lecture 25: individuality Flashcards
an awareness of one’s own
existence
Consciousness
Consciousness
Consciousness includes awareness of one’s own
sensations, having one’s own
thoughts, awareness of one’s physical self and
one’s surroundings
Split Brain
2 minds in one skull following corpus
callosum section
Alien hand syndrome
limbs that have a mind of
their own after callosum lesions
Hemispatial neglect
parietal lobe strokes that
lead to body parts that no longer feel to patient as
if they are part of the body
Phantom Limbs
parts of the self that no longer
exist but for the patient won’t go away
Commisurotomy
(split brain) patients:
disconnected selves
A last resort measure
to help control severe
intractable epilepsy
* Studied by Roger
Sperry at Cal Tech
(shared Nobel with
Hubel and Wiesel,
1981)
* Nearly 200 million
axons cut!
What brain functions are
divided:Commisurotomy
All cross-talk between hemispheres
– Cut fiber systems that connect right and left
visual fields
* As a result the conscious perception of objects in
each hemisphere is now restricted only to the
information that came in via the half of the visual
field served by that hemisphere.
* The left hemisphere is aware only of things in the
right half of the visual field and the right
hemisphere is only aware of things in the left
visual field.
– Things felt with the right hand are only
perceived in the left hemisphere and vice
versa for things felt with the left hand
– Surgery cuts off the right hemisphere from
expressing itself with speech because the
main language centers are (most of the time)
in left hemisphere
Alien Hand Syndrome sometimes associated
with absence of callosal connections- parts that
have a mind of their own
- A week or two after brain bisection and also
associated with strokes and tumors of the
callosum: parts of the body become
autonomous uncontrollable in action. - Patient reports that these parts are a separate
person (sometimes a different gender than
the rest of the body)- a woman might call her
autonomous hand “he.” Another patient called
limb : “Baby Joseph
- Hemispatial neglect: Unawareness of the
existence of left space (including left body parts)
due to lesions in right hemisphere
If right brain damaged (typically parietal cortex)
then awareness of left half of the world is lacking.
Although on this one point not “rational,” the
patient is otherwise normal
* The verbal left hemisphere, which oversees right
space, is unaware of the existence of left space.
* The LH hemisphere sometimes resorts to verbal
confabulation to patch over the inconsistencies of
a world with no left space. For example patients
may deny ownership of their left hand
- Parts that wont
go away: Phantom
Limbs
After amputation of limbs, digits, or other surgical body part excisions,
the lost body parts are still sensed as being present. Although their size
might change (think of Novocaine injection in face).
This hallucination may be a result of the fact that the absence of body
part does not erase its memories in the brain.
In some cases (especially after a prolonged period of pain or immobility
of the limb prior to amputation), the phantom may be excruciatingly
painful. For example a patient may sense their phantom hand clenched
in a fist with its phantom nails digging into their phantom palm.
Because the limb is missing they cannot undo the clench and relieve the
pain
Traditional methods of anesthetizing the stump or more proximal nerve
cuts are totally unsuccessful (“chasing the phantom”)
Phantom Limb
therapy
A mirror box allows the patient to “see”
the phantom limb– and has
revolutionized the treatment of
phantom limb pain: perhaps by replacing
old memories with updates via
reconsolidation
List several pieces of evidence suggesting that our individual brains are actually a composite of systems that have somewhat different world views.
What are the principal differences between the skills associated with the left and right hemispheres?
