On the location-specific positional and extra-positional information in the discharge of rat hippocampal cells

The informational content in the location-specific discharge of rat hippocampal cells is usually quantified by an average for the entire experimental space. In contrast, in the present work the information that can be obtained from spike counts at each position is considered. Along with the local positional information, measures for the total and extra-positional information are introduced. Their properties are studied and illustrated on simulated and experimentally obtained data. It is demonstrated that these information measures provide a new valuable tool for studying the location-specific activity of rat hippocampal cells even on time scales as short as 100 ms. The measures can be used to investigate place cell responses to arbitrary signals in addition to current position.