Pretrial hippocampal θ-state differentiates single-unit response profiles during rabbit trace eyeblink conditioning

Eyeblink conditioning given in the explicit presence of hippocampal θ results in accelerated learning and enhanced multiple-unit responses, with slower learning and suppression of unit activity under non-θ conditions. Recordings from putative pyramidal cells during θ-contingent training show that pretrial θ-state is linked to the probability of firing increases versus decreases rather than to the magnitude of such responses. These findings suggest that the learning facilitation during θ may be due to the recruitment of additional neurons that increase their firing rate during trials.