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Lecture 3

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Life Sciences
Ramesh Balasubramaniam

Lecture 3 September-11-12 4:32 PM  Deafferentation & Neuropathy o Only afferent pathway sare affected  Caused by accidents/diabeetes  IW  Infected by a virus  All sensory fibres below neck were damaged by virus  Was rehabilitated  At first couldn't get out of bed  GL  Still confined to a wheelchair  IW were able to teach himself using sensory substitution and his deafferentation was a few inches below GL = better prognosis  Four lobes o Frontal - reasoning, planning, complex actions (coarticulation for e.g.) o Motor cortex at back of frontal lobe o Central sulcus - between frontal lobe and parietal lobe o On opposite side of central sulcus lies sensory cortex and rest of parietal lobe o Parietal lobe - handles skin based proprioceptive information o Temporal loe - memory, speech, hearing  Great Canadian Discovery o Motor cortex  End of frontal lobe right before central sulcus  Organization reveals a map of the body - somatotopic map  Docteur Penfield - canadian  1950's montreal  Surgery for people with epilepsy  Electrically stimulated parts of the cortex to see what would happen - observed the twitches and made a map  This was the discovery of the corticospinal tract  There was not an equal amt of space dedicated to all parts of the body o If we drew a human based on the size of the area of motor cortex based on the body parts = humunculus o Some parts of body have much larger representations - e.g. Hands o Dexterity is possible because hands have very large part of cortical real estate o We are the only mammal who has the power of speech o Pt who have lost a limb:  e.g. Phantom limb pain Limb is gone but sensation is still available becasue of intact cortex, can be switched  over eventually  There are pt who have overlapping somatic representations  Supranumery limbs  Digital representations of map would have to be divided between for example 6 fingers  Sometimes completely flips over  Spontaneous orgasms when pressed on pedal of the car  Genital and foot areas are very close  Image of Lou Gehrig and Stephen Hawking o What is common?  Both do not have problems with their cortex  Als o Affects motorneurons of the brainstem and spinal cord are destroyed and their target muscles wither away o All muscles have afferent and efferent connections to/from cortex o Tracts go down through brainstem and spinal cord - have alpha motor neurons synapsing onto muscle o Not completely atrophied but target muscles wither away o Patient retains cognitive function  Neuromuscular disease
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