Stochastic description of complex and simple spike firing in cerebellar Purkinje cells.
Theoretical Neurobiology, University of Antwerp, Universiteitsplein 1, B2610, Antwerp, Belgium.
Cerebellar Purkinje cells generate two distinct
types of spikes, complex and simple spikes, both of which have
conventionally been considered to be highly irregular, suggestive of
certain types of stochastic processes as underlying mechanisms.
Interestingly, however, the interspike interval structures of complex
spikes have not been carefully studied so far. We showed in a previous
study that simple spike trains are actually composed of regular
patterns and single interspike intervals, a mixture that could not be
explained by a simple rate-modulated Poisson process. In the present
study, we systematically investigated the interspike interval
structures of separated complex and simple spike trains recorded in
anaesthetized rats, and derived an appropriate stochastic model. We
found that: (i) complex spike trains do not exhibit any serial
correlations, so they can effectively be generated by a renewal
process, (ii) the distribution of intervals between complex spikes
exhibits two narrow bands, possibly caused by two oscillatory bands
(0.5-1 and 4-8 Hz) in the input to Purkinje cells and (iii) the
regularity of regular patterns and single interspike intervals in
simple spike trains can be represented by gamma processes of orders,
which themselves are drawn from gamma distributions, suggesting that
multiple sources modulate the regularity of simple spike trains.
PMID: 17328774 [PubMed - as supplied by publisher]