J Neurophysiol (November 1, 2002). 10.1152/jn.00591.2002
Submitted on 23 July 2002
Accepted on 24 July 2002

Hippocampus Retains the Periodicity of Gamma Stimulation In Vivo

 ¹A. I. Virtanen Institute and  ²Department of Computer Science and Applied Mathematics, University of Kuopio, FIN-70211 Kuopio, Finland; and  ³Department of Psychology, University of Connecticut, Storrs, Connecticut 06268

Mikkonen, J. E., T. Grönfors, J. J. Chrobak, and M. Penttonen. Hippocampus Retains the Periodicity of Gamma Stimulation In Vivo. J. Neurophysiol. 88: 2349-2354, 2002. Several behavioral state dependent oscillatory rhythms have been identified in the brain. Of these neuronal rhythms, gamma (20-70 Hz) oscillations are prominent in the activated brain and are associated with various behavioral functions ranging from sensory binding to memory. Hippocampal gamma oscillations represent a widely studied band of frequencies co-occurring with information acquisition. However, induction of specific gamma frequencies within the hippocampal neuronal network has not been satisfactorily established. Using both in vivo intracellular and extracellular recordings from anesthetized rats, we show that hippocampal CA1 pyramidal cells can discharge at frequencies determined by the preceding gamma stimulation, provided that the gamma is introduced in theta cycles, as occurs in vivo. The dynamic short-term alterations in the oscillatory discharge described in this paper may serve as a coding mechanism in cortical neuronal networks.