7120 Lecture Notes - Lecture 9: Anterior Commissure, Commissure, Anticonvulsant
21 Jun 2018
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LECTURE 9 – COGNITIVE FUNCTIONS
Lateralisation of function
- The human brain is asymmetrical
oDivided into left and right hemispheres
oEach has different functions
oEach controls the opposite side of the body, with some exceptions
- Division of labor between the two hemispheres is known as laterlisation
The left and right hemispheres
- Information is exchanged between hemispheres through
oThe corpus callosum
oAnterior commissure
oHippocampal commissure
- In most humans the left side is for language
oFunctions of the rights are more difficult to summarise
Visual connections to the hemispheres
- Each hemisphere of the brain gets input from the opposite half of the visual world
- Human vision
oLight from the right half of the visual field shines into the left half of both retinas
oLight from the let half of the visual field shines onto the right half of both retinas
oVis field is opp hemisphere activity
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Auditory connections to the hemispheres
- Each hemisphere pays more attention to the ear on the opposite side
oEach ear sends the information to both sides of the brain
oBrain areas must compare input from both ears
oBut responds most to contralateral hemisphere
oAllows for sound localization to compare time of arrival, etc
Split brain operation – epilepsy
- Damage to the corpus callosum prevents the hemispheres from exchanging information
oEpilepsy: condition characterized by repeated episodes of excessive synchronized
neural activity (1-2% of people)
oAntiepileptic drugs
oRemoving focus
Where the activity starts
Good if there is only one focus, but bad if there are a few
Hard if in a bad spot
Damage to area – behavioural changes?
oCut the corpus callosum
Split brain people have undergone surgery to the corpus callosum
Can reduce prevalence of seizures
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- Behavioural difference for split brain people
oBecause the left side of the brain is dominant for language in most people, most
people
Have difficulty naming objects briefly viewed in the eft visual field
Present one visual stimulus to right visual field
Picked up y LH
Can verbally indicate you’ve seem the stimulus
If to left visual field
Can say you’ve seen it
Anterior and hippocampal commissures
- A small amount of info can still be transferred via several smaller commisssures
oDeficits can still continue after the operation because of these routes between
hemispheres
Split hemispheres: connection and cooperation
- Immediately after surgery, the brain hemispheres are often in conflict
- The hemispheres show differences of opinion
oEg; self portrait seen in right visual field correctly identified, but not when seen in
left visual field
Split hemispheres: competition and cooperation
- Gazzinga 00’ proposed the concept of the left brain as the interpreter
oTendency to invent and defend explanations for actions
Even when true causes are unconscious
- sides don’t know what the other is doing
The right hemispheres
- right hemispheres: more adept at comprehending spatial relationships
- helps see the big picture
opatterns, language comprehension and emotion
- damage to the right hemisphere causes difficulty perceiving others emotions, failure to
understand humor and sarcasm and a monotone voice
Inactivated left and right hemispheres
- brain surgery patients with the left hemisphere inactivated cannot speak
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Document Summary
The human brain is asymmetrical: divided into left and right hemispheres, each has different functions, each controls the opposite side of the body, with some exceptions. Division of labor between the two hemispheres is known as laterlisation. Information is exchanged between hemispheres through: the corpus callosum, anterior commissure, hippocampal commissure. In most humans the left side is for language: functions of the rights are more difficult to summarise. Each hemisphere of the brain gets input from the opposite half of the visual world. Damage to the corpus callosum prevents the hemispheres from exchanging information: epilepsy: condition characterized by repeated episodes of excessive synchronized neural activity (1-2% of people, antiepileptic drugs, removing focus. Good if there is only one focus, but bad if there are a few. Damage to area behavioural changes: cut the corpus callosum. Split brain people have undergone surgery to the corpus callosum.
