Summary Brain & Cognition II
Lecture 1: hemispheric specialization
Lateralization of sensory processing and motor output: left visual field, sound, touch right
hemisphere left arm, leg, etc.
Motor not absolute, particularly proximal muscles (shoulder) largely bilateral, distal movement
(fingers) contralateral, dominant hand ipsilateral.
The Wada test: testing in what half language is represented (most people left hemisphere). Anesthetic
in left hemisphere aphesia: inability to speak or comprehend language. Left cannot remember after
regaining consciousness, right can remember but cannot express verbally, only manually.
- Sylvian Fissure much flatter on left: difference size Heschl’s gyrus and Planum Temporale,
Wernicke’s area (understanding language). Doesn’t seem to be the case, size left versus right
Heschl’s gyrus does not match language lateralization as measured with Wada test.
- No difference gray matter density planum temporale, but clear difference gray matter Broca’s
area (speech production)
o Speech production more bilateralized?
o Wada test mainly tests production?
Other differences left and right:
- Pyramidal cell bodies larger on left than right in Heschl’s gyrus
- Connections between cells are organized in patches, these patches are equally large in left and
right (area 22; similar to Wernicke’s), but more distant apart in left.
Normally brain hemispheres work together, connection via corpus callosum (fibers). Important for
seeing “whole scene”. Connection between (mostly) homotopic and heterotopic areas. Together with
anterior commissure, posterior commissure connects subcortical nuclei.
Split brain patients (removing corpus callosum because of epilepsy)
Seems to not effect personality, intellect, sensory or motor performance. Two minds, advantages:
better at drawing two asymmetrical shapes with both hands, higher leven functions work
independently (independently search for targets).
Left hemisphere Right hemisphere
Language & speech Visuospatial / geometrical tasks (block design
task left hand)
(Can recognize with verbal cues such as Recognizing / matching faces (FFA)
haircolor) Recognizing self
Perceptual organization (right hemisphere lesion
apperceptive / integrative agnosia)
Local information (details) Global information (hierarchal letter task:
Navon task)
Brain interpreter: post hoc rationalization. Maximizing (statistical)
Analytical, finding motivations, patterns
(matching over maximizing)
Left: details, analytic, linguistic, predictive
Right: big picture, holistic, visual, statistical
1
, Lecture 2: action
Hierarchal organization of motor pathways
Final common pathway: alpha motor neuron & stretch reflex
ALS affects alpha motor neurons, polio: viral infection that attacks alpha motor neurons,
Dorsolateral: distal muscles, fine movements
Ventromedial: proximal muscles, posture
Central pattern generator: spinal cord can do walking on its own (without cerebellum).
Stretch reflex: keeping posture: muscle spindle senses stretching activates alpha motor neuron
muscle contracts (input from pons). Reciprocal inhibition of antagonistic muscle: the other side has
to relax.
Crossed extensor reflex: as one limb flexes, the other extends. Flexor & extensor.
Golgi tendon reflex: protecting from overload, muscle relaxes and you drop load.
Withdrawal reflex: reflexing from damage (sharp or hot).
Lower motor control
Reflexes “do all the work” only thing needed is central command: pyramidal system.
Extrapyramidal system
- Rubrospinal: track + red nucleus: muscle tone & distal fine movements
- Tectospinal: superior & inferior colliculi: receive visual (superior) and auditory (inferior)
info, reflex like orienting response
- Vestibulospinal: vestibulocochlear nerve (inner ear): posture, balance
- Reticulospinal: staying awake, arousal, excitability
Pyramidal system
- Corticobulbar: cortex brainstem. Towards cranial nerve nuclei that move face.
- Corticospinal: cortex spinal cord
o Damage: paralysis: Babinski sign: sharp object on foot: normal foot flexes, damage
foot extends
2
Lecture 1: hemispheric specialization
Lateralization of sensory processing and motor output: left visual field, sound, touch right
hemisphere left arm, leg, etc.
Motor not absolute, particularly proximal muscles (shoulder) largely bilateral, distal movement
(fingers) contralateral, dominant hand ipsilateral.
The Wada test: testing in what half language is represented (most people left hemisphere). Anesthetic
in left hemisphere aphesia: inability to speak or comprehend language. Left cannot remember after
regaining consciousness, right can remember but cannot express verbally, only manually.
- Sylvian Fissure much flatter on left: difference size Heschl’s gyrus and Planum Temporale,
Wernicke’s area (understanding language). Doesn’t seem to be the case, size left versus right
Heschl’s gyrus does not match language lateralization as measured with Wada test.
- No difference gray matter density planum temporale, but clear difference gray matter Broca’s
area (speech production)
o Speech production more bilateralized?
o Wada test mainly tests production?
Other differences left and right:
- Pyramidal cell bodies larger on left than right in Heschl’s gyrus
- Connections between cells are organized in patches, these patches are equally large in left and
right (area 22; similar to Wernicke’s), but more distant apart in left.
Normally brain hemispheres work together, connection via corpus callosum (fibers). Important for
seeing “whole scene”. Connection between (mostly) homotopic and heterotopic areas. Together with
anterior commissure, posterior commissure connects subcortical nuclei.
Split brain patients (removing corpus callosum because of epilepsy)
Seems to not effect personality, intellect, sensory or motor performance. Two minds, advantages:
better at drawing two asymmetrical shapes with both hands, higher leven functions work
independently (independently search for targets).
Left hemisphere Right hemisphere
Language & speech Visuospatial / geometrical tasks (block design
task left hand)
(Can recognize with verbal cues such as Recognizing / matching faces (FFA)
haircolor) Recognizing self
Perceptual organization (right hemisphere lesion
apperceptive / integrative agnosia)
Local information (details) Global information (hierarchal letter task:
Navon task)
Brain interpreter: post hoc rationalization. Maximizing (statistical)
Analytical, finding motivations, patterns
(matching over maximizing)
Left: details, analytic, linguistic, predictive
Right: big picture, holistic, visual, statistical
1
, Lecture 2: action
Hierarchal organization of motor pathways
Final common pathway: alpha motor neuron & stretch reflex
ALS affects alpha motor neurons, polio: viral infection that attacks alpha motor neurons,
Dorsolateral: distal muscles, fine movements
Ventromedial: proximal muscles, posture
Central pattern generator: spinal cord can do walking on its own (without cerebellum).
Stretch reflex: keeping posture: muscle spindle senses stretching activates alpha motor neuron
muscle contracts (input from pons). Reciprocal inhibition of antagonistic muscle: the other side has
to relax.
Crossed extensor reflex: as one limb flexes, the other extends. Flexor & extensor.
Golgi tendon reflex: protecting from overload, muscle relaxes and you drop load.
Withdrawal reflex: reflexing from damage (sharp or hot).
Lower motor control
Reflexes “do all the work” only thing needed is central command: pyramidal system.
Extrapyramidal system
- Rubrospinal: track + red nucleus: muscle tone & distal fine movements
- Tectospinal: superior & inferior colliculi: receive visual (superior) and auditory (inferior)
info, reflex like orienting response
- Vestibulospinal: vestibulocochlear nerve (inner ear): posture, balance
- Reticulospinal: staying awake, arousal, excitability
Pyramidal system
- Corticobulbar: cortex brainstem. Towards cranial nerve nuclei that move face.
- Corticospinal: cortex spinal cord
o Damage: paralysis: Babinski sign: sharp object on foot: normal foot flexes, damage
foot extends
2
