Chapter 1: “The Phantom Within”
Modularity vs. Holism
Modularity – different parts of the brain are highly specialized for mental capabilities. (i.e., FFA, module for language, and etc…) Holism – “connectionism”; many areas, especially cortical regions, can be recruited for multiple tasks. *** Ramachandran believes these two views are not mutually exclusive. The brain is a dynamic structure that employs both “modules: in a marvelously complex interplay. (uses Baywatch as an analogy, saying localization is not a bad place to start, so long as we avoid the pitfall of thinking that it holds all the answers. (how instead of where)
Smiling at a good friend vs Smiling in front of a camera
Smiling at a good friend
Visual message of friend’s face -> limbic system (brain’s emotional center) -> basal ganglia orchestrate the sequences of facial muscle activity needed for producing a normal smile. Smiling in front of a camera
Processed through the auditory cortex and language centers -> motor cortex (specialized in producing voluntary skilled movements)
H.M – had hippocampus removed due to a particularly intractable form of epilepsy Could not form new memories, yet he could recall everything that happened before the operation. Illustrates the power of modular approach
Bill – angular gyrus damaged due to stroke injury (dyscalculia) This region somehow necessary for numerical computational tasks but is not need for other abilities such as STM, language or humor. People with dyscalculia also have an associated brain disorder called finger agnosia: They can no longer name which finger the neurologist is pointing to or touching.
Chapter 2: “Knowing Where to Scratch”
Tom Sorenson – lost his arm in a car accident; phantom arm Phantom limb – an arm or leg that lingers indefinitely in the minds of patients long after it has been lost in an accident or removed by a surgeon (some patients also experience phantom breasts, phantom erections, phantom face/nose, phantom appendixes and phantom menstral cramps). Some patients experience excruciating pain in the phantom arm, hand or fingers, so much so that they contemplate suicide. (pain is unrelenting and untreatable) First coined by physician Silas Weir Mitchell after the Civil War. Theory 1: phantom limbs are merely the result of wishful thinking; similar to recurring dreams (utter nonsense) Theory 2: frayed and curled-up nerve endings in the stump that originally supplied the hand tend to become inflamed and irritated, thereby fooling higher brain centers into thinking that the missing limb is still there.
An artist’s whimsical depiction of the manner in which different points on the body surface are mapped onto the surface of the brain. Tim Pons et al. found that when they touched the monkey’s face, the cells in the brain corresponding to the “dead” hand started firing vigorously. ***This meant that you COULD change the body map on the surface of the brain. Used magnetoencephalography (MEG), which relies on the principle that if you touch different body parts, the localized electrical activity evoked in the Penfield map can be measured as changes in magnetic fields on the scalp (noninvasive) Showed that brain maps can change, sometimes with astonishing rapidity. Nerves that once supplied the hand begin to innervate the stump and these frayed nerve endings form little clumps of scar tissue called neuromas, which can be painful. When neuromas are irritated, they send back impulses to the original hand area in the brain, fooling the brain that the hand is still there; hence the phantom limb and the notion that the accompanying pain arises because the neuromas are painful.
When we think of sensations arising from the skin we usually only think of touch. Distinct neural pathways that mediate sensation of warmth, cold and pain also originate on the skin surface. Placed a drop of warm water on Tom’s face
Felt it trickling down his face and...
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