Abstract
During low arousal states such as drowsiness and sleep, cortical neurons exhibit rhythmic slow wave activity associated with periods of neuronal silence. Slow waves are locally regulated, and local slow wave dynamics are important for memory, cognition, and behaviour. While several brainstem structures for controlling global sleep states have now been well characterized, a mechanism underlying fast and local modulation of cortical slow waves has not been identified. Here, using optogenetics and whole cortex electrophysiology, we show that local tonic activation of thalamic reticular nucleus (TRN) rapidly induces slow wave activity in a spatially restricted region of cortex. These slow waves resemble those seen in sleep, as cortical units undergo periods of silence phase-locked to the slow wave. Furthermore, animals exhibit behavioural changes consistent with a decrease in arousal state during TRN stimulation. We conclude that TRN can induce rapid modulation of local cortical state.
Highlights
Modulation of arousal is one of the central aspects of behavior, as sleep plays an essential role in cognitive function and survival
We implanted four mice with stereotrodes distributed across cortex and an optical fiber targeting the somatosensory sector of thalamic reticular nucleus (TRN) (Figure 1a)
The amplitude of the negative-going peak was smaller during stimulation, whereas the amplitude of the positive-going peak was larger during stimulation, similar to the asymmetric waveforms typically seen during sleep slow waves (Vyazovskiy et al, 2009)
Summary
Modulation of arousal is one of the central aspects of behavior, as sleep plays an essential role in cognitive function and survival. The slow wave marks rhythmic periods of suppression in cortical neurons (OFF periods) lasting hundreds of milliseconds (Vyazovskiy et al, 2009; Steriade et al, 2001). These brief offline periods are a candidate mechanism for decreased arousal, and slow waves in local cortical regions are associated with behavioral deficits on sub-second timescales (Vyazovskiy et al, 2009). Slow wave activity is locally regulated both during sleep, where it plays a role in sleep-dependent memory
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