Section X. MISCELLANEOUS TOPICS
12-36. CEREBRAL AREAS
Specific areas of the cerebral cortex are concerned with specific parts of the
body, with specific types of inputs, and with specific types of activities. Most often, each
area is numbered as a specific Brodmann's area. For example, the precentral gyrus,
concerned with volitional motions, is Brodmann's area number 4. It is the beginning of
the pyramidal motor system. Likewise, the superior temporal gyrus (at the inferior
margin of the lateral sulcus) is Brodmann's area number 41; it is the center for hearing.
a. About 90% of humans are right-handed. Thus, for these individuals, the left
cerebral hemisphere is said to be dominant over the right cerebral hemisphere.
b. For 96% of humans, the speech center is located in the left cerebral
c. Thus, an injury to the left cerebral hemisphere is generally more serious than
an injury to the right cerebral hemisphere.
a. Memory is that faculty which enables an individual to store and retrieve
factual items (sensations, impressions, facts, and ideas). Memory is ultimately the
result of the unceasing flow of sensory information into the CNS. These items are
stored in the CNS; just exactly how and where is the subject of much research and
discussion. All sensory inputs are collated against these stored items in order to arrive
at an appropriate action decision. (Often, no action is the most appropriate decision.)
b. At present, at least two types of memory are recognized in the human
brain--short-term memory and long-term memory.
(1) Short-term memory. A common example of short-term memory is the
ability to hold a phone number in mind for a number of seconds without "memorizing" it.
Short-term memory is usually limited to about seven bits of information.
(2) Long-term memory. A portion of the cerebral cortex known as the
hippocampus is thought to be important in transferring information from short-term
memory to long-term memory. If the hippocampus is nonfunctional, the individual can
learn nothing, but his previously long-term memory remains intact.