Developmental psychology.pdf

100 The Human Organism
receptors throughout the body. In a patient whose cortex has been exposed prior to
brain surgery, electrical stimulation of this area is often followed by such statements
as "My hand feels warm" or "I can feel my leg moving," even though these limbs have
not been stimulated (Penfield, 1958).
Again, the body is represented in an inverted sequence. The lower part of the
body is represented near the top of the brain, the trunk in the middle, and the upper
body toward the bottom of the cortex.
Our other senses apparently do not have such clearly represented locations.
Even pain is not well localized. Surgeons have cut into every part of the cortex without
producing any pain except that involved in penetrating the covering tissues. Possibly,
pain is mediated at the subcortical levels of the brain.
Association Areas
As emphasized already, the projection areas are not the exclusive seat of any movement
or experience. No complex human reaction is completely controlled by any one area
of the cerebral cortex or nervous system. Rather, each area is a center of neural activity
when a particular function is taking place. Control is inevitably shared by structures
in other areas, including the association areas.
Integrating Information Occupying large sections of the human brain around the
motor and sensory areas are the association areas, so called because they seem to be
involved in the integration of information. Data are brought together and presumably
analyzed here, although of course information is stored in diverse parts of the brain.
Not surprisingly, the association areas seem most significantly involved in memory,
language, and other complex mental processes.
The association areas, rather than receiving information directly from the sense
organs, obtain information from elsewhere in the brain. They process this stored information
and also the relationships between stored information and new stimulation.
Thus reactions in the association areas are significantly influenced by prior learning.
It is noteworthy that the association areas, specialized for the management of
higher-level thought, increase enormously in size as one ascends the phylogenetic scale.
The rat and cat, for example, have relatively little association cortex in comparison to
the motor and sensory projection areas, whereas in human beings we find the reverse
situation (Thompson, 1975).
'Fifteen years ago, while diving
from a 13 meter board, I struck the
bottom of the pool and it caused a
concussion which later left me with
the inability to say certain words.
Each attempt was an agony, for
when I could not say what I wanted
to I felt a strain and the desire to
hide my feelings.
The very next year, while
checking into a hotel, I was hit over
the head by a lead pipe wielded by
two young marine service
personnel during a robbery of my
rings and money. The blow relieved
pressure on my skull, which in turn
brought back my speech. Also, it
restored almost all the hearing in
my right ear, which I had lost in an
earlier accident. The doctors said
that pressure had built up on the
brain which had literally caused
both impairments.
Association Malfunctions The significance of the association area for touch can
be illustrated by reference to a disease known as astereognosis, literally meaning
"without tactual knowledge of space." If you were blindfolded and asked to handle a
small cube, you would have no difficulty identifying this object, but if you subsequently
suffered a serious impairment of the association areas for touch, you would be unable
to recognize it by touch alone. Loss of the association tissue causes impressions of touch
to lose the meaning they once had for you. Differences in sharpness and smoothness
could be experienced, assuming the sensory areas remained intact, I at they could not
be identified.
When such disorders involve language functions, we speak of aphasia, meaning
"without language." The visual impressions reaching your eyes from this printed
page have meaning only because relevant association areas retain what you have learned
previously about the significance of these characters. When the visual association area
is seriously disturbed, the corresponding functions are impaired. The disturbance may
be so serious that although someone sees written words and can even trace them, a
formerly literate individual does not understand what they mean.*
In concluding this section, we should note also that scientific knowledge is selfcorrecting.
There are almost always revisions. That is the nature of scientific inquiry,
and today there are exceptions to the three-way division of the cortex just enumerated.