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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