Effects of early visual and complex stimulation on learning, brain biochemistry, and electrophysiology.

A complex stimulation regimen (visual, auditory, and somesthetic-kinesthetic with forced movements, 30 times for 30 min each within 14 days) increased significantly the amplitudes of visual cortical evoked potentials (EPs) in adult rats if applied during the second postnatal fortnight. The EP increase after stimulation during the first 14 days after birth was not significant. Visual stimulation alone was compared with complex stimulation (visual plus forced movements) during the 2nd postnatal fortnight. More specific local changes in the visual cortex were revealed in brain biochemistry (lower DNA concentration, more RNA and protein per cell) and cortical electrogenesis (enhanced visual EPs) after visual stimulation alone, whereas complex stimulation induced more diffuse changes and rather profoundly influenced higher nervous functions (viz., memory retrieval - improved 24-h). Involvement of both specific and nonspecific mechanisms in the aftereffects of early stimulation is indicated.