Figure 4.

mPFC single-unit entrainment to hippocampal theta oscillations during start-box occupancy of dual-task sessions. A, Example schematic of mPFC single-unit entrainment to the dorsal hippocampal theta oscillation during start-box occupancy of a good DA epoch. Top, High-amplitude theta oscillations in the hippocampal LFP. Middle, Raw hippocampal LFP in gray, with filtered theta oscillations superimposed in red. Bottom, Spikes emitted by a simultaneously recorded mPFC single unit (one tick mark = one spike). Dashed gray lines demonstrate that spikes from this neuron tended to occur around the peaks of the simultaneously recorded hippocampal theta oscillation. B, Rose plot with hippocampal theta phase (degrees) on the circumference, proportion of spikes emitted in blue histogram bins, and MRL in red from a representative mPFC neuron recorded during start-box occupancy of a DA epoch. Note the nonuniform spike-phase distribution, indicating that spikes tended to occur around the 200° phase of the simultaneously recorded dorsal hippocampal theta oscillation. C, Left, Normalized MRL scores were significantly different between session types and normalized MRL scores during both-good sessions were significantly <0. Right, As in left, but for normalized Rayleigh's z-statistic scores. Error bars indicate means and 95% confidence intervals for 1-sample t tests with 0 null. Bars with asterisks above them indicate a significant main effect of session type for a one-way ANOVA. Asterisks below individual bars indicate a significant deviation from 0 for a 1-sample t test. *p < 0.05, **p < 0.01, ***p < 0.001.