The Hidden Face of God by Gerald L. Schroeder

Author:Gerald L. Schroeder
Language: eng
Format: epub
Publisher: Simon & Schuster
Published: 2001-06-24T00:00:00+00:00

Figure 8

Visual Pathways Within the Brain

Note that the signals from the right sides of the retinas of both eyes go to the right hemisphere of the brain. Signals from the left sides of the retinas go to the left brain hemisphere. The amygdala, being closer to the eyes than the visual cortex, receives the signal before the visual cortex and can react to that information even though the amygdala produces no conscious visual awareness.

All incoming senses, other than smell, are inverted the way sight is and all have the thalamus as the first station. The neural circuitry of the thalamus tackles an intense amount of book-keeping since all the inputs are identical electrochemical pulses. Best not to mix auditory with retinal signals, or you’ll be hearing sight and seeing sound. Smell, a most basic of senses, bypasses the thalamus and is routed directly to the amygdala.

It is the amygdala, one of a group of organs at times collectively referred to as the limbic system, that evokes emotional memory even when at times that memory evades our logic. During a recent fall semester, a student confided to me that he wasn’t able to concentrate while sitting next to a particular member of the class. He could not understand why. A bit of questioning revealed that the aftershave lotion used by the other man was the one he had favored during a previous summer’s escapade. It evoked in him all sorts of bittersweet feelings he had been unable to explain.

While all vertebrates have the emotion-packed limbic system, only mammals have a highly developed cerebral cortex, the site of advanced logic and data processing. The wisdom of the cortex notwithstanding, the amygdala, because of its proximity to the thalamus, induces its response before the cortex can get into the act. The limbic system is the fast route. The cortex is still working on the data when the amygdala is screaming for action. From here arise the responses of fight and flight, and, interestingly, a third emotional choice not usually mentioned, submission. Depending upon one’s past experiences, the amygdala quickly chooses a response to incoming sensory information and prompts a response. The first part of us that acts, our first decision maker, is also our least logical self.

Even with the “slow” processing of the cortex, we’re talking about milliseconds. Slow is still quite fast. But the difference in timing is unfortunately sufficient to, at times, let us blurt out a response that moments later has us groaning “How could I have said that?”

This fast limbic response ability reveals an important aspect of physiology. The limbic system, and hence all vertebrates, including reptiles, birds, and fish, store emotional information as long-term memory. And against this stored information, incoming data are analyzed. Memory is not the province of mammals alone. All vertebrates house within their brains some aspects of their personal histories.

Having raised trout in my high school years from egg through release into New England streams and lakes, I have no question as to memory

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