Thalamic Nuclei

Sparse thalamocortical cell population synchronicity during sleep spindle oscillations has been hypothesized to promote the integration of hippocampal memory information into associated neocortical representations 1. We asked the question of whether sparse or rhythmic activity in thalamocortical cells of the reuniens nucleus influence memory consolidation and cognitive flexibility during learning after sleep. For this study, I designed a novel attentional set-shifting task and incorporated optogenetics with closed-loop stimulation in sleeping rats to investigate the effects of sparse (nonrhythmic) or rhythmic spindle-like (~10Hz) activity in thalamic cells of the reuniens nucleus on learning and cognitive flexibility. We show that, as predicted, post-sleep setshifting performance improved after sleep with non-rhythmic optogenetic stimulation in the thalamic nucleus reuniens relative to rhythmic optogenetic stimulation. While both non-rhythmic and rhythmic optogenetic stimulation led to an increase in perseverative errors, only non-rhythmic optogenetic stimulation showed effects of learning from errors, which correlated with sleep, and which ultimately had a net benefit in set-shifting performance compared to rhythmic optogenetic stimulation and the control group.