Developmental changes in trial-to-trial variations in whisker barrel responses studied using intrinsic optical imaging: Comparison between normal andde-whiskered rats

We used an intrinsic optical imaging technique to examine postnatal develop mental changes in the rat barrel response to a single whisker movement. We compared the optical response patterns between control and de-whiskered rat s, from which whiskers were removed except for the D1 whisker just after bi rth. Barrel responses were evoked by D1-whisker movement stimulation, and t he intrinsic optical signals were detected from the somatosensory cortex th rough the dura mater. In the control rats, the area of the barrel response decreased gradually as postnatal development proceeded from 2 to 7 wk, unti l reaching the adult pattern. On the other hand, in the de-whiskered rats, the barrel response area did not change during development and showed a lar ger size than in the control rats. We also compared the trial-to-trial vari ations in the barrel responses between the two groups. In the control rats, trial-to-trial variations in the optical responses were observed under the same conditions of whisker stimulation, and the extent of the variations d ecreased with postnatal development up to 7 wk. In the de-whiskered rats, t rial-to-trial variations were also observed, but the extent was larger and unchanged during development. In both groups, the positions of the response area were the same with respect to the bregma. These results suggest that the decrease in the area and variations in the optical responses are caused by interactions of the corresponding whisker barrel with neighboring barre ls and that these interactions are necessary for the developmental stabiliz ation of the intracortical horizontal connections, which are widespread and have high plasticity in early postnatal periods.