Ireland Neurophysiology: Test 3

Terms in this set (71)

1. Early damage: uncontrollable seizures during the first year of life may lead to the removal of the damaged hemisphere (successful deals with seizures 70% of the time).
A. Left hemisphere removal: child is able to speak, write, and use language. Somehow, the right hemisphere develops these functions. However, the right hemisphere cannot assume its own functions. Something must be sacrificed (i.e. special organization). Also, some functions are completely lost, even if removal occurs very early and the L.H. is removed, the right side of the body would be paralyzed. However, early brain damage does show that the remaining hemisphere has flexibility or plasticity to develop.
B. Case study: at 5 and 1/2, left hemisphere removed (seizures). Tested at 27 to see which functions R.H. had assumed. Paralyzed on right side of body. No sensations on right side, and blind in right visual area (the R.H. does not assume sensory and motor functions found in the L.H.). Completed college.

2. Late damage: Either hemisphere can develop language functions until the ages of 5-7. After age 10, the brain damage then results in serious speech and language problems if the L.H. is damaged. At this point, the R.H. lacks the flexibility to assume these functions. Damage to the L.H. before 10 may result in:
A. Aphasia (complete): no speech.
B. Broca's Aphasia: slow and labored speech.
But the prospects of recovery are very good. After 10, the prospects for recovery are very poor.

3. Reorganization of sensory representations.
Considerable redundancy exists throughout the CNS so that even though there may be apparent recovery from brain damage, it is only because impaired behavior is mediated by alternative redundant, uninjured circuits. This may occur since during development, many axons for tentative connections with a given postsynaptic neuron (competitive process leads to activation of some, but not all). Upon injury, these previously ineffective axons may be activated as with compensatory mechanisms.