Memory and Cognition PSY 324 Topic 2: Cognition and the Brain Dr. Ellen Campana Arizona State...

Memory and Memory and CognitionCognition

PSY 324PSY 324

Topic 2: Cognition and the Topic 2: Cognition and the BrainBrain

Dr. Ellen CampanaDr. Ellen Campana

Arizona State UniversityArizona State University

A BrainA Brain

Gray & White Gray & White MatterMatter

Solid tissueSolid tissue Made up of Made up of

neuronsneurons Golgi Golgi showed by showed by

staining slices staining slices with dyewith dye

NeuronsNeurons

Similarities with other cells of the bodySimilarities with other cells of the body Have a Have a nucleusnucleus containing DNA containing DNA Surrounded by a Surrounded by a cell membranecell membrane Contain mitochondria and other organellesContain mitochondria and other organelles Do basic cell stuff (protein synthesis, Do basic cell stuff (protein synthesis,

energy production)energy production) Unique characteristicsUnique characteristics

Do not reproduceDo not reproduce Structure, function, chemicals (details to Structure, function, chemicals (details to

come)come)

Structure of a NeuronStructure of a Neuron

Varieties of neuronsVarieties of neurons

Function = transmit information to Function = transmit information to other cellsother cells Sensory / Afferent neuronsSensory / Afferent neurons: info : info

TOWARDTOWARD CNS CNS Motor / Efferent neurons: Motor / Efferent neurons: info info AWAY AWAY

fromfrom CNS CNS Interneurons: Interneurons: info to other neurons in info to other neurons in

the CNSthe CNS

Info Transmission: Info Transmission: Simple StorySimple Story

Neurons are Neurons are transducerstransducers – convert – convert environmental energy to electrical energy environmental energy to electrical energy (starting with (starting with receptorsreceptors))

Energy is Energy is propagatedpropagated from the from the dendritesdendrites into into the the cell body.cell body.

Energy is propagated to the end of the axon. Energy is propagated to the end of the axon. When it goes above a When it goes above a thresholdthreshold, it triggers the , it triggers the release of release of neurotransmittersneurotransmitters into the into the synapsesynapse

The neurotransmitters in the synapse trigger the The neurotransmitters in the synapse trigger the same process (or a different one) in the next cellsame process (or a different one) in the next cell

SynapsesSynapses

Info Transmission: Info Transmission: Deeper StoryDeeper Story

Background concepts from physicsBackground concepts from physics Matter composed of molecules (always Matter composed of molecules (always

moving)moving) Molecules can have +/- chargeMolecules can have +/- charge Like charges repel, opposite charges Like charges repel, opposite charges

attractattract

+ +- -+ -


Each neuron has a Each neuron has a resting resting potentialpotential, the voltage difference , the voltage difference across the cell membrane, caused by across the cell membrane, caused by the chemicals inside/outside the cell the chemicals inside/outside the cell when the cell is not firingwhen the cell is not firing

- --

-- -

--

--

++ +

+ ++ +

+

++ +

+ ++ +

+


Axon lined with Axon lined with ion channelsion channels (sodium channels, potassium (sodium channels, potassium channels) that open and close during channels) that open and close during an an action potentialaction potential to to propagatepropagate the signalthe signal Depolarization phase: Depolarization phase: Sodium (Na+) Sodium (Na+)

ChannelsChannels Repolarization phase: Repolarization phase: Potassium (K+) Potassium (K+)

ChannelsChannels

Depolarization PhaseDepolarization Phase

Depolarization + Depolarization + RepolarizationRepolarization


Action potentialAction potential moves down the moves down the axon, as gates open and close in axon, as gates open and close in sequencesequence

SynapsesSynapses

Action PotentialAction Potential reaches the end reaches the end of the axon, triggering release of of the axon, triggering release of neurotransmittersneurotransmitters

•Excitatory neurotransmitters increase firing rate in next neuron•Inhibitory neurotransmitters decrease firing rate in next neuron

•NOTE: Other neurotransmitters do other things (less well understood, less relevant to cognition, especially to models we will talk about)

Method: Single-Cell Method: Single-Cell RecordingRecording

It is possible to record activity of a single It is possible to record activity of a single cellcell

Tiny wires (called Tiny wires (called microelectrodesmicroelectrodes) stuck ) stuck into into axonaxon, attached to , attached to oscilloscopeoscilloscope for data for data displaydisplay

Time is a factorTime is a factor De/Repolarization cycle = 1/1000 S or 1 msDe/Repolarization cycle = 1/1000 S or 1 ms Activities of cognition take at least 100ms – at Activities of cognition take at least 100ms – at

that resolution action potentials show up as that resolution action potentials show up as spikesspikes

Often most useful to talk about Often most useful to talk about firing rate firing rate

Method: Single-Cell Method: Single-Cell RecordingRecording

Pictures of “spikes” – Pictures of “spikes” – http://viperlib.york.ac.uk/ , keyword , keyword

single cell recordingsingle cell recording Video clip from Video clip from Hubel & WeiselHubel & Weisel

(they got the (they got the 1981 Nobel Prize1981 Nobel Prize in in physiology and medicine for this physiology and medicine for this work)work) http://viperlib.york.ac.uk/ , keyword , keyword

single-cell recordingsingle-cell recording

History of Single-Cell History of Single-Cell RecordingRecording

Participants in experiments:Participants in experiments: 1880s – People injured by accident with 1880s – People injured by accident with

exposed brains, also patients with epilepsyexposed brains, also patients with epilepsy 1950s – Fully anesthetized animals (cats, 1950s – Fully anesthetized animals (cats,

squirrels, monkeys, apes)squirrels, monkeys, apes) 1980s – Awake, active monkeys and apes1980s – Awake, active monkeys and apes

Invasive, destructive procedureInvasive, destructive procedure Data: there is a cell in the [animal] that Data: there is a cell in the [animal] that

increases firing under [conditions]increases firing under [conditions]

Value of Single-Cell Value of Single-Cell RecordingRecording

By itself, the data doesn’t tell us muchBy itself, the data doesn’t tell us much Can find cells that do almost anythingCan find cells that do almost anything

The value of single-cell recording for The value of single-cell recording for understanding human cognition depends understanding human cognition depends on:on: Functional organizationFunctional organization of the brain of the brain Consistencies of organization within speciesConsistencies of organization within species Meaningful mapping from animal models to Meaningful mapping from animal models to

organization of human brainorganization of human brain Fortunately, much evidence that these Fortunately, much evidence that these

existexist

Clarification from last Clarification from last timetime

Question came up about diffusion Question came up about diffusion and connection to neuron behaviorand connection to neuron behavior


Background concepts from physicsBackground concepts from physics Matter composed of molecules (always Matter composed of molecules (always

moving)moving) Molecules can have +/- chargeMolecules can have +/- charge Like charges repel, opposite charges Like charges repel, opposite charges

attractattract

+ +- -+ -


Background concepts from physicsBackground concepts from physics Matter composed of molecules (always moving)Matter composed of molecules (always moving) Molecules can have +/- chargeMolecules can have +/- charge Like charges repel, opposite charges attractLike charges repel, opposite charges attract

Cell membrane maintains an imbalance Cell membrane maintains an imbalance At rest, negative inside and positive outside At rest, negative inside and positive outside

(pumps maintain)(pumps maintain) Ion channels open / close quicklyIon channels open / close quickly Particles rush in / out (like a hole in a boat)Particles rush in / out (like a hole in a boat) Sodium and Potassium are +, but other chemicals Sodium and Potassium are +, but other chemicals

create the negativity inside the axon at rest create the negativity inside the axon at rest Focus on Sodium and Potassium because of the Focus on Sodium and Potassium because of the

gatesgates


- --

-- -

--

--

++ +

+ ++ +

+

++ +

+ ++ +

+

AxonCell membrane (imbalance)Diffusion and charge drive the process – cells rush in/outThere are mechanical pumps but they just restore resting potential at the end


Things to noteThings to note All action potentials are the same size, All action potentials are the same size,

in terms of voltage (all-or-nothing in terms of voltage (all-or-nothing principle)principle)

Most useful to think of them as on / off, Most useful to think of them as on / off, or to think about firing rates (spikes per or to think about firing rates (spikes per second)second) These are from a specific

study. Neuron A responds when the

stimulus is ON. Neuron B responds when the

stimulus is OFF. Neuron C responds to changes in

the stimulus.

Why study neurons?Why study neurons?

Everything we see, hear, do, smell, Everything we see, hear, do, smell, remember, taste, touch, pay attention remember, taste, touch, pay attention to, and think about is to, and think about is represented represented physiologicallyphysiologically by neurons firingby neurons firing All sensations, perceptions and thoughts All sensations, perceptions and thoughts

are neural activationare neural activation All of our actions arise from neural signalsAll of our actions arise from neural signals

Study of cognition is about both Study of cognition is about both physiologicaphysiological and l and functional modelsfunctional models Increasingly uses brain imaging and Increasingly uses brain imaging and

neuroscience methods (later today)neuroscience methods (later today)

Brain OrganizationBrain Organization

Hierarchical StructureHierarchical Structure Smallest unit: NeuronSmallest unit: Neuron Neurons form Circuits (many levels)Neurons form Circuits (many levels)

Convergence, Inhibition, ExcitationConvergence, Inhibition, Excitation Related circuits contribute to localized Related circuits contribute to localized

functionfunction Brain areas for different functionsBrain areas for different functions Hemispheric specializationHemispheric specialization

Neurons as part of Neurons as part of circuitscircuits

Neural processingNeural processing occurs when neurons occurs when neurons synapse together to form a synapse together to form a neural circuitneural circuit ConvergenceConvergence Interaction ofInteraction of excitation excitation and and inhibitioninhibition

Hubel & WeiselHubel & Weisel Single-cell recording of Single-cell recording of feature feature

detectorsdetectors Simple neuronsSimple neurons (from the video last (from the video last

time)time) Orientation (thickness, location of line)Orientation (thickness, location of line)

Complex neuronsComplex neurons Orientation, direction of motionOrientation, direction of motion

End-stoppedEnd-stopped Length, direction of motionLength, direction of motion

Feature DetectorsFeature Detectors

Lines (shapes and orientations)Lines (shapes and orientations) Directed MotionDirected Motion Complex StimuliComplex Stimuli

Geometrical figuresGeometrical figures Common objects in the environment Common objects in the environment

(houses, man-made objects, birds)(houses, man-made objects, birds) FacesFaces

Depend on Depend on selectivityselectivity – neurons – neurons firing at some times and not at othersfiring at some times and not at others

Neural Codes in Daily Neural Codes in Daily LifeLife

Consider the case of recognizing the Consider the case of recognizing the face of a specific person – how could face of a specific person – how could that happen?that happen?

Hypothesis 1: Hypothesis 1: specificity tuningspecificity tuning – a – a particular neuron could selectively fire particular neuron could selectively fire when you see that personwhen you see that person

Specificity CodingSpecificity Coding Difficulties with Specificity Coding HypothesisDifficulties with Specificity Coding Hypothesis

Too many different faces, concepts, etc. to have a Too many different faces, concepts, etc. to have a neuron for each oneneuron for each one

Depends on experience – would have to learn each Depends on experience – would have to learn each face (because neurons don’t reproduce)face (because neurons don’t reproduce)

Neurons selective for faces are active for many Neurons selective for faces are active for many different facesdifferent faces

Related idea: Related idea: Grandmother cellGrandmother cell (coined by (coined by LettvinLettvin)) Cell responds to image of a grandmother, general Cell responds to image of a grandmother, general

concept of grandmothers, your own grandmotherconcept of grandmothers, your own grandmother Some evidence that these might exist in Some evidence that these might exist in

Hippocampus – associated with memory storage, Hippocampus – associated with memory storage, not visionnot vision

For recognition (and many other types of For recognition (and many other types of cognition), specificity coding is not enoughcognition), specificity coding is not enough

Neural Codes in Daily Neural Codes in Daily LifeLife

Hypothesis 2: Hypothesis 2: Distibuted CodingDistibuted Coding – – code for a specific face is distributed code for a specific face is distributed across a set of neuronsacross a set of neurons

Distributed CodingDistributed Coding

AdvantagesAdvantages Efficient -- firing of fewer neurons can Efficient -- firing of fewer neurons can

represent many more different stimulirepresent many more different stimuli Similar items can have similar neural Similar items can have similar neural

codescodes Helps with learning Helps with learning

Graceful degradationGraceful degradation -- if one or two -- if one or two neurons do not fire, it is still possible to neurons do not fire, it is still possible to recognize a facerecognize a face

Reconciling types of Reconciling types of codingcoding

Evidence for Specificity Coding Evidence for Specificity Coding Feature detectorsFeature detectors Concept cells in hippocampus (memory area)Concept cells in hippocampus (memory area)

Argument for Distributed Coding in Argument for Distributed Coding in recognitionrecognition Clear theoretical advantages in recognitionClear theoretical advantages in recognition Will see a lot of evidence laterWill see a lot of evidence later

Both are happening in the brain – in different Both are happening in the brain – in different areas at the same time (areas at the same time (parallel parallel processingprocessing)) Pattern across (+ interaction btwn) Pattern across (+ interaction btwn)

areas=cognitionareas=cognition

The Whole BrainThe Whole Brain

Localization of functionLocalization of function - Different - Different parts of the brain serve different parts of the brain serve different functionsfunctions

Many, many ways to divide the brainMany, many ways to divide the brain Like an onion, many layersLike an onion, many layers Like a fractal, the closer you look the Like a fractal, the closer you look the

more complex it seems more complex it seems Descriptions may seem contradictory Descriptions may seem contradictory

and/or overlapping because of thisand/or overlapping because of this

Cerebral CortexCerebral Cortex Most important for CognitionMost important for Cognition

Cerebral CortexCerebral Cortex

Temporal Lobe Temporal Lobe LanguageLanguage MemoryMemory HearingHearing Perceiving formsPerceiving forms

Occipital LobeOccipital Lobe Visual information (early processing) – Visual information (early processing) –

feature detectorsfeature detectors

Cerebral CortexCerebral Cortex Parietal LobeParietal Lobe

TouchTouch VisionVision AttentionAttention

Frontal Lobe Frontal Lobe Proportionately larger in humans than Proportionately larger in humans than

in other speciesin other species LanguageLanguage ThoughtThought MemoryMemory Motor functioningMotor functioning

Subcortical StructuresSubcortical Structures

Subcortical StructuresSubcortical Structures

HippocampusHippocampus Forming memoriesForming memories

AmygdalaAmygdala Emotions, emotional memoriesEmotions, emotional memories

ThalamusThalamus Processing sensory information (vision, Processing sensory information (vision,

hearing, touch)hearing, touch)

HemispheresHemispheres

Brain separated into sides (hemispheres)Brain separated into sides (hemispheres) Corpus CollosumCorpus Collosum connects them connects them

Structurally and Structurally and functionally very functionally very similarsimilar

LateralizationLateralization – – specific functions specific functions occurring in one occurring in one hemisphere or the hemisphere or the otherother

Note: Sperry studied “split-brain patients”, who had had their corpus collosum severed as a treatment for epilepsy. He shared Hubel & Weisel’s Nobel Prize for this work.

LateralizationLateralization

Vision of left part of the world Vision of left part of the world lateralized to the right side (opposite lateralized to the right side (opposite also true)also true)

Motor Control of left side of body Motor Control of left side of body lateralized to the right side (opposite lateralized to the right side (opposite also true)also true)

Touch on left side of body lateralized Touch on left side of body lateralized to the right side (opposite also true)to the right side (opposite also true)

LateralizationLateralization Are there “right-brained” and “left-Are there “right-brained” and “left-

brained” people?brained” people? Analytical/Logical processing (syntax of Analytical/Logical processing (syntax of

language) usually on the left side (not always)language) usually on the left side (not always) Analogy and Broad Thinking usually on the Analogy and Broad Thinking usually on the

right side (not always)right side (not always) Everyone has (and uses) bothEveryone has (and uses) both Patients who have had a Patients who have had a

hemispherectomyhemispherectomy Other side usually takes over missing Other side usually takes over missing

functionalityfunctionality Coglab “Brain Assymetry” Coglab “Brain Assymetry”

Localized FunctionLocalized Function

Parietal LobeParietal Lobe Sensory HomunculusSensory Homunculus (near the front, (near the front,

somatosensory cortexsomatosensory cortex)) Motor HomunculusMotor Homunculus (near the back, (near the back,

motor cortexmotor cortex))

These guys aren’t actually IN your brain, they’re representations of how much cortex area is devoted to different body parts

Sensory HomunculusSensory Homunculus

Each side of the brain has a

copy, which processes

touch from the other side

Localized FunctionLocalized Function

Parietal LobeParietal Lobe Sensory HomunculusSensory Homunculus (near the front, (near the front,

somatosensory cortexsomatosensory cortex)) Motor HomunculusMotor Homunculus (near the back, (near the back,

motor cortexmotor cortex)) Temporal LobeTemporal Lobe

Wernicke’s AreaWernicke’s Area – metaphor, meaning – metaphor, meaning in languagein language

Broca’s AreaBroca’s Area – logical structure of – logical structure of languagelanguage

Fusiform Face Area (FFA)Fusiform Face Area (FFA) – – specialized for faces (or is it things specialized for faces (or is it things we’re experts at recognizing???)we’re experts at recognizing???)

Researching Localized Researching Localized FunctionFunction

NeuropsychologyNeuropsychology – comparing – comparing patients with localized brain damagepatients with localized brain damage Single dissociationSingle dissociation– single patient has – single patient has

some things impaired, other things not some things impaired, other things not impairedimpaired

Single Dissociation: Single Dissociation: Phineas GagePhineas Gage

Construction Construction accident – 1848accident – 1848

Harlow (doctor) Harlow (doctor) wrote a lot about wrote a lot about his conditionhis condition Gage lived, could talk, act, and do Gage lived, could talk, act, and do

all “normal” activities, but suffered all “normal” activities, but suffered impairment of emotional, social, and impairment of emotional, social, and personal traitspersonal traits

Evidence for some separation of Evidence for some separation of language and social traits, etc. language and social traits, etc.

Researching Localized Researching Localized FunctionFunction

NeuropsychologyNeuropsychology – comparing – comparing patients with localized brain damagepatients with localized brain damage Single dissociationSingle dissociation – single patient has – single patient has

some things impaired, other things not some things impaired, other things not impairedimpaired

Alice: Short-Term Memory OK, Long-Term Alice: Short-Term Memory OK, Long-Term Memory impaired (like in Memento)Memory impaired (like in Memento)

Double dissociationDouble dissociation -- two (or more) -- two (or more) patients show opposite single impairmentspatients show opposite single impairments

Bert: Long-Term Memory OK, Short-Term Bert: Long-Term Memory OK, Short-Term Memory impairedMemory impaired

Double DissociationDouble Dissociation

Short-term Short-term memorymemory

Long-term Long-term memorymemory

Alice Alice (temporal (temporal lobe damage)lobe damage)

OKOK ImpairedImpaired

Bert (frontal Bert (frontal lobe damagelobe damage

ImpairedImpaired OKOK

Double DissociationDouble Dissociation

Naming Naming Living ThingsLiving Things

Naming Naming Nonliving Nonliving ThingsThings

Group 1 Group 1

(damage to (damage to area 1)area 1)

OKOK ImpairedImpaired

Group 2Group 2

(damage to (damage to area 2)area 2)

ImpairedImpaired OKOK

What can we conclude?What can we conclude?

Double dissociationDouble dissociation Two functions involve different mechanismsTwo functions involve different mechanisms Two functions involve different brain areasTwo functions involve different brain areas Mechanisms Mechanisms areare independent independent

Single dissociationSingle dissociation Two functions involve different mechanismsTwo functions involve different mechanisms Two functions involve different brain areasTwo functions involve different brain areas Mechanisms Mechanisms may not bemay not be independent independent

Limitations of Limitations of NeuropsychologyNeuropsychology

At least for human processing, brain At least for human processing, brain damage comes about from natural means damage comes about from natural means (accident, etc.)(accident, etc.) Members of groups rarely have exactly the Members of groups rarely have exactly the

same damage (location or extent)same damage (location or extent) No record of processing or brain organization No record of processing or brain organization

before the damagebefore the damage Difficult to assess all possible types of Difficult to assess all possible types of

functional impairment functional impairment Damage may cause reorganization Damage may cause reorganization

((plasticityplasticity))

Imaging MethodsImaging Methods EEGEEG- Electrodes on outside of head continuously - Electrodes on outside of head continuously

measure electrical activitymeasure electrical activity PETPET- Radioactive dye injected, accumulates in - Radioactive dye injected, accumulates in

different regions over time and can be read by a different regions over time and can be read by a scanner. Essentially measures metabolism of neuronsscanner. Essentially measures metabolism of neurons

fMRIfMRI- Brief magnetic pulses used to give a snapshot - Brief magnetic pulses used to give a snapshot of ratio of oxygenated to deoxygenated blood of ratio of oxygenated to deoxygenated blood (metabolism)(metabolism)

TMSTMS- New measure. Magnetic field can disable - New measure. Magnetic field can disable specific portions of the brain for a short time, specific portions of the brain for a short time, simulating damage.simulating damage.

Temporal resolutionTemporal resolution: Detail with respect to time: Detail with respect to time Spatial ResolutionSpatial Resolution: Detail with respect to physiology: Detail with respect to physiology

Image from an

fMRI scanImage from a

PET scan

Imaging MethodsImaging Methods

Spatial Spatial ResolutionResolution

Temporal Temporal ResolutionResolution

EEGEEG PoorPoor GoodGood

PETPET ExcellentExcellent PoorPoor

fMRIfMRI GoodGood GoodGood

TMSTMS GoodGood GoodGood

Subtraction TechniqueSubtraction Technique

Used for fMRI studiesUsed for fMRI studies Method similar to Method similar to

Donder’s studyDonder’s study Compared two Compared two

situations that situations that included different included different cognitive processescognitive processes Data = blood glucose Data = blood glucose

levellevel Relative measureRelative measure

Visual Stimulus (light flashing)

Perception of the light

Response

Visual Stimulus (light flashing)

Perception of the light

Response

DECISION

Subtraction TechniqueSubtraction Technique Activation in Activation in

control control condition is condition is subtracted from subtracted from experimental experimental condition to get condition to get activity due to activity due to stimulation in stimulation in the the experimental experimental conditioncondition

Effects of experienceEffects of experience

Experience-dependant plasticityExperience-dependant plasticity Developmental environment can affect Developmental environment can affect

neuron specializationneuron specialization Kittens raised in environment with only Kittens raised in environment with only

vertical lines had more of their brain devoted vertical lines had more of their brain devoted to recognizing vertical lines in adulthood (and to recognizing vertical lines in adulthood (and none devoted to horizontal)none devoted to horizontal)

Learning happens through changes in Learning happens through changes in connections and relationships between connections and relationships between neurons, even in adulthoodneurons, even in adulthood Greebles study (back to the FFA)Greebles study (back to the FFA)

GreeblesGreebles

Recall discussion of localization of Recall discussion of localization of functionfunction Fusiform Face Area (FFA) was an area in the Fusiform Face Area (FFA) was an area in the

Temporal lobe devoted to recognizing faces… Temporal lobe devoted to recognizing faces… or was it things we’re experts at or was it things we’re experts at recognizing??? recognizing???

Kanwisher has demonstrated, using fMRI, Kanwisher has demonstrated, using fMRI, that the area does selectively respond to facesthat the area does selectively respond to faces

Gauthier and colleagues showed fMRI Gauthier and colleagues showed fMRI evidence for experience-based plasticity in evidence for experience-based plasticity in this area (Greebles study)this area (Greebles study)

Greebles StudyGreebles Study Step 1: measure brain Step 1: measure brain

activity in FFA when viewing activity in FFA when viewing GreeblesGreebles

Step 2: train people to Step 2: train people to recognize individual Greebles recognize individual Greebles and families of Greeblesand families of Greebles

Step 3: measure brain Step 3: measure brain activity in FFA when viewing activity in FFA when viewing Greebles Greebles

Analysis: compare activity in Analysis: compare activity in FFA before and after trainingFFA before and after training

Greebles StudyGreebles Study

ConclusionsConclusions Plasticity of Plasticity of

FFAFFA FFA selects for FFA selects for

things we’re things we’re experts aboutexperts about

Faces are Faces are things we’re things we’re experts aboutexperts about

Memory and Cognition PSY 324 Topic 2: Cognition and the Brain Dr. Ellen Campana Arizona State...

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