TEMPORAL sequences of inputs to the rat whiskers are thought to be important to recognize the environment of the rat. In this study, we applied combined stimulations to neighboring whiskers D1 and D2, and the cortical activities evoked in the rat barrel cortex were measured using the intrinsic optical imaging technique. The timing of stimulation to neighboring whiskers affected the evoked cortical activities: the cortical activity evoked by in-phase stimulation to D1 and D2 was significantly stronger than that evoked by out-of-phase stimulation. In order to elucidate the mechanism underlying this phenomenon, the effect of blockade of cortical inhibitory circuits was examined. Iontophoretic application of bicuculline or saclofen (GABA-A or GABA-B antagonist) increased the evoked cortical activities and diminished the difference in activities obtained with in-phase and anti-phase stimulation. These results suggest that local inhibitory circuits play a critical role in coding temporal information of whisker stimulation.
1PRESTO, JST, Japan
2Laboratory for Neural Modeling, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
3Department of Physics, Waseda University Tokyo, Japan
4Department of Physiology, University of Tokyo School of Medicine, Tokyo, Japan
5Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN, USA.
6Corresponding Author and Address: Ayako Ajima, Laboratory for Neural Modeling, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
ACKNOWLEDGEMENTS: We thank Dr R.T. Kado for his technical support to make whisker stimulators and for his critical comments.
Received 12 April 1999; accepted 2 May 1999