Lecture 2 Handout Slides PDF

9/29/2022 CHAPTER 3 Methods of Cognitive Neuroscience Cognitive Neuroscience, 5 th edition © 201...

9/29/2022 CHAPTER 3 Methods of Cognitive Neuroscience Cognitive Neuroscience, 5 th edition © 2019 by W. W. Norton & Company 1 Topics today: What is the main topic of Cognitive Psychology? Single cell electrophysiology Neurology (Neuropsychology) Transcranial magnetic stimulation Imaging/functional imaging 2 What does Cognitive Psychology do? Stuff happens See/hear/feel → → → act (do something) Mental representations Mental operations 3 1  9/29/2022 Cognitive Psychology tries to understand: 1. mental processes/mental operations. 2. mental representations. Cognitive Neuroscience tries to understand the underlying substrate and mechanisms of: 1. mental processes. 2. mental representations. 4 What is a mental representation? Anything that ‘means’ something to the individual. e.g. the concept of a ‘tree’ is a mental representation (when we see it we know it). But we have multiple levels of knowledge: We know a tree from seeing it. a carpenter would know a tree from smelling the wood. We know it when we see the word ‘tree’. 5 How are mental processes and mental representation linked? It is actually very simple: 1. Your eyes process the incoming light (e.g. of a tree), 2. your visual system processes the information (i.e. a basic mental process takes place), 3. you see the tree (one form of a mental representation). 4. Seeing the tree triggers a mental process (e.g. ‘avoid’ if you drive a car). 6 2  9/29/2022 How does Cognitive Psychology study mental representations and operations? Posner’s Letter-matching task. In this version of the task, the subject responds “same” when both letters are either vowels or consonants and “different” when they are from different categories. 7 Posner’s letter matching task Letter-matching task. The reaction times vary for different conditions. Chronometry: using time measures (reaction times) to infer the workings of the brain 8 Posner argued that the different latencies reflect the degree of processing required to do the letter matching task. It follows that stimulus identity representations are activated first, phonetic representations are activated second, while categorizations are activated last. Thus it is possible to dissect which mental representations differ from one another, and how complex they are in terms of mental processing. 9 3  9/29/2022 Can we demonstrate that during processing representations are transformed? 10 Posner’s letter matching task: Version 2 The same letter-matching task as previously, except that an interval, defined as the stimulus onset asynchrony, separates the presentation of the two letters. 11 Posner’s letter matching task: Version 2 As this interval is lengthened, the difference in the reaction time to the physical-identity and phonetic-identity conditions becomes smaller, suggesting a transformation of the representation into a more abstract code. 12 4  9/29/2022 Can we usefully subdivide mental operations? 13 Subdividing mental operations: Memory comparison task The subject is shown a set of one, two, or four letters and is asked to memorize them. After a delay, a single probe letter appears, and the subject indicates whether that letter was a member of the memory set. 14 Subdividing mental operations: Memory comparison task Performance of this task is hypothesized to require four different mental operations 15 5  9/29/2022 Subdividing mental operations: Memory comparison task Reaction time increases with set size, indicating that the target letter must be compared with the memory set sequentially rather than in parallel. 16 Experimental techniques informing Cognitive neuroscience Animal research Neurology Brain imaging 17 Single-Cell Recordings Humans Animals Occasionally used in treating Extensively used in a variety of epilepsy of the medial temporal visual and auditory tasks lobe (MTL) 18 18 6  9/29/2022 19 Animal research The morality of using animals for research purposes has been debated for centuries. People on both sides of the debate have recognized the importance of engaging the public—a point underscored by the fact that members of the U.S. Congress receive more letters on this issue than on any other. 20 Animal research 1. Who believes animal research is ethically questionable? 2. Who believes that animals are used for medical research in the UK? 3. Who believes that animals are used for cosmetic testing in the UK? 4. Who believes that animals are used for basic research in this country? 5. Do you think all animal research should be banned in the UK? 6. Do you think that animal research is less strictly regulated in the UK than animal usage for food production (farming)? 7. If you are opposed to animal research, would you be prepared to refuse medication (developed through animal research) if seriously ill? 21 7  9/29/2022 Neurology Trauma Stroke, vascular disorders Tumors Neurodegenerative diseases Infectious disorders Functional neurosurgery 22 Prominent Degenerative and Infectious Disorders of the Central Nervous System 23 Neurological Dysfunction Alzheimer’s Disease Stroke 24 24 8  9/29/2022 Traumatic Brain Injury 25 25 A widely used methods: Electroencephalogram (EEG) EEG electrodes attached to the head all to measure electrical activity in the brain. It is used for many different purposes, e.g. epilepsy or cognitive neuroscience. 26 Example EEG traces from 6 different skull electrodes Electroencephalographic recordings from six electrodes, positioned over the frontal (F), temporal (T), and occipital (O) cortex on both the left (L) and the right (R) sides. Activity during normal cerebral activity. 27 9  9/29/2022 Same as last slide, but this shows activity during a grand mal epileptic seizure Electroencephalographic recordings from six electrodes, positioned over the frontal (F), temporal (T), and occipital (O) cortex on both the left (L) and the right (R) sides. Activity during a grand mal seizure. 28 ERP ERP and Electrocorticogram (ECoG) 29 29 Functional neurosurgery Life magazine cartoon from 1947, sketching the mechanisms underlying the supposed benefits of the frontal lobotomy. Freudian theory was in its heyday at the time, as reflected in the accompanying caption, which read, “In agitated depression (top drawing), the superego becomes overbearing and unreasonable, unbalancing the whole mind.... The surgeon’s blade, slicing through the connections between the prefrontal areas (the location of the superego) and the rest of the brain, frees the tortured mind from its tyrannical ruler (bottom drawing).... Lobotomy, however, should be performed only on those patients whose intelligence is sufficient to take control of behavior when the moral authority is gone.” 30 10  9/29/2022 Functional neurosurgery Definition: Altering the activity of a brain area by either using ablation (removing), electrical or pharmacological methods to establish overall more normal patient function. It is widely used in (examples): Movement disorders (e.g. Parkinson, deep brain stimulation) Psychiatric disorders (depression, obsessive compulsive). Chronic pain Epilepsy Brain tumors. 31 Inferences from neurological lesions A lesion causes a deficit It follows that the lesioned area performs the task of interest. No! not a valid conclusion! Any cognitive task requires a variety of subtasks to be successfully performed Single vs. double dissociations 32 Hypothetical series of results conforming to either a single (a) or a double (b) dissociation. With the single dissociation, the patient group shows impairment on one task and not on the other. With the double dissociation, one patient group shows impairment on one task and a second patient group shows impairment on the other task. Double dissociations provide much stronger evidence for a selective impairment. 33 11  9/29/2022 What can cause brain damage? (4-5 examples) 34 Correlation and Causation PTSD and Brain Size 35 35 Single vs. group studies Drawing inferences from the study of humans with brain damage is difficult because naturally occurring brain lesions are never identical. Group studies can facilitate the functional analysis of brain structures by identifying regions of lesion overlap. Shown here are sketches of the extent of lesions in seven patients who had strokes in the frontal lobe of the left hemisphere. The individual patients are represented in each row, with the transverse slices going from inferior to superior (as the upper left diagram shows). The bottom row shows the extent of damage for the group in composite form. 36 12  9/29/2022 Optogenetics Using Light to Manipulate Neuronal Activity 37 37 Noninvasive Stimulation Methods Transcranial Magnetic Stimulation (TMS) o Low-level currents that result in action potentials under the anodes 38 38 39 13  9/29/2022 Functional magnetic resonance imaging (fMRI) 40 Functional magnetic resonance imaging (fMRI) 41 Magnetic Resonance Imaging MRI 42 42 14  9/29/2022 Functional magnetic resonance imaging (fMRI) fMRI measures changes in blood flow/volume that are induced by neuronal activity (mental activity). 43 Combined use of fMRI and TMS to demonstrate the role of the visual cortex in tactile perception. Functional MRI showing areas of activation in nine people during tactile exploration with the eyes closed. All of the subjects show some activation in striate and extrastriate cortex. 44 Combined use of fMRI and TMS to demonstrate the role of the visual cortex in tactile perception. The results graphed here illustrate accuracy in making tactile orientation judgments when a textured object is vibrated against the right index finger. Performance is impaired when the TMS pulse is applied 180 ms after the vibration. This effect is observed only when the pulse is applied over the central occipital cortex or over the contralateral occipital lobe. 45 15  9/29/2022 1) Transcranial magnetic stimulation (TMS) can be used to temporarily activate or inactivate parts of the human cortex, and infer function from these manipulations. 2) Magnetic resonance imaging (MRI), uses strong magnetic fields to image brain structure (structural MRI), connections between brain areas, and brain activation (functional MRI [fMRI]). 3) fMRI is based on activity induced changes in metabolic demand (neurons get hungry when active, they need sugar and oxygen). This changes blood flow to the active areas, and the oxygen supply agent (hemoglobin) can alter the magnetic field depending on how much oxygen it carries. 4) fMRI (in combination with other techniques) has revolutionized our understanding how function is localized in the human brain. 46 Spatial and temporal resolution of the prominent methods used in cognitive neuroscience. 47 Quiz Lecture 2 https://ncl.instructure.com/courses/42448/quizzes/42898 48 16  9/29/2022 Key points/questions today: What are mental processes, what are mental representations? How are these linked, how can they be studied? How can single cell activity in the brain be studied? What are the advantages and disadvantages? What insights into mental functions can Neurology yield? What are the difficulties using Neurological patients? What is the difference between single and double dissociations? What is TMS? What is fMRI? How has it revolutionized Cognitive Psychology? What are the benefits and limits of prominent methods used in neuroscience? 49 17