Enhancement of Hippocampal-Thalamocortical Temporal Coordination during Slow-Frequency Long-Duration Anterior Thalamic Spindles

Temporal nesting of cortical slow oscillations, thalamic spindles, and hippocampal ripples indicates multiregional neuronal interactions required for memory consolidation. However, how the thalamic activity during spindles organizes hippocampal dynamics remains largely undetermined. We analyzed simultaneous recordings of anterodorsal thalamus and CA1 in male mice to determine the contribution of thalamic spindles in cross-regional synchronization. Our results indicated that tempo-ral hippocampo-thalamocortical coupling was more enhanced during slower and longer thalamic spindles. Additionally, spin-dles occurring closer to slow oscillation trough were more strongly coupled to ripples. We found that the temporal association between CA1 spiking/ripples and thalamic spindles was stronger following spatial exploration compared with baseline sleep. We further developed a hippocampal-thalamocortical model to explain the mechanism underlying the duration and frequency-dependent coupling of thalamic spindles to hippocampal activity. Our findings shed light on our understand-ing of the functional role of thalamic activity during spindles on multiregional information transfer.

Automated summary

This study analyzed the impact of thalamic spindles on hippocampal dynamics and found that the coupling between the hippocampus and thalamocortical networks was enhanced during slower and longer spindles. Additionally, spindles occurring closer to slow oscillation troughs were more strongly coupled to hippocampal ripples. The study also revealed that the temporal association between CA1 spiking/ripples and thalamic spindles was stronger after spatial exploration.