EFFECTS OF SPIKE DISCHARGE HISTORY ON DISCHARGE PROBABILITY AND LATENCY IN FROG BASILAR PAPILLA UNITS

Gaumond et al. [(1982) J. Neurophysiol. 48, 856-873] showed in the cat that a multiplicative-intensity model can generally account quite wel l for reduction of the probability of an auditory-nerve spike by anoth er spike preceding it by 4 to 25 ms, and that for smaller separations there is also an increased latency of the following spike. Bosch [(199 0) D. Sc. Dissertation, Washington University, St. Louis, MO] made imp ortant improvements in experimental design and estimation techniques f or studying these effects, and confirmed their presence in the gerbil. However, direct application of these methods to the frog does not yie ld reliable estimates. A clearer separation of discharge probability a nd latency effects in frog basilar papilla units is provided by the pa ired-click paradigm used in this study, which is applicable to low-spo ntaneous-rate units that generally respond to click stimuli with zero or one spike within a short interval following the click. The results confirm the existence in the frog of both spike-probability and spike- latency effects that are qualitatively similar to those found in mamma ls, although the absolute refractory time is much longer in frog, and the relative refractory time usually shorter. The paired-click paradig m also reveals a stimulus-history effect at stimulus levels which are near threshold: when there is no response to the first click, response s to the second click occur with increased probability and reduced lat ency.