The Great Divide: Right and
Left Hemispheres
1)
Holistic or Analytical
a)
Left brain:
analytical, logical, precise, and time-sensitive
b)
Right brain:
processes holistically rather than breaking things down into parts, more
involved in sensory perception than abstract thinking. More emotional than the left. Cf. patient responses to right brain damage
as compared to left.
2)
White and grey
matter: cell bodies and bundles of axon
a)
The right brain
has more white matter, left more grey:
i)
Right’s longer
axons means left-brain connections to neurons that are farther away – broad,
multifaceted thinking, vaguer.
ii)
Left brain draws
on more brain modules at the same time – densely woven, more intense and
detailed thinking
b)
Like An old
married couple: one takes the dominant role, executive, day to day business
most of the time, the other uses his/her particular talents to sense of the
environment. One keeps the other informed.
c)
What registers in
one hemisphere registers in the other, but less fully.
3)
Incomplete
hemispheric communications result in experiences of half knowledge:
a)
“Something awful
has happened but it hasn’t hit me yet” (left brain acknowledges something but
right hasn’t taken it in)
b)
“There’s
something I don’t like about this but I can’t put my finger on it” (left brain
(right brain grasps but left is only faintly aware)
c)
Rationalizing our
actions: left brain processes that covers for the fact that our decisions were
motivated largely by the emotional right brain
4)
Splitting the
Brain
a)
Severing the
connections by severing the corpus callosum
and the anterior commissure (which
connects the subcortical regions of the brain known as the limbic system)
i)
Normally, conscious
stimuli is sent down from the cortex to the limbic system, evokes a response if
significant (fear, anger), fed back to the cerebral hemispheres where it is
processed into complex feelings.
b)
In split-brain
patients, the normal and sophisticated processing back and forth is stopped.
Twin-towered building connected only by an underground walkway (the anterior commissure).
i)
The case of V.P.: pp. 42, pp. 47-48 Passing of
emotional stimuli between hemispheres is blocked in split brain patients.
ii)
Alien hands:
in patients who have suffered damage to one or both brain areas, in split-brain
patients. Living in two minds. Left brain may not always wrest physical
control by passing inhibitory messages. pp. 48, 49