The human brain has an average of 86 billion…

Page 32 keyword thought The human brain has an average of 86 billion neurons. 69 billion of them are located in the cerebellum which is the small structure at the back of the brain that helps refine motor control. The entire cortex which is the area that we think is responsible for human thought and culture has only 17 billion, and the rest of the brain has a little less than 1 billion. The frontal lobes and prefrontal cortex which are the part of the human brain that's involved with memory and planning, cognitive flexibility, abstract thinking, initiating appropriate behavior and inhibiting inappropriate behavior, learning roles, picking out relevant information perceived through the senses, - - have vastly fewer neurons than the number in the visual areas, the other sensory areas, and the motor areas of the cortex. What is larger in the frontal lobes than the rest of the brain however is the arborization of the neurons, that branching of the dendric tips of the neurons with the resulting possibility of increased connections. When brain size increases, what is increasing is the number of neurons, their connections and the space between the neurons. The finding that the human cerebral cortex volume is 2.75 * larger than a chimpanzees, but has only 1.25 times more neurons intimates that a good deal of the increased mass is due to the space between the cell bodies and what that space is filled with. The space, known as neuropil, is filled with the stuff that connections are made of which are axons, dendrites and, and synapses. In general the larger the area, the better connected it is, is more neurons connect to more and more other neurons. As the brain of scaled up however if every neuron were to connect with every other neuron the increased volume of connections and the increased length of connection stretching across the increasing size would slow down nerve signal processing speed and the overall benefit would be trivial. What happens is that not every neuron is connected to every other neuron. There's a fall and percentage of connectedness. At some point there's absolute brain size and total when you're on number increases, the proportional connectivity decreases and the internal structure changes as the connectivity pattern changes. In order to add new function, the decrease in proportional connectivity forces the brain to specialize. special local circuits, made of an interconnected group of neurons, are created to perform specific processing jobs and become automatic. The result of their processing is passed on to another part of the brain but all the computations that were used to arrive at the result are not. So as we discussed with the visual discussion perception problem, the result of the processing which is the judgment that the gray square appears lighter or darker is passed on, but the processing steps that arrived at that conclusion are not. This is critical in the forming of new habits and you automatic actions that the brain can take.

— from The Instruments (Awareness/Perception/Expectations)

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