PSYCH50 Chapters 1-2
PSYCH50 Chapters 1-2 PSYCH 50
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This 7 page Class Notes was uploaded by Emily Wu on Thursday January 21, 2016. The Class Notes belongs to PSYCH 50 at Stanford University taught by Justin Gardner in Winter 2016. Since its upload, it has received 233 views. For similar materials see Intro to Cognitive Neuroscience in Psychlogy at Stanford University.
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Date Created: 01/21/16
Emily Wu email@example.com Chapter 1: Cognitive Neuroscience: Definitions, Themes, and Approaches Cognition Cognition: set of processes that allow humans to ultimately generate thoughts and actions that help reach desired goals ● many aspects of cognition occur subconsciously as reflex or automatically in the background of current processing Natural philosophy and early psychology ● 19th century scientists addressed cognition through behavioral observation and experiments Behaviorism ● behaviorism: emphasizes controlled experiments, objective external stimuli, and measurable behavior ● dominated early 20th century because of dissatisfaction with lack of systematic processes for studying cognition ● grounded psychology in objective experimental approach ● behaviorists: Watson and Skinner (reinforcement, learning, conditioning) ● faults: ignored mental states and cognitive functions besides learning Cognitive science ● the research of mental processesarose mid20th century ● Miller: people can represent about 7 items at a time in short term memory ○ memory is an active recoding of stimulus information, not a passive representation ● Chomsky: says behaviorism can’t explain mental phenomena ● cognitive models: describe underlying psychological processes and how sensory input turns into behavioral output Neuroscience ● research of how nervous systems are organized and their function ● Gall: phrenology, idea that cerebral cortex functions can be mapped by bumps on skull ○ gave rise to idea of localization of function: different parts of brain → different processes ● Santiago Ramon y Cajal: identified neurons as separate cells in brain ○ signals transmitted along neuronal axons by action potentials ○ neurotransmitters: chemicals released at terminal of axons across synapses, then bind to receptors on the next neuron ● Penfield: mapped somatosensory cortex by stimulating brain areas of patients + recording reported feeling Cognitive Neuroscience: The Neurobiological Approach to Cognition Cognitive neuroscience: intersects cognitive science and neuroscience ● finding neural correlates: mapping brain regions activated during psychological process ● understanding individual differences in cognitive abilities Methods: Convergence and Complementarity Convergence: combines results of multiple experimental models to illustrate one concept ● ex: using results from multiple experiments to link area activation to a specific process → consistent activation of middle temporal lobe in many motion experiments Complementarity: combining research methods to provide a full account of brain processes/image ● ex: use of fMRI, EEG, PET, TMS, etc. together Emily Wu firstname.lastname@example.org Chapter 2: The Methods of Cognitive Neuroscience ● approaches divided into two categories: a. study change in behavior when brain has been perturbed b. measure brain activity while cognitive tasks are being performed Brain Perturbations 1. Stroke, trauma, or disease: a. use of clinicalpathological correlationassociating area of brain lesion with changes in behavior and cognitive function i. cons: factors causing brain damage are not controlled by experimenter, diaschisis: damaged area may cause another area to lose functioning b. lesion studies in animals → can control region of brain damage, but training/assessment animals to do cognitive tasks is difficult 2. Pharmacological: a. psychoactive drugs interfere with neurotransmitter release and response b. correlational: study cognitive changes of chronic drug abusers c. experimental: administer drugs and record changes in functioning i. cons: lack of specificity of drug’s effects since drug affects entire brain d. agonists: increase neurotransmitter release or receptor sensitivity e. antagonists: decrease neurotransmitter release or receptor sensitivity 3. Intracranial brain stimulation: a. electrodes placed onto brain of animal/human during surgery b. moderate stimulation can activate neurons→ trigger behaviors c. strong stimulation can produce temporary but reversible “lesion” → disrupts neuron’s normal function 4. Extracranial brain stimulation: a. transcranial magnetic stimulation (TMS): strong rapidly changing magnetic field generated over scalp to produce rapidly changing electrical current in brain tissue → disrupts neuronal functioning i. repetitive TMS (rTMS): series of TMS pulses applied over several minutes ii. apply one TMS pulse at specific times → better temporal resolution b. cons: affects large area and limits specificity, delivered only to superficial brain areas, uncomfortable 5. Optogenetics: a. insert genetic material to create lightsensitive ion channels b. ion channels open and close in response to light of specific wavelength c. activate/inactivate neurons by opening/closing the ion channels and affecting their action potentials → change functioning of animal Measuring Neural Activity during Cognitive Processing 1. Direct electrophysiological recording a. measures action potentials produced by a single neuron (“spiking”) b. places electrodes extracellularly or intracellularly onto neuron c. data analyzed in two ways: i. peristimulus time histogram: plots neuronal firing pattern against time in response to one stimulus that is repeatedly producedeach iteration is a trial ii. tuning curves: stimulus is presented in varying dimensions, neuronal response intensity is plotted → result is a curve illustrating which variation of the stimulus elicited strongest response 2. Electroencephalography (EEG) a. measures electrical brain waves with surface electrodes b. measures dendritic field potentials: fluctuations in charge along neuron’s dendrites when neuron receives synaptic input c. local field potentials: a kind of dendritic field potential, but fluctuations have slower frequency 3. Eventrelated potentials (ERPs) a. small voltage fluctuations in an EEG recording triggered by sensory/cognitive events b. smaller than EEG data, so they must be averaged across trials to extract from background “noise” of raw EEG data 4. Magnetoencephalography (MEG) a. magnetic version of EEG b. eventrelated magneticfield responses (ERFs) extracted from MEG same way as ERPs c. measures magnetic fields produced by the depolarization and current flow of dendrites, rather than voltage fluctuations d. sensitive to activity in sulci, insensitive to gyri 5. Positron emission tomography imaging (PET) a. increased neural activity=increased blood flow to area b. unstable isotopes injected into bloodstream and migrate towards more metabolically active areas of brain c. decay of isotope emits positron → positron collides with electron → emits two gamma rays traveling in opposite direction → gamma ray detectors around subject’s head→ creates image of brain activity d. lower spatial resolution, no temporal resolution e. requires blocked design: measure brain activity over extended period of time as subject does task, then compare to activity measured over period of time when subject is not doing task 6. Functional magnetic resonance imaging (fMRI) a. oxyhemoglobin and deoxyhemoglobin have different magnetic resonance signals b. active brain areas use more oxygen → microvasculature increases blood flow to area, carrying oxyhemoglobin → deoxyhemoglobin concentration decreases → detection of blood oxygenation leveldependent (BOLD) signal: magnetic resonance signal changes c. has enough temporal resolution for eventrelated design: measuring activity while stimulus is presented → can link behavioral measures to detected neural responses 7. Optical brain imaging: a. active brain tissue transmits/reflects light differently than inactive tissue b. eventrelated optical signals (EROS): amount of light transmitted vs scattered varies based on electrically active tissue → light shined into brain → measure intensity of reflected light c. high temporal resolution, low spatial resolution Using fMRI to analyze activation patterns within a brain area ● standard fMRI analysis obscures intervoxel differences ● voxel: a value on a grid in 3D space, like a pixel on a bitmap ● to address this problem: pattern classification ○ multivoxel pattern analysis (MVPA): looks at activation patterns across different voxels due to a stimulus rather than activation of a large brain area ○ ex: occipital cortex is responsive to seeing objects, but specific voxels may respond differently to images of a car vs. image of a house ● fMRI adaptation: a type of repetition suppression technique ○ areas of brain respond less and less after being shown a repeated stimulus ○ can assess whether same brain area responds to different stimuli ○ ex: if shown a picture of table repeatedly, occipital lobe activates then responds less → if shown a drawing of table or table at different angle, occipital lobe has suppressed response → suggests that occipital lobe processes both stimuli as same/similar → processes object’s abstract properties rather than sensory details Using fMRI to examine activity relationships between brain areas ● brain areas don’t function in isolation → information flows through fiber tracts: axons bundled together between brain areas ● functional connectivity: how activity of one brain area varies with activity of another area ○ example: coactivation → two brain regions respond similarly to experimental stimuli ○ restingstate connectivity: identifies regions that vary in conjunction when participant lies in MRI scanner but doesn’t do any tasks → measures spontaneous activity in brain rather than activity in response to specific stimuli ○ areas with functional connectivity tend to show restingstate connectivity Method Measures measure coverage spatial temporal invasive? participants activity resolution resolution relationship impairment damage area of the limited to little to none invasive animals or Lesions in removes damage size of patients with functioning neural activity lesion stroke, after brain in region trauma, etc. damage change in pulse superficial limited to some when noninvasive healthy TMS functioning temporarily brain areas areas pulse given humans (may after given stimulates or affected by in one shot cause pulses disrupts neural the pulses rather than seizures in activity repeatedly some) action neuron fires in single high high invasive animals singleunit recording potentials response to neuron produced by specific single stimulus neuron dendritic dendrite mainly near coarse/probl good noninvasive humans EEG field voltage surface of ematic potentials fluctuates brain when neuron receives input gamma rays isotopes whole brain good (3D) none noninvasive humans PET emitted by migrate decaying towards brain isotopes area of high injected into activity bloodstream fMRI BOLD areas with high whole brain very good better than noninvasive humans signals activity require PET, but still more blood, limited (a few oxyhemoglobin seconds) increases optical imaging intensity of active areas whole brain high better than invasive animals (hemodynamic) reflected reflect light fMRI, but still light differently than limited inactive (hundreds of milliseconds) optogenetics change in light sensitive selective limited to high invasive animals functioning ion channels neural the neural after open/close circuits circuits procedure when chosen responding to light, affects action potentials and neural activity
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