In Exercises 6770, determine whether the statement is true or false. Justify your answer. In a system of linear equations, when the determinant ofthe coefficient matrix is zero, the system has nosolution.
Week 6: Comparative Anatomy ● occipital lo mostly important for sight ● temporal lobe responsible for processing sensory information, includes fusiform gyrus (for face recognition), wernicke’s area (for speech comprehension, primary auditory cortex; medial temporal lobes play important role in encoding episodic memories ● parietal lo includes the somatosensory cortex; lesion in right parietal cortex results in hemineglect syndrome (person doesn’t process stimuli in left visual field) ● frontal lo includes the primary motor cortex, involved in executive functions like decision making, planning, inhibition of unwanted behavior ● gyrusthe ridges formed from the folding of the cortex ● sulcusthe valleys formed from the folds ● axial, coronal, sagittal refer to different kinds of cuts that are made to study the anatomy of the brain medial:towards the middle lateral towards the side ● gray matter:regions of the brain that are rich in neuronal cell bodies; includes nuclei of brain, cerebral and cerebellar cortices ● white matter: large axon tracts in the brain and spinal cord, often myelinated ● gyrification inde a way to quantitatively measure the folding of the brain cortex across species; takes the length of the contour along all the gyri/folds and divides it by the length of the actual exposed surface of the cortex ○ GI = complete contour/outer exposed contour ○ a higher GI is associated with more folding of the cortex, and generally indicates higher intelligence (humans have a higher GI than sheep, for example) ● brainstem: sits atop the upper end of the spinal cord and includes the midbrain, pons, and medulla; manages reflexive behavior like breathing rate, consciousness, and heart rate; also involved with reward system (covered in the next section) ● hippocampus: important for retention and encoding of episodic memory, but not so much semantic memory ● medial temporal lobes: damage to this area generally results in amnesia that impairs declarative memory, but not so much working memory ● amygdala: part of limbic system that is important for the processing of emotion; also important for acquisition and expression of conditioned fear ● synaptic pruning: the loss or rearrangement of synaptic connections that we don’t use/are no longer necessary ● whisker barrel cortex the primary somatosensory cortex of rodents show overrepresentation for their whiskers → each whisker has a module of cortex called a whisker barrel that is disproportionately large compared to other cortex areas ○ demonstrates the specialization of the brain to the behavior of different species ○ for example, humans have an overrepresentation of fingers in the primary motor cortex Week 7: Reinforcement Learning/Emotion ● neuroeconomics: the use of neuroscience to resolve issues in economics ○ developed because rational choice models did not accurately predict what people actuall choose, since people don’t always make rational choices ● dopamine: neurotransmitter involved in learning and reward evaluation ● dopaminergic pathways: ○ mesolimbic pathway: VTA project to nucleus accumbens in the basal ganglia → amygdala, hippocampus, other cortical regions ○ nigrostriatal pathway: substantia nigra projects to dorsal striatum of basal ganglia ● reward prediction erro R Vpredicted = reward prediction error ○ gets minimized over time ● RescorlaWagner learning: ○ Vpredicted = Vpredicted + α( R Vpredicted) ○ first Vpredicted is the value being updated; second and third Vpredicted are the initial prediction of the values ○ α= learning rate ○ R = reward value ● temporal difference learninsuccessive states of the world are correlated over time, so our predictions about those states also change and correlate over time ○ reward prediction error guides behavior through temporal difference learning ● autonomic nervous system: responsible for unconscious bodily functions like breathing, digestion, and regulating heart beat ○ sympathetic: prepares the body for fight or flight; release of adrenaline, increases heart rate, perspiration, attention ○ parasympathetic: counters the effects of sympathetic nervous system after the body becomes aroused ● skin conductance response: measured by placing electrodes on the skin surface to measure the electrical activity in response to emotions ○ sweat glands are activated more during emotional arousal → increased electrical conductance ● nucleus accumbens: part of the basal ganglia, VTA projects to nucleus accumbens in the mesolimbic pathway ● ventral tegmental area (VTA dopamine neurons in the midbrain that project to nucleus accumbens ● substantia nigr dopamine neurons in the midbrain that project to the caudate and putamen of the basal ganglia Week 8: Memory ● double dissociatio using experimental behavior tests to dissociate different brain areas and functions ● in the context of tweather prediction task: ○ Weather prediction task → 4 cards predicted rain/shine with a certain probability ○ involves working memory/skill learning ○ Accuracy in skill learning for control population increases over number of trials ○ Amnesiacs (damage to MTL): accuracy improves over time ○ Parkinson’s disease (damage to basal ganglia): accuracy doesn’t improve over time ● in context of tpairedassociation task: ○ paired association task→ certain pairings of cards were associated with rain or shine ○ involves episodic memory ○ Control and parkinson’s populations have about same accuracies ○ Amnesiacs more impaired in accuracy ● from this double dissociation, one can conclude that since damage to basal ganglia → impaired skill learning, and damage to MTL → impaired episodic memory, the basal ganglia and MTL have different functions for memory that are independent of each other ● classical conditioning: ○ unconditioned response (UCR): an innate response to a stimulus ○ unconditioned stimulus (UCS): the stimulus that elicits the UCR ○ conditioned stimulus (CS): an unrelated stimulus paired with the UCS ○ conditioned response (CR): the reflex that happens with presentation of the CS ○ ex: dog salivates (UCR) at sight of food (UCS) → pair bell tone with food → dog salivates (CR) when it hears the bell tone (CS) ● operant conditionin increasing or decreasing a behavior by giving rewards or punishments ● fear conditioninrats are conditioned with a tone (CS) that precedes a mild foot shock (US) → after many trials, rats show change in physiology and react in fear when the tone is presented alone (CS) → show increased blood pressure, heart rate and breathing rates, engagement of sympathetic fight or flight response ● extinctio: removal of unconditioned stimulus when subject repeatedly performs conditioned response → conditioned response decreases in absence of unconditioned stimulus ● contextual fear conditioniwhen a fear response is also elicited by features of the environment, such as parts of the testing chamber where the conditioning took place, as opposed to fear response being elicited by a cue/conditioned stimulus (this is cued fear conditioning) ● synaptic consolidatigrowth of new synaptic connections or restructuring of existing ones in the first few hours of learning ● system consolidatio gradual process of reorganization of structures in the brain pertaining to memory after learning, slower process than synaptic consolidation ● standard consolidation theoduring encoding of a memory, details are stored in cortical areas involved in processing different aspects of the event (auditory, visual, etc.) and summary of the event is stored in hippocampus → during storage/consolidation, traces of the memory are stabilized → during retrieval of an event, hippocampus receives a cue that activates the various cortical traces that stored the parts of that event ● multiple trace theo distinguishes between episodic and semantic memories ○ episodic memories are always dependent on the hippocampus, and each time a memory is reactivated, it leaves a new memory trace in the hippocampus → older memories then have more traces stored in hippocampus and are harder to erase when hippocampus is partially damaged ○ semantic memories are gradually stored in the cortex independently from the hippocampus ● pattern separation: ○ we encode representations very differently in our brains even though they’re visually similar ○ the different representations are encoded by different patterns of brain activity so that they can be encoded as separate memories ● pattern completio using a clue/piece of evidence to trigger a memory of a complete pattern ○ CA3 region has a recurrent collateral mechanism → input causes a pattern that’s associated with a memory ○ if the input is incomplete, then the input associates back to itself and activates other connections at the same time, completing the pattern ● subsequent memory paradigm: can be used to distinguish between brain activity for encoding vs. retrieval of memories ○ subjects study a series of items while brain activity is recorded ○ subjects perform encoding trials, requiring them to remember some of the studied items and forgetting others ○ encoding trials are then labeled as subsequently remembered or subsequently forgotten depending on how the subjects did ○ brain activity during these two trials are then compared using data from eventrelated potentials brain structures important for memory: ● prefrontal corteworking memory ● medial temporal lob involved in episodic memory ● hippocampus: integrates memory traces from cortices when encoding memory, then activates all traces when retrieving memory ● basal gangli important for skill learning ● amygdala: important in the acquisition and expression of fear conditioning ● cerebellum:error correction and learning ● sensory cortexperceptual priming Week 9: Synapse ● synapse:the space between neurons ● axon termina the end of the axon ● presynaptic/postsynap the neuron before vs after the synapse ● electrical synap current flows from presynaptic neuron into postsynaptic neuron ○ pre and post synaptic neurons are linkap junction ○ gap junction contains specially aligned ion channels that allow ions to pass through ○ transmission across gap junction can go either way and is really fast ● chemical synapse communication between neurons occurs through neurotransmitters/chemicals ○ space between pre and postsynaptic neurons is cynaptic cl space is much larger than a gap junction ○ presynaptic neuron haesicle small spheres, membranebounded, contains neurotransmitters ● voltage gated ion channpens/closes based on electrical current ● ligand gated ion channpens/closes depending on chemical that binds to it ● ionotropic receptolinked directly to ion channels ○ contains an extracellular site that binds neurotransmitters, and membranespanning domain that creates an ion channel ○ combines neurotransmitter binding and ion channel functions ○ made up of several units ○ create rapid postsynaptic potentials ● metabotropic receptoactivate ion channels by activation of intermediate called Gprotein ○ contains extracellular site that binds neurotransmitters and intracellular site that binds G proteins ○ binding of neurotransmitter → binding and activation of G protein → G protein interacts directly with ion channels or other proteins ○ consist of single units ○ create slower postsynaptic potentials ● Ca2+: ○ in vesicle release: calcium ion voltage gated channels open when action potential reaches axon terminal → influx of Ca2+ into the presynaptic neuron causes vesicles to fuse with neuronal membrane and empty neurotransmitters across the synaptic cleft ○ in LTP: glutamate receptor that is blocked by Mg2+ when the postsynaptic cell is resting → when postsynaptic cell is depolarized, Mg2+ is removed and allows Ca2+ to enter the cell, triggering LTP ● neurotransmitter reuptak neurotransmitters that was emptied into the synapse by the presynaptic cell get taken back into the presynaptic cell ● excitator increase likelihood of action potential firing in postsynaptic cell ● inhibitor decrease likelihood of action potential firing ● glutamate: excitatory neurotransmitter that is important for brain function; nearly all excitatory neurons activated by glutamate ○ its precursor is glutamine ● dopamine: reward evaluation and learning ● serotoninmood regulation, also mediates gut regulation ○ precursor is tryptophan ○ binds to 5HT receptor ● long term potentiatia longlasting increase in neural transmission between two neurons, results in strengthening of synapses ● NMDA receptor: glutamate receptor that is blocked by Mg2+ when the postsynaptic cell is resting → when postsynaptic cell is depolarized, Mg2+ is removed and allows Ca2+ to enter the cell ○ LTP is triggered when the presynaptic neuron fires to release glutamate while the postsynaptic cell is depolarized at the same time → strengthens the synapse between the neurons and in turn changes the gene expression of the cell → increases the number of glutamate receptors on the postsynaptNMDA ll ( upregulation) Week 10: ● autism spectrum disordeneurodevelopmental disorder characterized by deficits in communication, social interactions, repetitive stereotyped behaviors ○ different from other disorders by having social deficits as core symptom ○ DSM criteria: impairment using nonverbal behavior, failure to develop peer relationships, failure to spontaneously share interests with others, lack of social/emotional reciprocity ○ difficulty processing faces, emotional expressions, and biological motion ○ reduced activation in fusiform gyrus and amygdala when viewing faces ○ difficulty integrating parts into wholes/synthesizing information ○ difficulty following gaze/using gaze to infer other people’s intentions ○ tend to analyze problems by applying rigid rules ● pathway for face processinpathway begins in occipital lobe upon seeing a face ○ divided into ventral and dorsal pathways that process in parallel ○ ventral: processes invariant aspects of face, discriminates faces from other objects and other faces, includes fusiform face area → sent to anterior temporal lobe, where face is linked with semantic/episodic knowledge about the person ○ pathway important for person recognition ○ dorsal: processes changeable aspects of faces like perception of eye gaze and expressions, superior temporal sulcus → limbic system (emotion processing), auditory complex (speech perception), and intraparietal sulcus (spatial attention processing) ○ ventral pathway: occipital lobe → fusiform face area → anterior temporal lobe ○ dorsal pathway: occipital lobe → superior temporal sulcus → limbic system, auditory complex, intraparietal sulcus ● mirror neurons: discovered in macaque monkeys in inferior prefrontal gyrus ○ increase activity when grasping action is performed and also when grasping action of another person/animal is viewed ○ may be important in understanding empathy, theory of mind, and language acquisition ○ evidence for mirror neurons in humans is suggestive but do not have same anatomical features as those found in monkeys ● theory of mind:inferring the mental states of others, attributing actions of others to their beliefs, goals, desires, feelings ● join attentio directing your attention to something that is cued by someone else ● savant syndrome: people who have mental disabilities such as autism but possess abnormally high capabilities in specific areas ventral medial prefrontal cortreceives and regulates sensory input temporoparietal junction border between parietal and temporal lobes; contributes to outofbody experiences fusiform face area face recognition and person identification superior temporal sulcus processes changeable aspects of faces like eye gaze and expressions, projects to the limbic system during face perception amygdala: activity in this area related to implicit racial biases