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What is consciousness? Page 3a. |
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3 A. Cerebral Cortex. |
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From the Evolutionary perspective, the region of the brain which is the most recently developed. The cortex has three major functional regions: sensory cortex, the region which receives input from the various senses and which begins to integrate this information; association cortex, which processes this information and forms associations between the units of information (eg., associates the word chocolate with the colour brown) and motor cortex, where the brain controls various movement functions. Information is processed through the sensory cortex, to the association cortex and then to the motor cortex.For example, if I am walking down the street and see a great big gorilla bearing down on me with a large club, the information is taken into my sensory cortex and translated into "gorilla" and "club" in association areas, passed through various sub-cortical regions which add a fear component and finally the information is sent to my motor cortex, whereupon my legs start moving, preferably in the opposite direction to the gorilla's bearing. In fact, movement is probably processed to some extent by the caudate-striatum, and by the cerebellum. Attentional and control of the thought processes may involve thalamic and midbrain regions. And of course, all of this happens in the space of a second or two! |
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– The Temporal Lobe. |
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The temporal lobe is a region of the brain that is important in the formation and storage of long term memory. Damage to the temporal lobe can have profound effects on memory. Perhaps the most famous case involved a patient known in the literature as H.M., a man who underwent bilateral removal of part of the temporal lobe for the treatment of life-threatening epilepsy. As a consequence of this radical surgery, this patient retained his childhood memories, but he lost recent memories. Perhaps more importantly, he lost the ability to remember anything new, ie. to convert short-term memories into long-term memories. Thus H.M. lived in a world of several minutes duration. He was convinced that he had just woken up and that the writings in his diary were written by someone else pretending to be him.
The earliest forms of Alzheimer's disease involve damage to the transentorhinal cortex, a region of the temporal lobe. The temporal cortex is most profoundly affected in Alzheimer's disease, hence the severe memory deficits. |
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