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Unformatted text preview: Chapter 8: Cortical behavior
Behavior in the brain
Cortical areas according to brain lobe
Left and right brain
Some cortical functions / syndromes
Summary Behavior in the brain Behavior Sensory processing (sensation)
(perception) 1 Reception in the cortex: sensation (primary sensory area)
After reception: perception (association areas) Sensory processing Association areas and sensation
(perception) 1. Object
2. Image: from eye to brain => sensation (detection, gewaarwording)
3. Processing in the brain => perception (waarneming)
! Perception is possible without sensation
a subliminal stimulus passes below the normal limits of sensation FUNCTIONAL organization of the human cerebral cortex into 4 areas:
1. idiotypic cortex:
2. unimodal or modality specific association cortex: primary C.
higher order C. 3. heteromodal or multimodal association cortex: cognition 3. limbic and paralimbic cortex: emotion Hierarchical organization:
- sensation (detecting)
- perception (process of integrating, recognizing, interpreting)
each level contains functionally distinct areas
simultaneous analysis of a signal in different ways
(eg an unconscious and a conscious stream, dorsal and ventral stream) 2 Unimodal association areas
(secondary areas, higher order)
Primary areas have direct afferent (sensory) or
efferent (motor) connections with sensorory or motor
In rat, these areas occupy nearly all the cortex,
in human only 20% Multimodal association areas Anatomy
physiology, 4 Action starts from prim. motor c. structure
meet. Multimodal association areas
modulate information between
secondary areas 3 Fiber tracts (forming the white matter) connect different regions How do these different cortices work together? - Short loop pocesses do not need the cortex, eg tendon reflexes.
- Medium loop pocesses mediate rapid, but simple, responses (e.g.swapping a
- Long loop pocesses (e.g.writing down the name of a seen object), require the
complex processing power of the association areas. Unimodal Multimodal U-fibres connect adjacent zones
(Crevits, Mijn geest van vlees en bloed, 2007) 4 • Frontal lobes
– Three distinct areas:
• M1 primary motor cortex Cortical areas according to brain lobe
with emphasis on “higher” functions • PM premotor region
(motor association cortex)
• PF prefrontal region
(multimodal asso cortex) PFC (prefrontal cortex)
Damage may lead to an array of difficulties
e.g. intact IQ and academic skills,
but failure to organize a sequence of behaviors to attain a goal From a responsible, religious, respectable
and socially well-adapted man
to an irreverent, profane and impulsive
itinerant. Relatively immature in children
e.g. perseveration in young children; repeated behavior
1848, a milestone in neurosciences:
key parts of personality reside in the
These findings indirectly lead to the development of lobotomy to help some people
with severe mental derangement. 5 Phineas Gage’s skull
(The Warren Museum) The bar that was shot through the head of Mr. Phineas P. Gage at Cavendish,
Vermont, Sept. 14, 1848.
(Museum of the Medical College of Harvard University) The frontal lobe contains the prefrontal multimodal association area for
motor and sensory control (executive functions, working memory) Frontal lobotomie (Nobelprice to Moniz in 1949) Major areas of the prefrontal cortex Anterior cingulate 6 Prefrontal syndromes (classical view) Prefrontal syndromes (changing view) 1. Dorso-lateral-prefrontal cortex (DLPFC)
Executive functions, working memory
lesion: executive and memory dysfunctions Classical view:
Executive functions (problem solving, abstracting, planning, strategy
development and implementation) and working memory: DLPFC 2. Orbito-frontal cortex
Integration of (limbic) emotional and behavioral responses
lesion: dysfunctions of mood and personality disorders
3. Anterior cingulate cortex
lesion: obsessive-compulsive disorders Newer view:
-Metacognitive executive functions: cognitive control
problem solving, abstracting, planning, strategy development
and implementation, and working memory:
~ dorso-lateral-prefrontal cortex
-Emotional / motivational executive functions:
coordination of cognition and emotion
the ability to fulfill basic impulses following socially
~ orbito-frontal and medial frontal cortex
(Ardila A., Brain and Cognition 2008, 68, 92–99) The parietal lobe makes part of the parieto-temporo-occipital multimodal
association area Parietal cortex S1 primary somatosensory cortex
SA somatosensory association cortex
MMA multimodal association cortex
(attention, language, praxia, spatial orientation) 7 • Parietal association area • Parietal association area – effect of damage – Integration of information from various sensory modalities
– Integration of information from senses and information from
– Integration between individual’s internal state and the external
“where” an object is, requires integration of various information (where route) Attentional defects in right parietal lobe lesion – ALEXIA (inability to read)
AGRAPHIA (inability to write)
– APRAXIA (failure to generate purposeful movements)
e.g. can not stir milk in coffee, but can pantomime the action
– Loss of spatial processing and attentional deficits. Temporal cortex
Primary auditory cortex (BA 41)
Auditory association cortex (BA 42)
Wernicke area (BA 22) THE LATERAL TEMPORAL LOBE IS CRITICAL
FOR LANGUAGE AND MUSIC COMPREHENSION Left hemispatial neglect
The lack of attention to one side of space, usually the left, as a result of
(right) parietal lobe damage,
despite intact sensory and motor functioning.
The neglect is relative to the midline of the body.
In severe cases, the patient denies the left side of his own body
(hemisomatagnosia) Medial (limbic system)
MOVE AM amygdala
MB mammillary bodies
OB olfactory bulb THE MEDIAL TEMPORAL LOBE IS CRITICAL
FOR EMOTION AND MEMORY 8 Temporal cortex The lateral temporal lobe makes part of the multimodal parieto-temporooccipital multimodal association area => see language,
THE LATERAL TEMPORAL LOBE IS CRITICAL
FOR LANGUAGE AND MUSIC COMPREHENSION Auditory
THE MEDIAL TEMPORAL LOBE IS CRITICAL
FOR EMOTION AND MEMORY MOVE Occipital cortex
=> primary visual cortex (V1):
retinotopic organization Occipital cortex: naming in human and macaque Human segregation of visual information:
form, color, motion, depth, etc.
in visual association cortices Macaques 9 Occipital cortex: ‘What and Where’ pathways (MT) Higher visual pathways: SIMPLIFIED versus more REALISTIC Dominance in the brain Left and right brain
Dominance is defined by language 10 Lateralisation exists in different vertebrates
e.g. chicken (!!! in chickens, the visual pathway is entirely crossed)
left occipital Laterality right eye
right occipital cortex In the same time, chickens use their
-right eye (left occipital) to discriminate grains from littele stones (detail)
-left eye (right occipital) to notice predators (the Gestalt)
Advantage: two functions simultaneously
Disadvantage: when one cortex has been destroyed, that function has lost. And in humans?
Dominance is defined by language 96 % of righthanded people have their dominant hemisphere on the left
70 % of lefthanded people have their dominant hemisphere on the left
(Rasmussen, 1991) 11 Laterality and the influence of culture:
holistic versus analytic perception Dominant hemisphere lesion: aphasia
Arcuate fascicle Westerners tend to engage in context-independent and analytic
Asians tend to engage in context-dependent and holistic perceptual
processes Nisbett et al., Trends in Cognitive Sciences 2005, 9, 467-73 Nondominant hemisphere lesion
• Inattention (neglect for left side)
• Denial or unconcern
• Extinction (on double simultaneous sensory stimulation)
• Constructional apraxia
• Dressing apraxia
• Spatial disorientation 12 What do you see?
The large H
or the S? Aoccdrnig to rscheearch at Cmabrigde
Uinervtisy, it deosn't mttaer in waht
oredr the ltteers in a wrod are, the olny
iprmoetnt tihng is taht teh frist and lsat
ltteer be at the rghit pclae.
The rset can be a total mses and you
can sitll raed it wouthit porbelm.
Tihs is bcuseae the huamn mnid deos
not raed ervey lteter by istlef, but the
wrod as a wlohe. Gestalt The right hemisphere is
in face recognition Hearing in the brain PS
It would be wrong to think that only
the limbic system is involved in
The neocortex also plays part.
We sometimes have strong emotional
reactions only after consciously
thinking (by the neocortex). ? Vissarion Shebolin (1902-1963, conservatory of Moskou)
continued to compose after a left hemisphere stroke causing
aphasia 13 Hearing in the brain
Left hemisphere: rythm Right hemisphere:
melody (analytic) (holistic) Major cortical functions / syndromes The Sapir-Whorf hypothesis (the “linguistic relativity hypothesis")*
postulates a systematic relationship between the grammatical
categories of the language a person speaks
and how that person both understands the world and behaves in it. Language Hopi-indians in Arizona have no word
for present, past and future.
They have another notion of time.
This idea challenges the possibility
of perfectly representing the world
with language, because it implies that
the mechanisms of any language
condition the thoughts of its speaker community. *According to the antropologist Edward Sapir and his student Benjamin Whorf 14 The Sapir-Whorf hypothesis (the “linguistic relativity hypothesis") The Sapir-Whorf hypothesis (the “linguistic relativity hypothesis") Can we think without language? Can we think without language? not as detailed,
- deaf-mute persons do think
- aphasia patients have normal
non-verbal intelligence (Crevits L., 2007, Mijn geest van vlees en bloed) Communicative gesture in a baboon. An adult female intimidates another
individual by quickly rubbing her right hand on the ground. Language may have evolved from a gestural system "mirror neurons" might have given chimpanzees the mental power
to recognize subtle differences in hand gestures
in 2005, the first experiment showing that vocal sound of chimps
can carry meaning for chimpanzees
(Slocombe and Zuberbuhler, Oct. 2005, Current Biology) => perhaps language got its start with rough grunts, rather than
Report of the first evidence of strong population-level right-handedness in 60
captive baboons for a species-specific communicative manual gesture
supports the view that lateralization for language may have evolved from a
gestural system of communication controlled by the left hemisphere.
Behavioural Brain Research 171 (2006) 170–174 15 Intermezzo: mirror neurons
Mirror neurons fire both when an animal acts and when the animal
observes the same action performed by another. Theory of Mind (mind reading)
involves the amygdala, sup. temp. region, medial frontal and
orbitofrontal cortex Thus, the neuron "mirrors" the behavior of another animal, as though the observer
were itself acting.
They have been observed in primates, in humans and in some birds.
In humans, brain activity consistent with mirror neurons has been found in the
premotor cortex and the inferior parietal cortex
The function of the mirror system is a subject of further research.
Mirror neurons may be important for understanding the actions of other
people, and for learning new skills by imitation.
Some researchers argue that mirror systems contribute to the theory of mind.
Others relate mirror neurons to language abilities.
It has been proposed that problems with the mirror system may underlie some
disorders, especially autism. Typically impaired in autism … back to language
Language from gestures or from grunts?
Even if language got started with grunts (verbally),
mirror neurons may still have played an important part in the evolution of
communication. Interpreted in Language
speech - Some of the regions where monkeys have mirror neurons correspond
to areas of the human brain that handle language.
- What is more; mirror neurons are also linked to the ability to get inside
other people's heads and understand their intentions.
It is one thing to figure out why someone else is making a rough grunt. Auditory
cortex And … when you know that other people are trying to figure out what your
rough grunt means, you have got a conversation. 16 Aphasia: major historical landmarks
• Aphasia: acquired disorder of language
• Associated disorders:
– Agraphia Note: Dysarthria: disorder of the motor apparatus of speech Wernicke
• Broca (1861): patient with loss of speech, but good comprehension
• Wernicke (1874): fluent speech, but poor comprehension
• Lichtheim (1885): classic description of aphasic syndromes Broca: production of language: motor drive + grammar
motor (expressive, Broca) aphasia:
“… I house…walk … house”
sensory (receptive, Wernicke) aphasia:
“and when he walked, and the store closed, it was” PS
Even in language, both hemispheres work together Left hemisphere: phasia
- spoken language: aspects of affection, prosodia, singing
- written language:
if damaged => omission, wrong spliting, difficult to write on a
straight line, repeating of letters 17 Repeat spoken words Repeat written words From spoken or written words to speech Fundamental lessons from aphasia • Language processors are localized
• Language is distributed in the brain
• Language processors are regionally associated with different parts of the brain
in proximity to sensory or motor functions
cortex • Different language problems can be due to an underlying deficit in a single
language processor Visual cortex Finally, the motor cortex drives to move mouth, tongue … => speech 18 GNOSIA (recognition) Agnosia •A recognition (perception) problem (normal sensation)
•The inability to recognize objects when using a given sense and
when that sense is basically intact
•Modality specific: visual, auditive, tactile How do we know that dogs are dogs and not cats? Visual agnosia Agnosia in non-visual modalities
Auditory agnosia (sup. temp. lesions, usually bilateral)
Auditory sound agnosia
Amusia Tactile agnosia (inf. parietal / insula lesions)
Can not recognize objects by touch somatosensory association cortex
Visual agnosia: disorder of the vental stream 19 Hemispatial visual neglect Attentional defects PRAXIA: the generation of purposeful movements
APRAXIA: failure to generate purposeful movements
despite normal motor function
lesion mostly in left parietal cortex
Ideational A.: inability to describe
Ideomotor A.: can describe
can not pantomime These patients with right parietal damage typically orient eyes and head towards the
They were not looking to a certain target situated on the right side.
(The room was empty with only the photographer standing right in front of them.) 20 Ideational Apraxia Ideomotor Apraxia • Inability to correctly formulate the ideational concepts for
carrying out a multistep activity
in either site of the body
• Can pantomime • Inability to correctly perform learned skilled movements,
when this deficit cannot be attributed to weakness, sensory
• Great difficulty in attempting to pantomime an action (e.g.,
sawing a piece of wood, using a phone);
improves with repetition, and best when using actual object • Lesion: left parietal-temporal-occipital region
• Lesion: left inferior parietal lobe or SMA Executive functions (DLPFC) Classifications of apraxia
1. According to disturbed function:
- ideomotor A: left parietal
- ideational A: left parietal-temporal-occipital
2. According to location:
e.g.oral (bucco-facial) A: left anterior
3. According to prominent symptom:
e.g. constructive A: multiple locations
LHD03 M ODE L RHD01 LHD08 M ODE L RHD06 LHD01 M ODE L RHD10 The ability to think abstractly
and to plan, initiate, sequence, monitor, and stop
complex behaviour. LHD10 Executive dysfunction
associated with apathy, attention deficit (ADHD), negative
symptoms in schizophrenia, treatment response in
depression... M ODE L RHD05 Different projections
from the subcortex to
the DLPFC. 21 Executive functions and attention Executive functions and solving of conflicts Selective attention (concentration on one source of information)
can be conceptualized:
- as an executive process an sich – or,
- as an essential component of different executive processes ACC: recognition and correction of the conflict
DLPFC: monitoring of goals and allocation of selective attention ⇒ executive functions are closely related to working memory and attention
central executive in the working memory model of Baddeley
supervisory attentional system (SAS) in the Norman &Shallice model ACC: intermediate function in emotional control
subjective experience of pain. ACC DLPFC Memory Processes: R-R-R-(R)
Registration - Retention - Retrieval (Reproduction)
Rehearsal Sight Memory Elaboration
Organization Smell Sound Sensory
Memory Attention Short-Term
Retrieval Taste Touch Lost Lost Control processes:
attention, rehearsal, coding, retrieval 22 During the process of LTM, two kinds of changes occur:
2. Working Memory Development of new synapses (synaptogenesis), esp in childhood
Modulation of synaptic connections giving rise to networks with
permanent structural changes
through long term potentiation and long term depression
LTP is a mechanism by which short-term memories move into long-term
storage. Declarative memory refers to all memories that are consciously available. These are
encoded by the hippocampus, but consolidated and stored in the neocortex.
Declarative memory has two major subdivisions:
Episodic memory refers to memory for specific events in time.
Semantic memory refers to knowledge about the external world,
e.g.the function of a pencil, the name of the president.
Procedural memory refers to the use of objects or movements of the body, such as
how exactly to use a pencil or ride a bicycle.
This type of memory is encoded and stored by the basal ganglia, cerebellum and
supplementary motor cortex. Two glutamate receptors: AMPA: alfa-amino-3-hydroxy-5methyl-4-isoxazole-propionic acid
NMDA: N-methyl-D-aspartate Long-term potentiation (LTP) Hippocampus
CA1 The CA1 region of the hippocampus is
essential for long-term memory.
Over time, these synapses become
=> a constant level of presynaptic
stimulation becomes converted into a larger
postsynaptic output: LTP. Mg-ions block
the canal glutamate no influx LTP in rat brains coincides with the
formation of additional synapses between
the presynaptic axon terminal and the
dendrite it synapses with.
LTP has also been demonstrated in neurons
of the cerebellum. influx of Na+ Toni, N., et al, Nature, 25 Nov 1999 enhanced influx of Na+ influx of Na+
and Ca2+ The AMPA-receptors let enter Na+, after binding to glutamate.
Mg-ions block the canal of the NMDA-receptor and prevent the influx of ions.
When the cell is partially depolarised, Mg-ions move away. Na+ and Ca2+ can enter
the cell. 23 Long-Term Depression (LTD)
Ca2+ ions flow into the cell through the NMDA receptors and bind to calmodulin.
This activates calcium-calmodulin-dependent kinase II (CaMKII).
CaMKII phosphorylates AMPA receptors making them more permeable to
the inflow of Na+ ions and thus increasing the sensitivity of the cell to
depolarization. Slow, weak stimulation of CA1 neurons brings about long-term
changes in the synapses.
In case of LTD, a reduction in the sensitivity occurs: Glu binds to
a different type of NMDA receptor. CaMKII may also increase the number of AMPA receptors at the synapse.
Increased gene expression (i.e. protein synthesis, perhaps of AMPA receptors)
also occurs during the development of LTP.
Additional synapses may also form during the formation of LTP. Long-term depression occurs in the cerebellum of mice during the
development of a conditioned response. Memory Processes: anatomy
• Ultra short term memory (sensory)
• Short term memory (working): prefrontal cortex
ability to recall things within 10 sec.
and to do something with that info
– Must be rehearsed to keep it there longer
– Lost if not transferred to long term memory Four
systems DLPFC • Long term memory: information retained
Declarative memory (explicit):
- Episodic: medial temporal (hippocampus)
- Semantic: lateral temporal
Procedural memory (implicit):
Basal ganglia, cerebellum and supplementary motor cortex
Episodic memory (medial temporal lobe) 24 Interaction of different brain regions
in encoding and retrieval Episodic memory (medial temporal lobe):
circuit of Papez, the hippocampo-mammillo-thalamic axis
(hippocampus-fornix-mammilary body-thalamus-cingulate-neocortex) Retrograde and anterograde amnesia Retrospective and prospective memory
Retrospective memory: see abobe
remembering to remember or
remembering to perform an intended action. Retrograde amnesia: a form of amnesia where someone will be unable to
recall events that occurred before the onset of amnesia.
Anterograde amnesia: a loss of memory of what happens after the event
that caused the amnesia. Instead of recalling past actions events, or knowledge
prospective memory is self-initiated and does not operate
directly on external stimuli.
e.g. remembering to take certain documents to the office, remembering to
call someone at night, remembering to take a medicine in the evening. 25 Suppression of memory
It is clear that remembering is not exactly reproducing.
Memory is a dynamic process that (easily) can be influenced e.g. by
emotions. Not only the sensation, and the perception are distortions of reality,
memory also is a modulated reproduction.
While subjects try to suppress memories, the prefrontal
cortex becomes more active and the hippocampus less
active. Crevits L., Mijn geest van vlees en bloed, 2007 False memories
Our memories are coloured and distorted! cf experiment FUNCTIONAL organization of the human cerebral cortex into 4 areas:
1. idiotypic cortex: What was the speed of these cars when
they touched each other
40 The brain is very flexible,
ever making new connections (experience).
People with frontal damage are very susceptible to false memories, even to
because their frontal control mechanism (the monitor) has been lesioned. 2. unimodal or modality specific associationcortex: primary C.
higher order 3. heteromodal or multimodal associationcortex: cognition 3. limbic and paralimbic cortex: emotion 26 Left and right brain work togheter Structures connecting both
commissura posterior The cortex needs … the corpus callosum c. callosum comm. commissura
anterior posterior The cortex needs … the corpus callosum Pioneer: Sperry (Nobelprice 1981) Humans:
Experiments with tachistoscope
(~ section of chiasma opticum) Experiments with rats:
section of corpus callosum
& optic chiasm Seen from the standpoint of the testperson 27 The cortex needs … the corpus callosum
Seen from the standpoint of the testperson Humans:
Experiments with tachistoscope
(~ section of chiasma opticum)
(~ section of corpus callosum) Chimera composed of 2 half faces,
exposed for 0.15 s in a tachistoscope. With spoken response (LH), the patient retrieves the right face.
With pointing (non-verbal, RH), the patient chooses the left face. Cognitive functions contributing to mental performance are
distinct but heavily intermingled. 28 ...
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This note was uploaded on 05/28/2010 for the course GE BIOL020000 taught by Professor Luccrevits during the Spring '10 term at Ghent University.
- Spring '10