Lateralized effects of monocular training on dendritic branching in adult split-brain rats

A number of experimental approaches have indicated differential interneuronal connectivity following differential experience during both development and adulthood. In Golgi preparations, prolonged maze training was reported to alter dendritic branching of distal apical dendrites of Layer IV and V pyramidal neurons in adult rat occipital cortex. To determine the specificity of this effect to direct involvement in the visual aspects of training, the effects of monocular maze training, using a split-brain procedure and opaque contact occluders, was examined in the present study. Rats were maze trained with unilateral or alternating monocular occlusion, while nontrained rats with unilateral or alternating monocular occlusion were handled briefly and given water reward. There was no within-animal effect of fixed occluder position in non-trained controls. In unilaterally-occluded trained rats, Layer V pyramidal neurons in occipital cortex opposite the open eye had greater oblique dendritic length in the distal region of the apical dendrite than did those opposite the occluded eye. Similarly, rats trained with alternating occlusion had greater distal apical oblique dendritic length in Layer V occipital pyramidal neurons than did nontrained controls. This indicates that morphological sequelae of training are concentrated in areas processing information associated with visual aspects of the training and renders unlikely general metabolic or hormonal causation of such effects.