Effects of delta-9-tetrahydrocannabinol on sensory evoked hippocampal activity in the rat: principal components analysis and sequential dependency.

The effects of delta-9-tetrahydrocannabinol (delta-9-THC) were assessed on identified hippocampal sensory evoked potentials obtained from rats during performance of a two-tone discrimination task. Techniques which analyzed the trial-to-trial sequential and serial dependence underlying the variance in evoked potential amplitude were utilized. Waveforms of averaged tone-evoked potentials (AEPs) recorded from the outer molecular layer of the dentate gyrus (OM) were subjected to principal components analysis which revealed eight principal components accounting for 90.3% of the total variance in the set of OM AEP waveforms. Five of the eight components were altered significantly in comparison to vehicle injection sessions after administration of either a 1.0- or 2.0-mg/kg dose of delta-9-THC. These alterations accounted for the amplitude and latency changes in the OM AEP described in a previous report. In addition, delta-9-THC also disrupted the trial-to-trial sequential dependency of the OM AEPs. An important result showed that delta-9-THC selectively influenced the serial dependence of the OM AEP. These results implicate delta-9-THC as a potent disruptor of temporally specific information as it is processed by the hippocampus and suggest that such disruption may be the basis of delta-9-THC effects on memory processes in humans.