Читать книгу Neurobiology For Dummies - Frank Amthor - Страница 30

The neocortex is one of the most important “inventions” of mammals. It dominates the mammalian brain in volume, particularly in primates. One of the most remarkable properties of the neocortex is that it has the same six-layered structure virtually everywhere, with the same cell types in what appears to be the same general minicolumn circuit. This is in stark contrast to the rest of the brain, where each area tends to have its own distinct set of cell types and neural circuits.

Mammals became the dominant land animals on earth after the demise of the dinosaurs about 65 million years ago. Some neurobiologists conjecture that mammals were able to rapidly diversify into all the niches abandoned by the extinction of the dinosaurs, as well as many new ones, by expanding the standard neocortex circuit for processing whatever visual, auditory, or fine motor acuity that niche demanded.

Neocortical processing power is primarily a function of area. Increased area in neocortex has two main uses:

 Increasing “acuity,” whereby, for example, a larger area can support a higher density of peripheral receptors, such as retinal ganglion cells in the fovea or mechanoreceptors in the fingertips.

 Increasing the number of processing stages in a hierarchy of “association” areas that are increasingly specific and powerful with respect to particular features. Examples are the fusiform face area that allows you to instantly identify thousands of faces that all have the same major features (eyes, nose, mouth) in the same relative positions.