CHAPTER2EXXERCISE5_MYERS

Chapter 2

Question 5

What are the arguments and evidence that have been put forth to support the notion that there are two separate parts of the brain?

Argument 1: Functions of the brain are localized.

Evidence:

1. Damage to Broca's area, the inferior frontal gyrus of the left hemisphere, results in the inability to follow the rules of syntax and the production of agrammatic language.
2. Damage to Wernicke's area produces semantically incoherent language, for example trouble naming objects and producing lexical errors.
3. Deaf aphasics also show deficits in the same areas of the brain as hearing aphasics, even though they are signing rather than speaking.
4. Left hemisphere damaged Japanese are unable to read Kana, the sound system-based language, and right hemisphere damaged Japanese are unable to read Kanji, the ideographic-based language.

Argument 2: Brain imaging technology allows us to identify parts of the brain and their correlation to cognitive tasks.

Evidence:

1. Magnetic encephalography (MEG) allows us to measure activity of the living brain and its reaction to stimuli.
2. Comparisons of fMRI of brain lesion patients and PET scans of normal patients showed that the lesions in fMRI patients, who had specific linguistic deficits, corresponded exactly to the functioning areas in PET patients, who were able to perform the tasks that the fMRI patients could not.

Argument 3: The left hemisphere is predetermined to develop language in very young children.

Evidence:

1. Babies expressing language-like sounds open the right side of their mouths more than the left side, indicating greater activity in the left hemisphere, which controls movement of the right side of the body.
2. If the left brain has been removed the right brain will compensate for the missing brain functions, but children who undergo a right hemispherectomy before the age of two generally do not develop language.

Argument 4: The corpus callosum is the connection between the left and right hemispheres of the brain.

Evidence:

1. When the corpus callosum is surgically split, the two hemispheres cannot communicate. For example, when a patient is given an object in the left hand, he or she can sense the object but cannot describe it, because the information cannot be sent from the right hemisphere to the left, where the language cortex is located.
2. Split brain operations show that the two hemispheres have different strengths. The right hemisphere is more visually oriented: it is superior in pattern matching tasks, recognizing faces, and in spatial tasks. The left brain is more abstract in orientation: it is stronger in language, rhythmic perception, temporal-order judgments, and arithmetic calculations.

Argument 5: There are several experimental evidences of brain organization.

Evidence:

1. Dichotic listening allows researchers to study the effects of linguistic sounds and non-linguistic sounds on the brain and how the brain processes these sounds. Evidence shows that the left hemisphere processes linguistic sounds and the right hemisphere processes non-linguistic sounds, thus showing strong lateralization of the brain.
2. Event-related brain potentials (ERP) allow scientists to study how quickly the brain processes language and the area it is being processed in. It also shows how strongly the brain responds to the stimulus and the variations in timing, pattern, and amplitude of the evoked potentials.