Early experience effect on dendritic branching in normally reared kittens

Abstract The neural modifications induced in somatosensory cortex by a simple avoidance procedure in developing kittens were studied by mapping receptive fields of single cells on the skin, thereby building a body map and measuring branching patterns of dendrites of stellate and pyramidal cells. Kittens were trained daily to tasks in which they had to maintain flexion of one of the forelegs to avoid a mild shock on the dorsal aspect of the forearm. Training took place during the 4th through 10th week of life. Recordings from single cells in somatosensory cortex were used to define peripheral receptive field types and sizes and also to construct a representational map of the body with special attention to that part dedicated to the forearm. Results indicate that the representation of the trained forearm was much larger than the untrained one. Golgi Cox techniques were used to examine the effects of the training procedure on branching patterns of dendrites. We found an increase in approximately 30% of the number of dendritic intersections, indicating a generally enhanced growth of the dendritic trees in the cortex corresponding to the enlarged representation. An ordering analysis revealed that much of the growth was concentrated in the basal dendrites. As previous studies showed that the effects of early experience are permanent, we have every reason to believe that apparently minor early experiences may have lasting effects on adult behavior.