Nervous System

∞ generated and posted on 2016.01.18 ∞

Making up the central nervous system are the brain and spinal cord while in close association are the special senses.

The nervous system traditionally is divided into everything but the spinal cord and brain versus all of the nervous system, except the spinal cord and the brain. The spinal cord and the brain are described as the central nervous system and everything else the peripheral nervous system. Found in close association with the central nervous system but nonetheless somewhat outside of the central nervous system are what are known as the special senses.

Most of the human brain's high-level functions arise from the six layers of nerve cells and their dendrites embedded in its enormous surface area, called the cerebral cortex, which is compressed to a size small enough to be carried around on our shoulders through a process known as gyrification—essentially, producing lots of folds. Some regions of the brain are highly specialized, receiving sensory information from our eyes, ears, skin, mouth, or nose, or controlling our movements. We call these regions the primary visual, auditory, sensory, and motor cortices. They collect information from the world around us and execute our actions. But we would be helpless, and effectively nonhuman, if our brains consisted only of these regions.

In fact, the most extensively developed regions in the human brain are known as association cortices. These regions help us interpret and make use of the specialized information collected by the primary visual, auditory, sensory, and motor regions. For example, as you read these words on a page or a screen, they register as black lines on a white background in your primary visual cortex. If the process stopped at that point, you wouldn't be reading at all. To read, your brain, through miraculously complex processes that scientists are still figuring out, needs to forward those black letters on to association-cortex regions such as the angular gyrus, so that meaning is attached to them; and then on to language-association regions in the temporal lobes, so that the words are connected not only to one another but also to their associated memories and given richer meanings. These associated memories and meanings constitute a "verbal lexicon," which can be accessed for reading, speaking, listening, and writing. Each person's lexicon is a bit different, even if the words themselves are the same, because each person has different associated memories and meanings. One difference between a great writer like Shakespeare and, say, the typical stockbroker is the size and richness of the verbal lexicon in his or her temporal association cortices, as well as the complexity of the cortices' connections with other association regions in the frontal and parietal lobes.

Nancy C. Andreasen, 2014, from Secrets of the Creative Brain

The above video provides an introduction to the brain and its functioning, all to a degree from the perspective of psychology.

Nice, fast overview of what memories are and, in particular, how they form.