Chaotic stimulus dependent long-term potentiation in the hippocampal CA1 area

In our previous report [Tsukada, M., Aihara, T., Saito, H., Kato, H., 1996. Neural Netw. 9, 1357-1365], the temporal pattern sensitivity of long-term potentiation (LTP) in hippocampal CA1 neurons was estimated by using Markov chain stimuli (MS) with different values of the serial correlation coeffic ient rho (1) between successive interstimulus-intervals. In this paper, the effect of chaotic stimuli (CS) on induction of LTP in the hippocampal CA1 area was investigated in comparison with that of MS and periodic pattern st imuli (PS). The CS were produced by a modified Bernoulli map, so that inter stimulus sequences with various values of rho (1) can be generated by chang ing the parameter B. These stimuli had an identical first order statistics (mean interstimulus-interval), but their higher order statistics such as th e serial correlation coefficients were different. The LTP induced by CS at B = 2 was significantly larger in magnitude than that of PS and MS, and als o depended on the initial value of CS at B = 2 and 3. These results suggest that chaotic signals play an important role for memory coding in the hippo campal CA1 network. (C) 2000 Elsevier Science Ireland Ltd. All rights reser ved.