Serial dependency in the discharge pattern of dorsal spinocerebellar tract neurons: a computer simulation analysis

We have developed a model in order to analyze the factors eventually responsible for the strong negative serial dependency between successive interspike intervals in the discharge of the Dorsal Spinocerebellar Tract (DSCT) neurons. This dependency is reflected, phenomenologically, by short intervals followed by long ones and, quantitatively, by the first order correlation coefficient (R1-2); which can be lower than -.6 (Jansen, Nicolaysen & Rudjord, 1966; Kröller and Grüsser, 1982). We have found that the lowest values of R1-2 are always related with model parameter values which were very similar to those obtained experimentally. It was observed that EPSP amplitude distribution plays an important role in the discharge patterns of the DSCT neurons. There is one fiber that elicits EPSPs greater than 6 mV, which is responsible for the genesis of the short intervals in the discharge. Long intervals are determined basically by a suprathreshold depolarization and the afterhyperpolarization processes.