Rewiring cortex: The role of patterned activity in development and plasticity of neocortical circuits

Visually driven activity is not required for the establishment of ocular do minance columns, orientation columns, and long-range horizontal connections in visual cortex, although spontaneous activity appears to be necessary. T he role of activity may be instructive or simply permissive; evidence for a n instructive role requires inquiry into the role of the pattern of activit y in shaping cortical circuits. The few experiments that have probed the ro le of patterned activity include the effects of artificial strabismus, arti ficial stimulation of the optic nerve, and rewiring visual projections from the retina to the auditory thalamus and cortex, These experiments demonstr ate that patterned activity is vital for the maintenance of thalamocortical , local intracortical, and long-range horizontal connections in cortex. (C) 1999 John Wiley & Sons, Inc.