Does the brain’s vestibular system contribute to synchronisation of circadian rhythms?

The primary circadian clock in the brain, the suprachiasmatic nucleus (SCN), drives ∼24-hour circadian rhythms that help regulate physiology and behaviour. To conform to the environment, circadian rhythms are entrained to zeitgebers "time givers", external cues that assist in resetting of the circadian clock and shift the timing of its rhythms. The primary zeitgeber is light, which is considered a photic input. Additional zeitgebers that can modify circadian rhythms independent of light are known as non-photic stimuli, and are innervated by arousal regions of the brain. The mechanisms by which non-photic stimuli contribute to resetting of the circadian clock are currently not clear; however, evidence indicates that activation of arousal regions is necessary. A concept not yet investigated is the involvement of the sensory vestibular system in non-photic clock resetting. Therefore, this review synthesizes current literature and proposes a novel role for the vestibular system in resetting the circadian clock in a non-photic manner. By providing insight into the potential role of vestibular regulation in circadian rhythmicity, we provide valuable evidence that can be used in the future to develop strategies to mitigate circadian misalignment and subsequent dysfunction.