). - **Implicit memory** is an influence of experience on behaviour, even if you do not recognise that influence. - Another example of **implicit memory** is that amnesic patients often show preferences for people they have met before, even if they do not remember meeting them. **Intact Procedural Memory** - **Procedural memory**, which is the development of motor skills and habits, is a special type of implicit memory. - H. M. and other amnesic patients often have nearly intact procedural memory. **Theories of the Function of the Hippocampus** - There are several theories about the function of the hippocampus. **The Hippocampus and Declarative Memory** - **Larry Squire** proposed that the hippocampus is critical for **declarative memory**, especially **episodic memory**. - Studies in rats have shown that they have difficulty with tasks that require memory of a specific event, which could be considered an episodic memory. - In the **delayed matching-to-sample task**, an animal sees an object and then, after a delay, has to choose the same object from two objects. - In the **delayed non-matching-to-sample task,** the same procedure is used, except that the animal must choose the object that is different from the sample. - In both cases, the animal must remember which object was present. Hippocampal damage strongly impairs performance on these tasks. **The Hippocampus and Spatial Memory** - Another hypothesis is that the hippocampus is important for **spatial memories**. - Electrical recordings indicate that many neurons in a rat\'s hippocampus are tuned to particular spatial locations. - Similar results were found in humans. - Studies of London taxi drivers showed that answering navigation questions activated their hippocampus and that they had a larger than average posterior hippocampus. The longer they had been a taxi driver, the larger their posterior hippocampus. - These findings suggest that the adult human hippocampus can grow in response to spatial learning experiences. **Radial Maze** - The **radial maze** is a task used to test spatial memory. - A rat has to explore each arm of the maze once and only once, remembering where it has already been. - Rats with damage to the hippocampus often enter a correct arm twice, forgetting which arms they have already tried. - A virtual radial maze is used to test spatial memory in humans. - People with damage to the hippocampus are slow to learn which arms are never correct and often visit one arm multiple times before trying all the others. **Morris Water Maze** - The **Morris water maze** is another task used to test spatial memory in rats. - A rat swims through murky water to find a rest platform that is just under the surface. - Rats with damage to the hippocampus can learn to find the platform if it always starts from the same place and the platform is always in the same place. - However, they are disoriented if they have to start from a different location or if the platform moves. - Humans are sometimes tested with a virtual water maze. - People with **acute transient global amnesia** have a temporary dysfunction of the hippocampus. They are slow to learn the correct route in the virtual water maze. **The Hippocampus and Contextual Memory** - A third hypothesis is that the hippocampus is important for **memory for context**. - The hippocampus might act as a coordinator, bringing together representations from various locations in the correct order. - Recent episodic memories include much contextual detail and depend on the hippocampus. Older, less detailed memories depend mainly on the cerebral cortex, with less contribution from the hippocampus. - Studies in rats have shown that their memory for recently learned tasks depends on the context. Rats with damage to the hippocampus do not show a difference between being tested in a familiar location and another location. - Single-cell recordings in rats confirm that the hippocampus responds to context. - The three hypotheses about the function of the hippocampus are not necessarily in conflict with each other. **Other Types of Amnesia** - Other types of brain damage can cause different types of amnesia. **Korsakoff\'s Syndrome** - **Korsakoff\'s syndrome**, also known as **Wernicke-Korsakoff syndrome**, is brain damage caused by prolonged thiamine (vitamin B1) deficiency. - Thiamine is needed by the brain to metabolise glucose. - Korsakoff\'s syndrome is usually seen in chronic alcoholics. - Symptoms of Korsakoff\'s syndrome are similar to those of people with damage to the prefrontal cortex and the hippocampus. - A symptom specific to Korsakoff\'s syndrome is **confabulation**, where patients fill in memory gaps with guesses. - This mainly occurs in episodic memories. - Patients may act on their confabulations. - Confabulated answers are usually more pleasant than the actual answers. - People with Korsakoff\'s syndrome have difficulty learning lists of information because they confabulate when testing themselves and then remember their confabulation. **Alzheimer\'s Disease** - **Alzheimer\'s disease** is another cause of memory loss. - It is a progressive disease characterised by impaired memory and attention, that is most common in old age. - People with Alzheimer\'s have better procedural than declarative memory, learning new skills but not remembering learning them. - The first clue to the cause of Alzheimer\'s was the fact that people with Down syndrome almost always get Alzheimer\'s if they live into middle age. - People with Down syndrome have three copies of chromosome 21. - This led to a gene linked to early-onset Alzheimer\'s being found on chromosome 21. - Genes controlling early-onset Alzheimer\'s disease cause a protein called **amyloid-β** to accumulate both inside and outside neurons, damaging dendritic spines, decreasing synaptic input and decreasing plasticity. - As **amyloid** damages axons and dendrites, the damaged structures cluster into structures called **plaques**. - As plaques accumulate, the cerebral cortex, hippocampus and other areas atrophy. - High levels of **amyloid-β** also cause more phosphate groups to attach to **tau proteins**, which provide intracellular support to axons. - The altered tau protein starts spreading into the cell body and dendrites. - Researchers believe that altered tau also increases the production of amyloid-β, creating a vicious cycle. - The altered tau is responsible for **tangles**, structures formed from degeneration within neurons. - For Alzheimer\'s that develops after the age of 60-65, many genes increase or decrease the risk. - The most influential gene controls a chemical called **apolipoprotein E**, which helps to remove amyloid-β from the brain. - Currently, no drug is very effective in treating Alzheimer\'s disease. - The most common treatment is to give drugs that stimulate acetylcholine receptors or prolong acetylcholine release, increasing arousal. - One hypothesis for why so many drugs have proven ineffective is that by the time Alzheimer\'s is diagnosed, the damage is too extensive. - Researchers are trying to find ways to diagnose Alzheimer\'s early on. **The Basal Ganglia** - The **basal ganglia** are a group of subcortical nuclei involved in motor control, learning and other functions. - Unlike episodic memories, which develop after a single experience, the basal ganglia gradually learn what probably will or will not happen under certain circumstances. - People with damage to the basal ganglia have difficulty with complex learning tasks that require gradual learning. - People with amnesia after hippocampal damage show gradual improvement on complex tasks if they continue for a very long time, which is based on habits supported by the basal ganglia. - The basal ganglia and other brain areas, including the hippocampus and cerebral cortex, have a division of labour when it comes to learning, but nearly all tasks activate both systems. - The **basal ganglia** learn about the reward values of different actions slowly, based on the average reward over a long period. **Other Brain Areas and Memory** **Parietal Lobe** - The parietal lobe is involved in **episodic memory**. - People with damage to the **parietal lobe** have difficulty elaborating on episodic memories spontaneously, but if they are asked follow-up questions, they can answer in reasonable detail. - This suggests that their episodic memories, as well as their speech and willingness to cooperate, are intact. **Anterior Temporal Cortex** - The anterior temporal cortex is involved in **semantic memory**, which is the memory of facts and general knowledge. - People with damage to the anterior temporal cortex suffer from **semantic dementia**, which is a loss of semantic memory. - The anterior temporal cortex does not store all semantic memories. It stores some information and communicates with other brain areas. **Prefrontal Cortex** - The **prefrontal cortex** contributes to learned behaviour and decision making. - Parts of the **prefrontal cortex** are important for inhibiting inappropriate behaviours and shifting to other behaviours. - Other parts of the prefrontal cortex are involved in learning about rewards and punishments. - Unlike the **basal ganglia**, the **prefrontal cortex** learns faster and bases its decisions on the most recent events. - It is important for altering or switching responses when reward rules change. - The **ventromedial prefrontal cortex** cells respond based on the expected reward, and relay that information to the **orbitofrontal cortex**, which responds based on how a reward compares to other choices. **Key Researchers** - **Ivan Pavlov** discovered classical conditioning. - **Karl Lashley** attempted to find the **engram** by making lesions in the brains of rats. - **Richard F. Thompson** studied **classical conditioning** of eyelid responses in rabbits. - **Donald Hebb** proposed that there is a distinction between short-term memory and long-term memory. - **A. D. Baddeley** and **G. J. Hitch** introduced the term **working memory**. - **Brenda Milner** studied **H. M.** after he had his hippocampus removed. - **Larry Squire** proposed that the hippocampus is critical for declarative memory. - **Daniel Schacter** studied memory in patients with Alzheimer\'s disease. **Conclusion** The sources describe different types of memory, how memories are formed, and how different parts of the brain are involved in memory. By studying patients with amnesia, such as H.M., and conducting experiments on animals, researchers have been able to learn a lot about the biological basis of learning and memory. This knowledge is crucial for developing treatments for memory disorders, such as Alzheimer\'s disease. **Storing Information in the Nervous System** - **Not every physical change in the brain is a memory**: The challenge lies in identifying the specific changes that represent memories. - **Research into memory has had many false starts**: Many promising avenues of research turned out to be dead ends. - **Examples of abandoned research directions:** - **Penfield\'s brain stimulation studies**: While stimulation of the temporal cortex sometimes evoked vivid descriptions, these were often vague or even fabricated. They were more akin to dreams than memories, and did not provide evidence that individual neurons store specific memories. - **Learning in decapitated cockroaches**: This research showed that learning was possible in a simple nervous system, but the results were inconsistent and the learning process was very slow. - **Chemical transfer of memories**: Initial reports of memory transfer between flatworms and rats using RNA extracts sparked interest. However, these results proved to be inconsistent and ultimately failed to be replicated. **The Hebbian Synapse** - **Donald Hebb proposed a mechanism for learning at the synapse**: He suggested that when an axon repeatedly fires and activates another neuron, the connection between them strengthens. This means an axon that has successfully stimulated a cell in the past becomes even more successful in the future. - **Hebbian synapse**: A synapse that increases in effectiveness due to simultaneous activity in the presynaptic and postsynaptic neurons. - **Hebbian synapses and classical conditioning**: Pairing a weaker (conditioned stimulus) axon with a stronger (unconditioned stimulus) axon leads to an action potential in the postsynaptic neuron. This strengthens the response of the cell to the conditioned stimulus axon, eventually leading to a conditioned response. **Single-Cell Mechanisms of Invertebrate Behaviour Change** - **Aplysia as a model organism**: This marine invertebrate is well-suited for studying the physiology of learning due to its simple nervous system, large neurons, and the fact that its neurons are nearly identical across individuals. - **Habituation in Aplysia**: Repeated stimulation of the Aplysia\'s gills with a water jet leads to a decrease in the withdrawal response. This habituation is not due to muscle fatigue or changes in the sensory neuron. Instead, it is caused by changes in the synapse between the sensory and motor neurons, leading to decreased neurotransmitter release. - **Sensitization in Aplysia**: A strong stimulus anywhere on the Aplysia\'s skin intensifies subsequent withdrawal responses to touch. - **Mechanism of sensitization**: A strong stimulus activates a facilitating interneuron that releases serotonin onto the presynaptic terminals of sensory neurons. Serotonin blocks potassium channels, prolonging the action potential and increasing neurotransmitter release. This process eventually leads to the synthesis of new proteins that contribute to long-term sensitization. **Long-Term Potentiation in Vertebrates** - **Long-term potentiation (LTP)**: A lasting increase in the responsiveness of a synapse after a brief but intense series of stimuli. It is considered a potential cellular basis for learning and memory. - **Properties of LTP**: - **Specificity**: Only active synapses are strengthened. - **Cooperativity**: Simultaneous stimulation by multiple axons produces LTP more strongly than repeated stimulation by a single axon. - **Associativity**: Pairing a weak input with a strong input enhances later responses to the weak input. - **Long-term depression (LTD)**: A prolonged decrease in response at a synapse that occurs for less active axons. It acts as a compensatory process to balance the strengthening of other synapses. **Biochemical Mechanisms of LTP** - **AMPA and NMDA receptors**: LTP primarily involves changes at glutamate synapses, specifically at AMPA and NMDA receptors. - **AMPA receptors** open sodium channels when activated by glutamate. - **NMDA receptors** are blocked by magnesium ions at resting potential. They only open when the membrane is depolarized, allowing both sodium and calcium to enter. - **Calcium\'s role in LTP**: The influx of calcium through NMDA receptors activates a protein called CaMKII, which triggers a series of reactions leading to the release of CREB. - **CREB\'s role**: CREB regulates gene expression, potentially leading to long-term changes in synaptic strength. - **BDNF\'s role**: Brain-derived neurotrophic factor (BDNF) contributes to LTP by promoting synapse growth and increasing neurotransmitter release. - **Consequences of LTP**: - Increase in AMPA receptor number or sensitivity - Growth of dendritic branches and spines, forming new synapses - Increase in NMDA receptors - **NMDA-independence of established LTP**: Once LTP is established, blocking NMDA receptors does not affect its maintenance. - **Presynaptic changes in LTP**: Retrograde transmitters, like nitric oxide (NO), travel back to the presynaptic neuron and cause changes such as increased neurotransmitter release and axon expansion. **Improving Memory** - **Pharmacological approaches**: - **Stimulant drugs**: Moderate doses of stimulants like caffeine, amphetamine, and methylphenidate can enhance memory storage by increasing arousal. - **Acetylcholine facilitators**: Drugs that increase acetylcholine levels are used in Alzheimer\'s disease to improve memory. - **Ginkgo biloba**: This herb has been marketed for memory enhancement, but research has not consistently shown benefits. - **Bacopa monnieri**: Some studies suggest this herb may have mild memory-enhancing effects, but more research is needed. - **Genetic modifications**: While genetic modifications have shown promise in enhancing memory in rodents, these methods often come with negative side effects. - **Behavioural methods**: The most effective way to improve memory is through proper learning techniques, rehearsal, and self-testing. - **Other strategies**: - **Computer-based cognitive training**: Some software programmes have been shown to improve memory and cognition in older adults. - **Physical exercise**: Regular physical activity can also enhance memory, particularly in older age. **The Seeing Brain** **From Eye to Brain** The eyes are crucial for vision, but the brain ***actively constructs*** a visual representation of the world. The brain ***makes inferences***, going beyond the raw information given. ***Sensation*** is the effect of a stimulus on sensory organs, while *perception* is the elaboration and interpretation of that stimulus. The ***retina*** converts light into neural signals using photoreceptors: ***rod cells*** (low light) and ***cone cells*** (daytime and colour). The ***fovea*** has the highest concentration of cones, providing the greatest visual acuity. ***Bipolar cells*** in the retina detect light or dark areas on contrasting backgrounds. ***Retinal ganglion cells*** have ***centre-surround receptive fields*** and respond to differences in light. The ***blind spot*** is where the optic nerve leaves the eye, lacking photoreceptors, but the brain fills in the missing information. The dominant pathway for visual perception is the ***geniculostriate route***, which goes through the ***lateral geniculate nucleus (LGN)*** in the thalamus to the *primary visual cortex (V1)*. V1, also called the ***striate cortex***, transforms information from the LGN into a basic code for further processing. The LGN segregates information from both eyes into six layers: ***parvocellular (P layers)*** (detail and colour) and ***magnocellular (M layers)*** (movement). A third type of LGN cell, ***konio (K)***, has less functional specificity. V1 neurons represent lightness, colour, edges, movement, and depth. ***Simple cells*** in V1 respond to lines of specific orientations and wavelengths. ***Complex cells*** combine simple cell responses, are orientation-selective, have larger receptive fields, and require stimulation across their entire length. ***Hypercomplex cells*** are built from complex cells, sensitive to orientation and length. Visual processing is ***hierarchical***, but information also flows back down. The visual system has multiple pathways with different functions. The pathway to the ***suprachiasmatic nucleus (SCN)*** regulates the biological clock. Pathways via the ***superior colliculus*** and *inferior pulvinar* are important for orienting to stimuli and provide early warning signals. An alternative pathway from the LGN (via K-cells) projects to the ***motion processing area V5/MT*** bypassing V1. **Cortical Blindness and Blindsight** \* Damage to one side of V1 causes ***cortical blindness*** (***hemianopia***) in the opposite visual field. \* Partial V1 damage can result in ***quadrantanopia*** (blindness in a quarter of the visual field) or a ***scotoma*** (a smaller blind region). \* V1 is ***retinotopically organized***: the layout of information reflects the retina\'s spatial organization. \* ***Blindsight*** is the ability to respond to visual stimuli in the \"blind\" area without conscious awareness. \* Blindsight patients may perform discriminations (e.g., orientation, motion, contrast) well above chance while feeling like they are guessing. \* Blindsight is likely due to other visual pathways bypassing V1. \* Blindsight demonstrates the importance of both conscious and unconscious visual processes. \* Unconscious routes are less efficient and only capable of coarse discriminations. **Functional Specialization of the Visual Cortex Beyond V1** \* The ***ventral stream*** (temporal lobes) is involved in object recognition, while the ***dorsal stream*** (parietal lobes) is involved in action and attention. \* The ***extrastriate cortex*** (outside V1) has increasingly broader receptive fields and specialized areas. \* ***V4*** is the main colour centre, and lesions to it cause \*\*cerebral achromatopsia\*\* (seeing in grayscale). \* V4 is crucial for ***colour constancy***: perceiving consistent surface colour under different lighting conditions. \* V4 neurons compare wavelengths across receptive fields to achieve colour constancy. \* V4 also processes shape and texture, and other brain regions contribute to colour processing (e.g., the hippocampus for memory). \* ***V5/MT*** is the main motion centre, and lesions cause ***akinetopsia*** (inability to perceive visual motion). \* Other pathways process specific types of motion, such as \*\*biological motion\*\*. \* ***Supramodal regions*** in the parietal cortex respond to motion across different senses. \* Beyond V1, the brain \"divides and conquers\" visual information, processing different attributes in specialized regions. **Recognizing Objects** \* Object recognition connects visual information with accumulated knowledge. \* The process involves multiple stages:     1. Detecting basic elements (edges, bars).     2. Grouping elements into higher-order units (depth, figure-ground segregation), potentially influenced by top-down knowledge.     3. Matching viewer-centered descriptions to stored three-dimensional structural descriptions, achieving object constancy.     4. Attributing meaning to the stimulus. \* ***Visual agnosia*** refers to disorders of object recognition. \* ***Apperceptive agnosia*** involves deficits in perceptual processing, while ***associative agnosia*** involves deficits in semantic memory. \* ***Gestalt principles*** explain how features are grouped into wholes.     \* ***Law of proximity***: closer elements are grouped.     \* ***Law of similarity***: elements sharing attributes are grouped.     \* ***Law of good continuation***: edges are grouped to avoid changes.     \* ***Law of closure***: missing parts are filled in.     \* ***Law of common fate***: elements moving together are grouped. \* Perceptual grouping occurs at various levels in the visual hierarchy. \* The ***lateral occipital complex (LOC)*** is involved in computing object shape, responding to objects more than textures. \* ***Integrative agnosia*** is a failure to integrate parts into wholes (e.g., case HJA). \* ***Object constancy*** is recognizing an object across different viewpoints and conditions. \* ***Viewpoint-invariant theories*** suggest direct mapping of object parts to structural descriptions. \* ***Viewpoint-dependent theories*** suggest mental rotation to a standard viewpoint. \* The ***inferotemporal cortex (IT)*** codes information for object constancy. \* The ***left inferotemporal (fusiform) region*** responds regardless of viewpoint or size. \* ***Adaptation*** (repetition suppression) in fMRI studies reveals brain regions tuned to specific object features. \* ***Category specificity*** proposes that the brain represents different categories in distinct ways. \* Specialized areas for visual recognition include:     \* ***Parahippocampal place area (PPA)***: scenes     \* ***Extrastriate body area (EBA)***: human body ***Recognizing Faces*** \* Face recognition may differ from general object recognition:     \* Goal: identify specific individuals     \* Faces may require special processing or belong to a distinct category \* The ***Bruce and Young model*** (1986):     \* Early processing: view-dependent structural description     \* Familiar faces: matched to ***face recognition units (FRUs)***, then ***person identity nodes (PINs)*** for semantic and name information     \* Unfamiliar faces: processed via ***directed visual processing***     \* Parallel routes for expression, age, gender, and lip-reading \* The ***Haxby et al. model*** (2000):     \* Core regions: ***fusiform face area (FFA)*** (familiar faces) and ***superior temporal sulcus (STS)*** (dynamic aspects)     \* Extended system: other brain areas connected to the core system \* Evidence for face specificity:     \* Distinct neural substrate     \* Selective impairment (***prosopagnosia***) \* FFA shows ***categorical perception*** for faces. \* Why are faces special?     \* ***Task difficulty***: refuted by patients with visual agnosia without prosopagnosia     \* ***Holistic vs. part-based processing***: faces may rely more on holistic processing, but evidence is mixed     \* ***Visual expertise***: within-category discrimination and expertise with thousands of exemplars     \* ***Distinct category***: evidence from dissociations and congenital prosopagnosia **Vision Imagined** \* Visual imagery likely uses visual representations. \* V1 activity during imagery suggests its involvement. \* Different imagery content activates specific visual areas (e.g., LOC for shape, V5/MT for motion). \* Visual imagery and perception can dissociate (e.g., agnosia patients with good imagery). \* Top-down access to structural descriptions may explain this dissociation. ***Summary*** \* V1 processes basic visual features and is crucial for conscious vision. \* Blindsight reveals unconscious visual pathways. \* Extrastriate regions specialize in processing specific attributes (e.g., colour, motion). \* Object constancy is achieved through matching visual features to stored representations or mental rotation. \* Faces may be processed differently due to holistic processing, expertise, or being a distinct category. \* Mental imagery shares resources with perception and can be fractionated similarly. **Module 1: Cells of the Nervous System** - **Neurons:** - The communicators of the nervous system, responsible for receiving, processing, and transmitting information. - **Structure:** - **Dendrites:** Receive incoming information from other neurons. The extent of branching indicates the number of connections. - **Soma (cell body):** Contains genetic material and metabolic machinery. - **Axon:** Sends information to other neurons. Many axons are covered in **myelin**, which speeds up transmission. - The **axon terminal** is the end of the axon, where neurotransmitters are released. - **Types:** - **Unipolar:** One process emanating from the cell body. - **Bipolar:** Two processes emanating from the cell body. - **Multipolar:** Numerous processes extending from the cell body. This is the most common type. - **Interneurons:** Neurons with no axons or very short axons that integrate information within a structure. - **Glia:** - Support cells of the nervous system. - **Types:** - **Astrocytes:** - Star-shaped, largest glia that fill the space between neurons. - Form the **blood-brain barrier**, provide nutrients, regulate the chemical environment, and may play a role in information transmission. - **Oligodendrocytes:** - Produce **myelin** to insulate axons in the brain and spinal cord, speeding up information transfer. - **Microglia:** - Smallest glia that act as phagocytes, removing debris from the nervous system. - Excessive activation may be implicated in neurodegenerative diseases. - **Communication within the Neuron:** - **Resting potential:** -70 mV, maintained by uneven distribution of ions (sodium - Na+ and potassium - K+) across the membrane. - The **sodium-potassium pump** actively maintains the ion gradient. - **Action potential:** - Triggered when neurotransmitters open ion channels, allowing Na+ influx and K+ efflux. - **Depolarization:** The membrane potential becomes more positive, reaching +50 mV. - **Repolarization:** Return to the resting potential of -70 mV. - **Hyperpolarization:** Temporary overshoot of the resting potential. - **All-or-none:** Once triggered, the action potential occurs at a uniform size. - **Absolute refractory period:** A period when another action potential cannot be triggered due to closed sodium channels. - **Saltatory conduction:** Action potentials jump between **nodes of Ranvier** in myelinated axons, speeding up transmission. - **Communication between Neurons:** - **Synapse:** The gap between neurons where chemical communication occurs. - **Presynaptic events:** - Arrival of an action potential at the axon terminal opens calcium (Ca2+) channels. - Ca2+ influx triggers **exocytosis**, releasing neurotransmitters from vesicles into the synapse. - **Postsynaptic events:** - Neurotransmitters bind to receptors on the postsynaptic membrane. - **Receptor types:** - **Ionotropic (transmitter-gated ion channels):** Fast-acting, control ion channels directly. - **EPSP (excitatory postsynaptic potential):** Depolarization of the dendrite, moving it closer to an action potential. - **IPSP (inhibitory postsynaptic potential):** Hyperpolarization of the dendrite, moving it further from an action potential. - **Metabotropic (G-protein-coupled receptors):** Slower, more diverse, and longer-lasting responses. - Activate G-proteins, which can influence ion channels, gene expression, and other intracellular processes. - **Termination of neurotransmitter action:** - **Reuptake:** Presynaptic neuron reabsorbs the neurotransmitter. - **Enzymatic degradation:** Neurotransmitter is broken down into inactive forms. **Module 2: The Nervous System** - **Anatomical Directions:** - **Neuraxis:** An imaginary line through the spinal cord and brain. - **Dorsal:** Toward the back (top of the brain, back of the spinal cord). - **Ventral:** Toward the front (bottom of the brain, front of the spinal cord). - **Anterior:** Toward the head (front of the brain, top of the spinal cord). - **Posterior:** Toward the tail (back of the brain, bottom of the spinal cord). - **Superior:** Above or topmost. - **Inferior:** Below or bottommost. - **Medial:** Toward the middle. - **Lateral:** Away from the middle (toward the outside). - **Ipsilateral:** On the same side. - **Contralateral:** On opposite sides. - **Planes of Section:** - **Horizontal:** Parallel to the ground. - **Sagittal:** Parallel to the side of the brain (midsagittal is directly down the middle). - **Coronal:** Parallel to the face (also called frontal or transverse). - **Divisions of the Nervous System:** - **Central nervous system (CNS):** Brain and spinal cord. - **Peripheral nervous system (PNS):** All nerves outside the brain and spinal cord, further divided into: - **Somatic nervous system (SNS):** Interacts with the external environment (sensory and motor nerves). - **Autonomic nervous system (ANS):** Regulates internal states, divided into: - **Sympathetic:** Prepares the body for action (\"fight or flight\"). - **Parasympathetic:** Supports non-emergency functions (\"rest and digest\"). - **The Spinal Cord:** - 31 segments, each with a pair of spinal nerves. - **Bell-Magendie law:** Dorsal roots carry sensory information, ventral roots carry motor information. - **The Brain:** - **Hindbrain (rhombencephalon):** - **Myelencephalon:** - **Medulla oblongata:** Regulates vital functions (breathing, heart rate). - **Metencephalon:** - **Pons:** Relays information between the cerebellum and other brain structures. - **Cerebellum:** Coordinates movement, may also be involved in language and other cognitive functions. - **Midbrain (mesencephalon):** - **Tectum:** - **Superior colliculi:** Visual reflexes. - **Inferior colliculi:** Auditory reflexes. - **Tegmentum:** - **Substantia nigra:** Motor control, degenerates in Parkinson\'s disease. - **Red nucleus:** Motor nucleus. - **Periaqueductal gray:** Pain perception. - **Forebrain (prosencephalon):** - **Diencephalon:** - **Thalamus:** Sensory and motor relay station, contains many specialized nuclei. - **Hypothalamus:** Regulates autonomic and endocrine systems, controls the pituitary gland, involved in basic drives and behaviours (the four Fs). - **Telencephalon:** - **Cerebral cortex:** Largest part of the brain, responsible for higher cognitive functions. - **Lobes:** Frontal, parietal, temporal, occipital. - **Basal ganglia:** Caudate nucleus, putamen (together called the striatum), and globus pallidus. - Involved in movement initiation and control, affected in Parkinson\'s and Huntington\'s diseases. - **Limbic system:** Amygdala, hippocampus, fornix, cingulate cortex, mammillary bodies. - Involved in emotion, motivation, memory, and response selection. - **Connections between Hemispheres:** - **Commissures:** Structures that connect the two hemispheres. - **Corpus callosum:** Largest commissure, connects cortical areas between hemispheres. - **Cranial Nerves:** - 12 pairs of nerves that emerge from the brain. - Carry sensory and motor information for the head and some internal organs. - See Table 1 in the source for a list of cranial nerves and their functions. - **Blood Supply:** - Brain receives 20% of blood flow and consumes 25% of the body\'s energy. - **Vertebral arteries:** Supply posterior brain regions. - **Internal carotid arteries:** Supply anterior brain regions. - **Circle of Willis:** Connects the major arteries, provides redundancy and pressure equalization. - **Protection:** - **Bone (skull and spinal column):** Provides physical protection. - **Meninges:** Three protective membranes: - **Dura mater:** Outermost, tough layer. - **Arachnoid mater:** Middle, weblike layer. - **Pia mater:** Innermost, delicate layer. - **Cerebrospinal fluid (CSF):** Cushions and supports the brain, helps remove waste, and may be involved in chemical communication. - Found in the subarachnoid space and ventricles. - **Ventricles:** Four fluid-filled cavities within the brain. - **Hydrocephalus:** Condition caused by blockage of CSF flow, can lead to brain damage. - **Blood-brain barrier:** Two layers of cells that limit the passage of substances from the bloodstream into the brain. - Protects the brain but can hinder drug delivery. **Current Controversy: Are You Really Born With All the Neurons That You Will Ever Have?** - For many years, neuroscientists believed that the human brain did not generate new neurons after birth. - Recent research has shown that neurogenesis, the formation of new neurons, does occur in the adult hippocampus. - This discovery has implications for the potential to treat brain injuries and neurodegenerative diseases. **The Executive Brain** - The brain\'s executive functions can be understood as the set of complex processes that an individual uses to optimise their performance in situations that require the operation of a number of cognitive processes. - A metaphor for executive functions is that they are the brain\'s conductor, which instructs other regions to perform, or be silenced, and generally coordinates their synchronised activity. - Executive functions are not tied to a single cognitive domain (memory, language, perception, and so on). - Instead, they take on a meta-cognitive, supervisory, or controlling role. - Executive functions have traditionally been associated with the frontal lobes, and problems with executive functions have been called "frontal lobe syndrome". - More accurately, executive functions are associated with the **prefrontal cortex (PFC)** of the frontal lobes. - Whether all aspects of executive function can be localised to the prefrontal cortex remains an empirically open question. **Anatomical and Functional Divisions of the Prefrontal Cortex** - Before discussing executive functions, it\'s worth reviewing the anatomy of the prefrontal cortex. - Enlargement of the frontal cortex in mammals shows an evolutionary progression (though brain size does not necessarily correlate with intelligence). - In humans, the frontal lobes, and particularly the prefrontal cortex, are much larger than in other animals. - In humans, the frontal lobes occupy almost a third of the cortical volume. - The prefrontal cortex has three surfaces: - The **lateral** surface - The **medial** surface - The **orbitofrontal** surface **Executive Functions in Practice** - Patients with frontal lobe damage are impaired on tests of "fluid intelligence". - Fluid intelligence is the ability to solve novel problems and is often contrasted with crystallised intelligence which is the sum of an individual\'s knowledge. - **Koechlin and Summerfield (2007) propose a hierarchical model of executive function that runs from the premotor cortex (posteriorly) to the frontal poles (anteriorly):** - At the lowest level is the premotor cortex which implements simple stimulus-response mappings. - An example is: "press the left button when you see red, and right for green". - The next level involves adding **contextual information** to the stimulus-response mappings. - An example is: "perform consonant/vowel discrimination for red letters and UPPER/lower case discrimination for green letters". - This level requires what Koechlin and Summerfield (2007) term **cognitive control** to be implemented. - The next level requires switching instructions on a block-by-block basis (e.g. so that red becomes the UPPER/low task and green the consonant/vowel task). - This requires what Koechlin and Summerfield (2007) term **episodic control** which is knowing which context to apply at a given moment in time. - **The highest level in their model, termed "branching control," involves holding in mind pending tasks while carrying out an ongoing task (i.e. multi-tasking).** - In an fMRI study, Koechlin et al. (2003) compared the first three types of situation (sensorimotor rules, contextual rules, episodic rules) using the letter and colour stimuli described above. - Implementing the sensorimotor rules invoked the premotor cortex. - The presence of contextual rules invoked more anterior activity in the brain. - The presence of episodic rules was associated with activity in the most anterior part of the prefrontal cortex. - Patients with lesions limited to the frontal poles are impaired on tasks of multi-tasking and on tasks of social cognition (theory-of-mind, understanding faux pas). - However, these patients perform well on many other tests of executive function. **Hemispheric Differences** - Functional differences between the left and right lateral prefrontal cortex are more controversial than other organisational principles discussed in Chapter 14. - These differences are not usually found in single-cell recordings from the monkey prefrontal cortex. - This may not be surprising since humans are known to show more lateralisation of higher cognitive functions than other primates. - Hemispheric differences are also less apparent in functional imaging data from humans. - **Perhaps the most convincing evidence comes from neuropsychological investigations of lesions to the prefrontal cortex. These studies have shown some reliable functional differences between the hemispheres.** - Even here, it is important to note that the dissociations tend to be relative rather than absolute. - Patients with left and right prefrontal cortex lesions will be impaired on different tasks, but both groups will be impaired relative to controls. **Summary and Key Points of the Chapter** - Executive functions are needed to optimise performance when: - Several cognitive processes need to be coordinated. - A situation is novel or difficult. - A situation does not require an automatic response (troubleshooting, problem-solving). - The role of executive functions is typically described as "supervisory" or "controlling." - Functional imaging studies and studies of brain-damaged patients suggest that the prefrontal cortex plays a key role in executive functions. - Patients with lesions to the prefrontal cortex may have difficulties with problem-solving, overcoming habitual responses, multi-tasking, and so on. **The Origins of Cognitive Neuroscience** - Before the development of the scientific method, **early understanding of the mind and cognition was primarily derived from philosophical inquiry** rather than empirical observation. - **Rationalism**, championed by figures like Plato and Descartes, posits that knowledge originates from reason, independent of sensory experiences. - Conversely, **empiricism**, advocated by John Locke and Francis Bacon, asserts that knowledge is gained through sensory experiences and observations. - **The evolution of empiricism led to the development of the scientific method, which relies on sensory input, measurable observations, and the formulation of testable predictions to investigate phenomena and generate knowledge.** - Early psychology depended on introspection, but with advancements in empirical science, it shifted towards scientific methodologies. - **Cognitive psychology emerged in the mid-20th century, focusing on measurable aspects of cognition and bridging the gap between introspection and empirical research.** **Localisation Theories** - **Claudius Galen\'s observations of gladiators with head injuries suggested that the brain, not the heart, is the centre of thought and sensation.** - **Franz Gall\'s phrenology, though flawed, popularised the idea of functional localisation, proposing that different brain areas have specific functions.** - **Pierre Flourens and Friedrich Goltz challenged phrenology through lesion studies, demonstrating that the brain functions more holistically.** - **Paul Broca and Carl Wernicke\'s discoveries of brain areas associated with speech production (Broca\'s area) and language comprehension (Wernicke\'s area) provided strong support for the localisation of brain functions.** - The concept of **double dissociation**, exemplified by the distinct roles of Broca\'s and Wernicke\'s areas in language, suggests that separate neural systems govern different cognitive functions. **Luria\'s Pluripotentiality** - **Alexander Luria\'s concept of pluripotentiality proposes that brain areas can be involved in multiple cognitive processes.** - **Luria emphasised the interconnectedness of the brain, suggesting that different regions can compensate for each other in case of damage.** - **His work highlighted the brain\'s plasticity, its capacity to adapt and reorganise itself due to injury or environmental changes.** **Research Methodologies** - **Dissociation methods**, such as the double dissociation observed with Broca\'s and Wernicke\'s aphasia, demonstrate that damage to one area impairs a specific function while sparing another. - **Association methods** reveal that damage to a single area, like the prefrontal cortex, can lead to impairments in multiple, related functions (e.g. working memory, decision-making, inhibitory control), suggesting these functions rely on shared neural systems. - **Luria\'s theory of functional systems shifted focus from localisation to understanding distributed processing in the brain.** - **Cognitive functions arise from interconnected networks rather than isolated areas.** - **Pluripotentiality and neuroplasticity allow brain areas to perform diverse functions or adapt to new ones.** **Correlational Methods** - **Correlational methods in cognitive neuroscience investigate the relationships between brain structure/activity and behaviour, but do not establish causality.** - **These methods are crucial for linking neural structures to cognitive functions.** - **Common correlational methods include:** - **Anatomical methods:** - **Animal Models:** Experiments on animals allow for controlled manipulations (e.g. lesions) to examine how brain regions relate to behaviour. Examples include John O\'Keefe\'s research on \"place cells\" in the hippocampus and May-Britt and Edvard Moser\'s work on \"grid cells.\" - **Post-Mortem Examinations:** Examining the brains of individuals with brain injuries can provide insights into brain-behaviour relationships. Famous examples include studies on Henry Molaison (HM) and Phineas Gage. - **Behavioural methods:** - **Cognitive Assessments:** Cognitive tasks, often paired with neuroimaging, are used to measure specific cognitive processes and correlate them with brain activity. - **Functional Neuroimaging:** Techniques like fMRI, EEG, and TMS are used to measure brain activity during tasks to understand the neural correlates of cognition. - **Important issues to consider with correlational methods**: - **Practice effects** (improvement due to repeated exposure to tasks) - **Ecological validity** (generalisability of lab findings to real-world settings) - **Ethical concerns** (especially with animal research) - **Cross-species translation** (applying findings from animal studies to humans) - **Indirect measurement** (inferring brain activity from indirect measures like blood flow) **Causal Methods** - **Causal methods in cognitive neuroscience aim to establish direct links between brain activity and cognitive functions.** - They involve manipulating brain regions or neurotransmitter systems and observing the resulting behavioural changes. - **Common causal methods**: - **Transcranial Magnetic Stimulation (TMS):** Non-invasive technique using magnetic fields to stimulate or inhibit specific brain areas, allowing researchers to examine the causal role of those areas in cognitive functions. TMS has been used to treat conditions like major depressive disorder and obsessive-compulsive disorder. - **Drug Administration:** Manipulating neurotransmitter systems by administering drugs (agonists to enhance or antagonists to inhibit) allows researchers to study their effects on cognition and behaviour. **Structural, Functional, and Connectionist Neuroimaging** - **Structural neuroimaging techniques** visualise the physical structures of the brain. - **Computed Tomography (CT):** Uses X-rays to create cross-sectional images, good for detecting structural abnormalities like tumours, strokes, or injuries. - **Magnetic Resonance Imaging (MRI):** Uses magnetic fields and radiofrequency pulses to create detailed images, useful for detecting structural abnormalities and lesions, as well as cortical thickness and grey/white matter abnormalities. - **Functional neuroimaging techniques** measure brain activity, either by tracking blood flow or electrical activity. - **Blood Flow-Related Techniques**: - **Functional Magnetic Resonance Imaging (fMRI):** Measures changes in blood oxygen levels (BOLD signal) as a proxy for neuronal activity, providing good spatial resolution for identifying active brain regions during tasks. - **Positron Emission Tomography (PET):** Uses radioactive tracers to track metabolic activity in the brain, commonly used in research on neurodegenerative diseases, tumour detection, and psychiatric disorders. - **Near-Infrared Spectroscopy (NIRS/fNIRS):** Uses near-infrared light to measure changes in blood oxygenation, providing a portable and less invasive way to study brain function, particularly in infants and young children. - **Electrical Activity-Related Techniques**: - **Electroencephalography (EEG):** Measures electrical signals (neural oscillations) produced by brain cells using electrodes on the scalp, excellent for tracking the timing of brain processes. - **Magnetoencephalography (MEG):** Detects magnetic fields generated by the electrical activity of neurons, offering better spatial precision than EEG and is useful for studying sensory processing and brain pathology. - **Connectionist neuroimaging techniques** examine brain connectivity, the structural or functional relationships between different brain regions. - **Diffusion Tensor Imaging (DTI):** Measures water diffusion in the brain to map white matter tracts (structural connections), useful for studying disorders like multiple sclerosis and traumatic brain injury.