Physiological learning theory.

Attention or "concentration" requires control of activity in those excess neurons that are not necessary for the present task. The control is probably not a massive inhibitory suppression but may be a recruiting process, a function of complex perceptual and associative learning that begins with early experience. Inhibition, however, may still be of crucial importance as a sharpener of associative mechanisms, and the child with minimal brain damage may have suffered a selective loss of inhibitory neurons.