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Association cortex (Ch 26)

Microcircuitsthe interfacegenes

cellssynapses

actionperceptscognition

The challenge!

Motor Map forEye- and Orientation Movements

CNS INFRASTRUCTURE (ex motor beh)Neuronal networks that co-ordinate different movements – relevant for other functions also!

Protective reflexesSwallowing CPG

Respiratory CPGLocomotor CPGs

Postural networksChewing CPG

Express. of emotionsEye motor map

Reaching

SelectionSequencing

timing

Reticulospinal

MLR – DLR Brainstem Locomotor Command

CPG

Movements

Spinal Pattern Generation

lamprey to manSensoryfeedback

Selection of Motor programs

Neural control of goal-directed movements

SteeringTectum

PostureVestibular

Basal ganglia

Cortex

Thalamus

Reticulospinal

MLR – DLR Locomotor Command

CPG

Movements

Spinal Pattern Generation

Sensoryfeedback

Selection of Motor programs

Neural control of Goal-directed locomotion

SteeringTectum

PostureVestibular

Basal ganglia

Cortex

Thalamus

Spinal organisation

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Reticulospinal

MLR – DLR Locomotor Command

CPG

Movements

Spinal Pattern Generation

Sensoryfeedback

Selection of Motor programs

Neural control of goal-directed behaviour

SteeringTectum

PostureVestibular

Basal ganglia

Cortex

ThalamusCortex areas

Striatum

Pallidum/Subst. nigra reticulata

CPG CPG CPG

command command command

Thalamus

Sensory input

DA

locomotion Posture, etc saccades

Control of (motor) behaviour

excitation (glut.)inhibition(GABA) DA-modulation

Cortex

input layer - striatum

output layer with tonic inhibition – pallidum

CPG CPG CPG

command command command

Thalamus

Sensory input

DA

e.g. Locomotion Emotional exp Eye saccades

Forebrain control of Adaptive behaviour in the absence of neocortex

excitation (glut.)inhibition(GABA) DA-modulation

Cat without neocortex examining whether it can find support below the edge of the box

It can also:get hungry or thirsty – search for food and eatremember the location of the food in a T-maze find the way out of a complex mazedisplay aggressive behavior towards other catsConclusion: a very large part of the neural machinery for goal-directed motor

behaviour is subcortical

From Bjursten, Norrsell & Norrsell 1976

Film from a study by Bjursten, Norrsell & Norrsell 1976

Information through:

Functional Brain Imaging(fMRI, PET, etc)

Brain “damaged” persons

Cognitive tests, etc

Studying of other species

Cortex – an additional module, with various roles

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Brain Size and Function of Cortex?

The Brain - Some repetition

Types of Cerebral Cortex

NeocortexNewest in evolutionAbout 90% of total6 layers, most complex

PaleocortexAssociated with olfactory system (piriform cortex), the

parahippocampal gyrus, uncusfewer than 6 layers (3 layers)

ArchicortexHippocampal formation; limbic systemfewer than 6 layers (3-4 layers), most primitive

MesocortexCingulate gyrusTransitional between archicortex and neocortex

Histology of the Cerebral Cortex

2 main cell types are pyramidal and granule cells

Pyramidal cells have large apical dendrite and basal dendrites

Axon projects downward into subcortical white matter

Pyramidal cell is the primary output neuron

Granule (stellate) cells are interneuronsShort dendrites extending in all directionsShort axon projecting to adjacent pyramidal

cellsGranule cells are especially numerous in

sensory and association cortex

Neocortex has 6 layers designated I, II, III, IV, V, VI

Pyramidal cells predominate in layers III and V

Granule cells in layers II and IV

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Types of Cortex

Cytoarchitecture varies in different areasNumber and size of cellsThickness of layers

A More Detailed Look at Cortical LaminationPN26BA0.JPG

Structure of the Human Neocortex Including Association CorticesPN26022.JPG

Brodmann’s areasCortical Columns (minicolumn – macro/hypercolumn)

Functional units are cortical columns (directions, frequencies, parts of body, etc)Columns are vertically oriented groups of thousands of neurons in synaptic contactMain input layer is layer IV which receives thalamic inputThalamus is the main source of input to the cortex

.

Buxhoeveden, D. P. et al. Brain 2002 125:935-951

Human foetal columns at ~26 gestational weeks

Canonical Neocortical Circuitry – 6 layersPN26030.JPG

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Neurochemical systems involved in modulating the function

Norepinephrine

Dopamine

Serotonin

Acetylcholine

• Flight/Fight/Fright

• Pleasure seeking/executive

• Appetitive functions

• Memory, arousal

Functional Histology - summary

Layers V and VI = outputV to Basal ganglia, brainstem and spinal cordVI to thalamus

Layers I, II, III = associative; projecting to cortical areasLayer IV = layer receiving inputs from thalamus and other cortical areas

Summary of the Overall Connectivity of the Association CorticesPN26040.JPG

The Brain: Lobes

Occipital LobesTemporal LobesParietal LobesFrontal Lobes(sometimes alsoLimbic LobesInsular Lobes)

Neuroanatomy - Parietal Lobes

Functions:• Sensory integration, visual attention, perceptual awareness, attention

Lesions can cause:• Neglect, inattention, dyscalculia, anomia, agraphia (writing problems), alexia (reading problems), apraxia (orient to sound)

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Parietal Neglect Syndrome

Failure to recognize side of body contralateral to injury

May not bathe contralateral side of body or shave contralateral side of face

Deny own limbs

Objects in contralateral visual field ignored

Locations of the Underlying Lesions in Patients Diagnosed With Contralateral Neglect SyndromePN26061.JPG

Locations of the Underlying Lesions in Patients Diagnosed With Contralateral Neglect SyndromePN26062.JPG

The Right Parietal Cortex of Normal Subjects is Highly Active During Tasks Requiring Attention

Note: “better” to damage left part

Neuroanatomy - Temporal Lobes

Functions:• Memory, auditory processing, object recognition and identifying, naming

Lesions can cause:• Amnesia, Wernicke’s aphasia (more if left side affected), agnosias, prosopagnosia (if right side damaged - faces not recognized), category specific deficits.

Neuroanatomy - Frontal Lobes

Can be divided into:• Motor: Control of movement

- weakness / paralysis

• Premotor: Integration of motor skills / learned action- uncoordinated movements / impaired motor skills / speech

• Prefrontal: Complex cognitive functions- difficulties with planning / decision making / inhibition / memory

/ attention / perseveration / personality changes / aphasia etc etc.

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PsychosurgeryPN26BB0.JPG

Neuroanatomy - Occipital Lobes

Functions:• Sensory integration, visuoperception, vision

Lesions can cause:• Heminopia, Blindsight, Visual Agnosia, Colour Agnosia

Recording From Single Neurons in the Brain of an Awake, Behaving Rhesus MonkeyPN26092.JPG

Typical experimental approaches – role of different lobe neurons:

Selective Activation of Neurons in the Parietal Cortex During Fixation of a Significant Visual TargetPN26101.JPG

Selective Activation of Neurons in the Parietal Cortex During Fixation of a Significant Visual TargetPN26102.JPG

“Attention”neuron

Selective Activation of Face Cells in the Inferior Temporal Cortex of a Rhesus MonkeyPN26111.JPG

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“Recognition” neuron

Selective Activation of Face Cells in the Inferior Temporal Cortex of a Rhesus MonkeyPN26112.JPG

“Recognition” neuron

Selective Activation of Face Cells in the Inferior Temporal Cortex of a Rhesus MonkeyPN26113.JPG

Activation of Neurons Near the Principal Sulcus of the Frontal Lobe During Delayed Response TaskPN26121.JPG

Finding “Planning” neurons

Activation of Neurons Near the Principal Sulcus of the Frontal Lobe During Delayed Response TaskPN26122.JPG

“Planning” neurons

Cellular evidence supports the importance of continuous activity

Neuron does not continue to fire during delay period; animal makes incorrect response

Correct response

Ehrsson, H. H. et al. J. Neurosci. 2005;25:10564-10573

Example of complexity - The somatic rubber-hand illusion

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Neuropsychological Testing – Wisconsin Card Sorting Task Neuropsychological Testing – Stroop Interference Test

GREEN YELLOW

BLUE BLUE

YELLOW GREEN

BLUE RED

Testing:

Attention

Automaticity

Learning

Response Selection

Word Reading

Color cognition

rabbit

Anatomy of the mind – more complete view

Perception and memory (“cognition”)

Feeling and expression (“affect”)

Thinking and action (“conation”)

Neocortex and hippocampus

Amygdala-hippocampusand cingulate

Prefrontal cortex and basal ganglia

Superiortemporal

Inferior parietal

Dorsal prefrontal

The hardware of cognition: The neocortexassociation regions.

Thalamus

Cingulate

Amygdala Hippocampus

Mamillary body Ant thalamic nuclei

Fornix

The hardware of emotions: The limbic system. 28.4 Modern conception of the limbic system. (Part 1)

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The hardware of “executive” functions: The corticostriatal structures.

vCaudate

Putamen

VentromedialPFC andCingulate( evaluative)

DorsolateralPFC ( executive)

Disorders of Perceptionand memory:

Sensory inputs

Thalamus

Arousal

Selective attention

Working memory

Associationcortex

Hippocampus

Consolidation

Storage

ADHD, Schizo-phrenia, Alzheimer’s

Emotionalencoding

CingulateEmotionalexperience

Amygdala

Disorders of emotionregulation

Endocrine AutonomicHypothalamusSensory inputs

ThalamusArousal

Selective attention

Working memory

Associationcortex

Hippocampus

Consolidation

Storage

Anxiety, Depression, PTSD

CingulateSelective attention

Workingmemory

Prefrontalcortex

Sensory inputs

ThalamusArousal

Amygdala Hippocampus

Storage

ConsolidationEmotionalencoding Disorders

of executivefunctions

psychosis,OCD.

Frontal executivesystemMotor system,Basal ganglia,cerebellum

Study questions for The Association Cortices

1. Describe the basic organizational features of neocortex, shared by association cortices and sensory and motor cortices.

2. What features distinguish association cortices from sensory and motor cortices? Consider thalamic input and corticocortical connections.

3. On what basis did Brodmann decide where to put the boundaries between Brodmann’s areas?

4. What are the main function(s) of (a) parietal association cortex, (b) temporal association cortex, and (c) frontal association cortex? What techniques and approaches have been used to reveal these functions?

5. What does the study of agnosias contribute to cognitive neuroscience?

6. What does contralateral neglect syndrome suggest about the neuroanatomy of attention? Why does contralateral neglect result from damage to the right, but not left, parietal lobe cortex?

7. Where and what are “recognition neurons,” “planning neurons,” and “attention neurons”?

8. What cortical region is particularly critical for the delayed response task?

9. Is brain size a good measure of intelligence? Explain.

Key Terms: agnosias, apraxia, cognition, contralateral neglect syndrome, corticocortical connections,cytoarchitectonic areas, delayed response task, interhemispheric connections, medial dorsal nuclei,Neocortex, prosopagnosia, pulvinar

Language, lateralization (Ch 27)

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Language Acquisition – what happened?

1. Language is universal across all human societies. That is, all societies use language in similar ways.

2. Despite the apparent diversity of human languages, any language can be learned by anybody.

3. Accordingly, languages must have some common underlying structures.

Universal Grammar (UG; Chomsky, 1965): A set of abstract general (and innate) principles that are universal to all natural languages. Each language is nothing but a specific implementation of these principles (e.g., temperature by F, C or K)

Speech perception is very difficult

Understanding language is even more difficult Language is hierarchical and can be extremely ambiguous

Animal CommunicationWhat is communication?One possible definition (E.O. Wilson)

Do animals communicate? Yes, lots! (and plants too)So what’s special about us? Reference? Complexity? Acquisition?

“Communication occurs when the action of or cue given by one organism is perceived by and thus alters the … behaviour in another organism in a

fashion adaptive to either one of both”

Vervet Language?

Vervet monkey gives different alarm call for three predators:EaglesSnakesLeopards

Are these referential?Closed system – mostly innate.

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Bee Language?

Honey Bees communicate about:-What direction to look for

nectar-How far away it is-How good it is

Easily as complex as information in a sentence of human language

Songbird Language?

Song in some species is learned

Regional “dialects”

Not really saying much

Human Language…

Digital infinity/recursion

Allows us unbounded expression –we can talk about anything

This is the farmer sowing the corn, that kept the cock that crowed in the morn, that waked the priest all shaven and shorn, that married the man all tattered and torn, that kissed the maiden all forlorn, that milked the cow with the crumpled horn, that tossed the dog, that worried the cat, that killed the rat, that ate the malt, that lay in the house that Jack built.

So is it a gradual or a Big Bang development?

Could language evolve gradually, or as one improbable mutation?

We need fossils of early protolanguage

Living fossilsEarly child languagePidgin languagesTrained chimps

PROTOLANGUAGE:

• No closed-class words

• No grammatical endings/morphology

• No embedding, relative clauses etc.

• No established word-order

Chimps’ and Other Apes’ Language?

Language used from 6 months (critical period?)

Able to understand some syntax

1. Go get the carrot that’s in the oven2. Put jelly in milk3. Put milk in jelly

KenziChildren’s language acquisition

12 - 13 months name objects18 – 20 months one-word sentences18 – 24 months two-word sentences

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Anatomy - The vocal tract

Vowels [a], [i], [u] only possible in homo sapiens (not in Neanderthals?)

Dangerous skill – we can choke!

Social Organization

Group size related to size of brainHuman group size: 150

Grooming holds together groupsHow can we groom? Use gossip!

Speech and handedness – a link to be understood?

The makers of stone tools were mostly right handed.

Chimps can make stone tools – they don’t do that in the wild – but when they do in experiments in captivity, they do not show any preference for right- or left handedness (Stanley Ambrose, Science 2001).

Maybe there is advantages in lateralization in bimanual tasks requiring precision and power (both in some chimps in Tanzania and among humans females more right-handed females than males, Am J Phys Anthropol, 123:62-8, 2004)

Handedness is probably associated with lateralization of the brain, as is language.

The speech area of the brain is adjacent to the area devoted to the control of the human hand.

Corpus callosum fibres have similar conductance speeds across species suggesting that in bigger brains lateralization may be favoured (Braz J Med Biol Res, 36:409-20,2003)

Lateralization of language function

Left brain: 97-98% of right-handed people have almost all of the language functions represented in the left-hemisphere of the neocortex

Right-hemisphere processes language functions regarding metaphorical or artistic meaning of language (e.g., humor)

In left-handed people, language function is more often represented predominantly in the right-hemisphere of the neocortex

The Major Brain Areas Involved in the Comprehension and Production of LanguagePN27010.JPG

Relationship of Language Areas to the Cytoarchitectonic Map of Cerebral CortexPN27020.JPG

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Schematic model (oversimplified)

Broca Wernicke

Concepts

Broca’s AreaProduction of spoken language

(Motor programs for controlling

speech sounds)

Wernicke’s AreaComprehension of language

(Interpretation of spoken and written words)

Arcuate fasciculusConnection between Broca’s

and Wernicke’s areasVisual CortexProcessing of written languageAngula GyrusConnection among Broca’s,

Wernicke’s and visual cortexMortor Cortex

Making of speech sounds (i.e. controlling of vocal muscles)

MODEL MODEL

Varieties of Aphasia

Broca's aphasia:- Damage to Broca’s area- Prevent a person from producing speech.- Nonfluent, telegraphic speech - Words are not properly formed(e.g.)

“I’m a sig … no… man … uh, well, … again.”“Well..mess..uh..sgga..diz..es..”

- Person can understand language

Wernicke's aphasia:- Damage to Wernicke’s area- Loss of the ability to understand language- Fluent but unintelligent speech - Can form words properly but the words that are put together

make no sense(e.g.)

“I go to a dog of cookies in TV”

Conduction aphasia:- Damage to Arcuate fasciculus- Fluent speech/good comprehension, but unable to repeat what is

head or read

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Acquired alexia:- Damaged connection

between visual cortex and Wernicke’s area

- Inability to read, but can see words

Agraphia:- Inability to write words - damages to where??

Dyslexia:- loss & deficits of

reading skills, spelling and recognizing word sounds

NEURAL ABNORMALITIES IN DYSLEXIA

Anomalies in cortical cell arrangementEctopias: unusual groupings of cells in outer layersMicropolygyria: excessive cortical foldingDisoriented cells

These abnormalities probably occur during neural migration during fetal development

BRAIN IMAGING DYSLEXIA

fMRI studies show different patterns of brain activation in dyslexics and nondyslexics.

Dyslexic subjects:showed less activation in posterior regions (e.g. Wernicke’s area)

and overactivity in anterior regions compared to nondyslexics.showed less activation of visual cortex in response to written

words.

ASSESSMENTS OF CEREBRAL LATERALIZATION

Sodium Amytal TestDichotic Listening Test Tachistoscopic Tests with Split-Brain patientsFunctional Brain Imaging

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Confirmation of Linguistic Specialization of the Left Hemisphere in HumansPN27030.JPG

Signing Deficits in Deaf Individuals who Suffered Lesions of Language Areas in the Left HemispherePN27080.JPG

Asymmetry of the Right and Left Human Temporal LobesPN27040.JPG HandednessPN27BC0.JPG

Cortical Mapping of the Language Areas in the Left Cerebral Cortex During Neurosurgery

PN27050.JPG

Right HemisphereLeft Hemisphere

Lateralization is a general phenomenon

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Lateralization

Left Hemisphere

Verbal competence

Speaking, reading, thinking & reasoning

Processes info in sequence

One piece of data at a time

Logical

Right Hemisphere

Nonverbal areas

Comprehension, spatial relationships, drawing, music, emotion

Processes info. as a wholeintuitive

Study questions

1. What is language? Is it unique to humans? Explain.

2. Compare the language functions of the right and left hemispheres. What techniques have been used to investigate cerebral lateralization (hemispheric specialization)?

3. Where is Broca’s area? Wernicke’s area? Compare Wernicke’s aphasia and Broca’s aphasia. What can the variety of aphasias tell us about the neural basis of language?

4. What similarities between sign language and spoken language suggest that they have common neural substrates?

5. Is hemispheric specialization in language functions unique to humans? Discuss.

6. What is the relationship between handedness, lateralization of language, and anatomical hemispheric asymmetry?

7. What evidence suggests the importance of biological constraints or predispositions in language learning?

8. If a split-brain patient is briefly shown a pencil in her left visual field, will she be able to describe the pencil? Which hand would she use to select the pencil by feel from a set of test objects? Explain with the aid of a diagram.

Key Terms: aphasias, aprosodias, Broca’s aphasia, Broca’s area, conduction aphasia, expressive aphasia, grammar, motor aphasia, phoneme, planum temporale, prosodic elements, receptive aphasia, sensory aphasia, split-brain patients, syntax, vocal folds, Wernicke’s aphasia, Wernicke’s area

Emotion and Lateralization

Left Hemisphere

Important for the expression of positive emotion

Damage to the L.H. leads to loss of the capacity of joy.

Activation in the L.H. leads to tendencies to approach other people.

Right Hemisphere

Important for the expression of negative emotion

Damage to the R.H. may make people euphoric.

Activation in the R.H. leads to tendencies to withdraw from people.

Emotion

What is emotion?Feeling, or affect, that can involve

physiological arousal, conscious experience, and behavioral expression

Emotion as Rationality

The relation between emotional states and cognitive states is the need to draw conclusions when cognition would face combinatorial explosion of possible reasoning threads

Emotions

Basic affectsSurprise Happiness InterestAnger Fear DisgustSadnessShame(note we have “motor

programmes” for expression of all these!)

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Theories of Emotion

* Emotion results from physiological states triggered by stimuli in the environment

* Emotion and physiological reactions occur simultaneously

Biology of Emotion

PET studies have shown that disgust, sadness, and happiness all activate the thalamus and prefrontal cortex

Autonomic Nervous System is activated in many emotions

Orbitofrontal Cortex:Involved in assessing the potential reward value of situations and objectsInvolved in processing of emotional cuesDamage causes inappropriate interpersonal interactions and generally insensitive to the emotional expression of othersDamage is associated excessive aggression and violence

Happiness and sadness activate hypothalamus

Fear activates amygdala (quick processing)

Disgust activate the insula (related to gustatory reaction to unpleasant tastes and smells)

Important brain structures for emotion

Behavioural Neurology, 1998,11:233 - 244

Differential contribution of right and left amygdala to affective information processing

Hans J. Markowitsch

Right: more negative

Left: activated by more positive stimuli, language related

Amygdala - example

Box D Fear and the Human Amygdala: A Case Study (Part 2)

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28.6 Model of associative learning in the amygdala relevant to emotional function.

Emotion-communication (not just info processing)?

Emotions as communication:Emotions are the fastest way that we can

communicate with members of our groupEmotions are signals between animals of the

same species that communicate one's brainstate to another

Emotions may predate language itself as a formof communication

Facial expression is inevitable like language anduniversal like language

Positive and negative emotions can coexist and are governed by different types of behavior.

Evidence for separate systems in the brain for approach emotions, such as happiness, and withdrawal emotions, such as fear.

The left frontal lobes are more active in approach emotions, and the right frontal lobes are more active in withdrawal emotions.

People who have more activation in the left frontal lobe tend to be more optimistic than people who have dominant right frontal lobe activity.

Clinically depressed people tend to have low left frontal lobe activity.

http://freescienceonline.blogspot.com/2006/12/cognitive-computing-consciousness.html

http://www.ted.com/talks/henry_markram_supercomputing_the_brain_s_secrets.html

The Blue Brain Project – building a cortical column

Proj leader: Henry Markram