MLI Activity Correlates with Conditioned Eyelid Behavior
Recent findings showed conditioned simple spike suppression in the absence of MLI feedforward inhibition by GABAergic neurotransmission . Yet, the existence of conditioned CS-related complex spike responses reported here raises the possibility of conditioned CS-related MLI activation, either through glutamate spillover or ephaptic inhibition. During our experiments, we recorded a set of 13 interneurons in the molecular layer, all of which showed significant increases in their firing frequency in the ISI. Cell-wise, the mean onset of modulation correlated with the mean CR onset (n = 13, r = 0.582, p = 0.03675). Within the dataset, six MLIs individually showed significant positive trial-by-trial correlations between firing frequency in the ISI and CR amplitude; two cells showed significant negative correlations to CR amplitude (despite an overall increase in firing frequency in the ISI; ). In one case, we were able to record a block of paired trials during the recording of an MLI immediately adjacent to a Purkinje cell from which we also recorded a block of paired trials. The latencies of the modulation of these cells were complementary , as were their correlations to behavior. Using the same correlation matrix approach explained above, the six positively correlating MLIs showed focal areas that complement those found in the Purkinje cell simple spike correlation matrix , with a diagonal area focused near the end of the ISI and centered at an offset of approximately 50 ms between spikes and subsequent eyelid position, and again an early vertically oriented focal area. Here too, mean spike and eyelid traces for cells split on whether they showed this early focal area or not were in line with this distinction . The two negatively correlating MLIs showed only a focal area near the end of the ISI