CHAPTER 4.docx

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26 Apr 2012
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CHAPTER 4
The observations of functional specialization of the brain led to the development of modern
neuropsychology
Laterality: the functional specialization of the right and left hemispheres
Left hemisphere (LH) is specialized for language and the control of the right hand and fingers
Right hemisphere (RH) played a role in visual identification of objects, is specialized for music,
emotion, and spatial abilities as well as control of the left hand and fingers
RH has poor linguistics, therefore took longer to understand its functions
Split Brain
- RH and LH communicate with each other using commissural systems: anterior and posterior
commissures, the corpus callosum, and the habenular commissure and the hippocampal
commissure
- Roger Sperry and Ronald Myers: cat experiment using commissurized and non-commissurized
cats. A stimulus shown to the right and left eye separately and a response was to be made to
acquire the reward. In commissurized cats, there was no transfer of learning between the eyes
a stimulus shown to the right eye, was not recognized by the left eye and had to be trained
separately
~ WHY?
~ When corpus callosum severed, information that is received from the right visual cortex
can no longer be integrated with that of the right visual cortex
~ Information received by one hemisphere can no longer influence the other hemisphere
- Sperry and Myers suggested that the severing of the commissures would improve the prognosis
for individuals with epilepsy
- Individuals who have had a commissurotomy have two hemispheres that are intact but separate
- Michael Gazzangiga and Sperry, observed that the RH was capable of comprehending spoken
and written words, capable of arranging letters to spell three or four letter words
- Levy used two different halves of faces that were combined to make one face (chimeric) when
the picture was shown to the individuals with a split brain, the two hemispheres “saw” different
faces (most were not aware that two faces were present) most of the time, the participants
picked the face that appeared in the left visual field (which sends info to the RH)
Intracarotid Amobarbital Testing (IAT)
- IAT is also known as the Wada test
- IAT is commonly used to assess the laterality of language in individuals who will be undergoing
brain surgery
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