The brain uses several tools to synchronize its circadian rhythm with various environmental effects. Dr. Lawrence P. Morin is examining two of these “tools:” the vestibular system that maintains the body’s balance and the visual system that perceives light and dark. This research will lead to an understanding of the effects of equilibrium-related stimuli on the circadian rhythm system.
Overview
Circadian and Vestibular System Relationships
Principal Investigator:
Lawrence P. Morin, Ph.D.
Organization:
State University of New York - Stony Brook
Technical Summary
This project sought to investigate the relationship between the vestibular system and circadian rhythmicity at a behavioral and anatomical level. The logic for the project was based upon suggestions that the medial vestibular nucleus (MVe) might connect with the intergeniculate leaflet (IGL) of the circadian system. Specific aims were devoted to optokinetic visual manipulations in an attempt to induce illusionary distortions of the vestibular system that might mimic non-photic stimuli known to modify circadian rhythm phase. These studies were unsuccessful. However, the project also addressed anatomical issues related to connectivity between the circadian and vestibular systems.
These studies yielded three large papers and an extremely important result. Namely, they demonstrate the convergence of three brain networks hitherto considered substantially separate. In particular, the IGL has extremely wide-spread interconnections with much of the subcortical brain, which are generally bilateral and reciprocal. Many of the areas with which the IGL is connected also receive vestibular input and/or project to the MVe. Finally, the data demonstrate that many of the regions connected to both the MVe and IGL are also recipients of projections from the hypocretin-containing sleep regulation system. It is likely that, in some fashion, the IGL contributes to the regulation of rapid eye movements during sleep.
Earth Applications
The anatomical results have enormous implications for the study of sleep, vestibular and circadian systems, and how they interact.
This project's funding ended in 2004