External and endogenous phenomena are detected by sensors. Most of them
are just modified neurons. Some others (in human retina, in ears) are hypersensitive
cells. Sensorial data are processed in the brain which send orders to the muscles. From
the signals of a great number of olfactory receptors, brain extracts the ordered list of the
six more strongly excited. Man can learn to recognize 2 103 smells (and dog 106). Eyes
of bees or frogs have poor keenness sensitivity. Human’s retina has very large keenness
and sensitivity. In frog, visual signals are processed on the retina. In man, they are sent
to the brain and processed by several parallel paths. Adaptable software governs inborn
or learned behaviors (for instance walking). Only one out of several competitive
behaviors (for instance the various possible directions of eyes) has to be chosen.
Choosing centers (for instance superior colliculus) select the more strongly excited
among several competitive instinctive drives, which are sophisticated combinations of
several sensorial signals. Behaviors control the muscular activity. They are simple
automatisms in frogs. In men, they consist in layers of control devices. The lower-level
unit is based on two antagonist muscles and their embedded sensors. This unit governs
muscular tonus. The cerebellum is in charge of the phasic excitations. Various signals
combine to build a representation of the body position.
Keywords: Behaviors, body representation, cerebellum, choices, colliculus,
competitive instincts, eye, hearing, instinctive drives, muscular embedded sensors,
muscular tonus, optical coding, phasic excitations, pleasure impulse, retina, sense
of smell, sensors, striated muscles, thirst control, visual pathways.
