Precisely repeating spike temporal sequences in spontaneous activity of cultured hippocampal neuronal networks on multi-electrode arrays

Abstract

Neurons can respond to stimuli with temporally precise firing events and use precisely temporal spike patterns to encode information. However, whether or not such precise temporal spike sequences occur in the spontaneous firing activity of neuronal networks in vitro is not well understood. Advances in multi-electrode recording techniques allow study of the dynamics of neuronal populations' activity and its role in information coding. In this report, the hippocampal neurons from rats were cultured on a multi-microelectrode arrays dish and their spontaneous activities were recorded. The plotting of interspike interval versus time was used to investigate the characteristics of temporal coding in spontaneous spike trains. The results show that several unique temporal patterns of spike sequences appear twice with detail repeated to within a millisecond in the same spike train, without any specific experimental perturbation. Groups of such repeating sequences occur together, comprising apparent information units. The study demonstrates that intricate patterns of precisely temporal structures are one of the main forms of temporal coding, and may encode information even during spontaneous activity. This finding may further the understanding of the complex neuronal coding in spontaneous activity in vitro or in vivo.