Using synchronized brain rhythms to bias memory-guided decisions.

Functional interactions between the prefrontal cortex and hippocampus, as revealed by strong oscillatory synchronization in the theta (6-11 Hz) frequency range, correlate with memory-guided decision-making. However, the degree to which this form of long-range synchronization influences memory-guided choice remains unclear. We developed a brain machine interface that initiated task trials based on the magnitude of prefrontal hippocampal theta synchronization, then measured choice outcomes. Trials initiated based on strong prefrontal-hippocampal theta synchrony were more likely to be correct compared to control trials on both working memory-dependent and -independent tasks. Prefrontal-thalamic neural interactions increased with prefrontal-hippocampal synchrony and optogenetic activation of the ventral midline thalamus primarily entrained prefrontal theta rhythms, but dynamically modulated synchrony. Together, our results show that prefrontal-hippocampal theta synchronization leads to a higher probability of a correct choice and strengthens prefrontal-thalamic dialogue. Our findings reveal new insights into the neural circuit dynamics underlying memory-guided choices and highlight a promising technique to potentiate cognitive processes or behavior via brain machine interfacing.

Medial septal microinfusion of scopolamine disrupts hippocampal activity and trace jaw movement conditioning.

This study investigated the effects of microinfusion of scopolamine into the medial septum (MS Scp) on hippocampal neurophysiology and learning of the rabbit's classically conditioned jaw movement response. The percentage of hippocampal theta slow waves (2-8 Hz) decreased after drug infusion in the MS Scp group but did not change in control groups that received infusion of saline into the MS or scopolamine into the cortex. Unit recordings from the MS Scp group showed significantly smaller conditioning-related hippocampal neural responses than seen in controls, and during conditioning, rabbits in the MS Scp group took significantly longer to reach learning criterion than either control group. Thus, the neural and behavioral impairments previously reported for systemic muscarinic blockade were reproduced by microinfusions restricted to the medial septal nucleus.