The Cerebrum Or Forebrain





For convenience the various lobes of the cerebrum are known as frontal,

temporal, parietal, and occipital, according to the parts of the brain

referred to: as forehead, temples, crown, or occiput. The cerebellum, or

hind brain, is also divided into two hemispheres, and is situated behind

and below the hemispheres of the cerebrum.



A system of localization has been roughly mapped out, the result of

careful laboratory work on animals and of studying the loss of various

functions in human beings as related to the location of brain injuries.



From these experiments it seems proved that consciousness belongs only

to the cortex or surface of the upper brain, and that the vast realm of

the unconscious belongs to the lower brain centers. Hence the cortex is

the organ of consciousness, and the lower centers are the repository of

the unconscious until it again becomes conscious.



The motor zone of the cortex we now know to be situated in the

convolutions bordering the fissure of Rolando. Vision is evidently

excited from the occipital lobes, though not yet conclusively proved.

Smell, presumably, is located in the temporal lobes. Considered action

is directed from the upper hemispheres only. It is significant that the

hemispheres of the cerebrum are also accepted as the seat of memory for

man--that intellectual quality which makes him capable of acting from

absent stimuli, stimuli only present to memory; which makes it possible

for him to reason the present from the experiences of the past.



But in all animal life, except the higher forms, the control of action

is from the lower brain centers, centers which respond only to present

objects. With them memory, as man knows it, is lacking; but the

reactions of the past are indelibly imprinted upon motor nerves and

muscles, so that when the present object presses the button, as it

were, calling forth the experience of the race, the animal instinctively

reacts.



But of what use to man, then, are the lower brain centers?



In man, as in lower animals, they care for the vegetative functions of

life, so that our blood continues to circulate, the air enters and

leaves our lungs, digestion is carried on, with no assistance from the

upper centers, the hemispheres of the cerebrum being thus left free for

concentration on the external world of matter, which it can transform

into a world of thought.



It is the lower or vegetative brain that may still exist and keep life

intact when the functions of the cerebrum are destroyed. We can say,

then, of the brain as a whole that it is the organ of the mind, the

sine qua non of the mind, the apparatus for the registration of sense

impressions. The senses themselves are the rudiments of mind, are the

means by which stimuli alighting on sense organs enter consciousness;

for the nerves of special sense immediately carry the impetus to the

brain, where it is recognized as the "not me," the something

definitely affecting the me, and demanding reaction from the me.



The functions of the cerebrum we find grouping themselves in three

classes: intellect, emotion, and volition, more simply, thinking,

feeling, and willing; and we find no mental activity of the normal or

abnormal mind which will not fall into one of these groupings. This

does not mean that one part of the brain thinks, another part wills,

another part feels; for in the performance of any one of these functions

the mind acts as a whole. Our thinking or our willing may be permeated

with feeling, but the entire mind is simply reacting simultaneously upon

various stimuli.





The Central And Peripheral Nervous Systems In Action The Deluded Patient facebooktwittergoogle_plusredditpinterestlinkedinmail

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