Constant light desynchronises olfactory versus object and visuospatial recognition memory performance

Journal article

Circadian rhythms optimise physiology and behaviour to the varying demands of the 24-hour day. The master circadian clock is located in the suprachiasmatic nuclei (SCN) of the hypothalamus and it regulates circadian oscillators in tissues throughout the body to prevent internal desynchrony. Here we demonstrate for the first time that, under standard 12-h:12-h light–dark cycles (LD), object, visuospatial, and olfactory recognition performance in C57BL/6J mice is consistently better at midday relative to midnight. However, under repeated exposure to constant light (rLL), recognition performance becomes desynchronised, with object and visuospatial performance better at subjective midday and olfactory performance better at subjective midnight. This desynchrony in behavioural performance is mirrored by changes in expression of the canonical clock genes Period1 and Period2 (Per1 and Per2) as well as the immediate-early gene Fos in the SCN, dorsal hippocampus, and olfactory bulb. Under rLL, rhythmic Per1 and Fos expression is attenuated in the SCN. By contrast, hippocampal gene expression remains rhythmic, mirroring object and visuospatial performance. Strikingly, Per1 and Fos expression in the olfactory bulb is reversed, mirroring the inverted olfactory performance. Temporal desynchrony among these regions does not result in arrhythmicity, as core body temperature and exploratory activity rhythms persist under rLL. Our data provide the first demonstration that abnormal lighting conditions can give rise to temporal desynchrony between autonomous circadian oscillators in different regions, with different consequences for performance across different sensory domains. Such a dispersed network of dissociable circadian oscillators may provide greater flexibility when faced with conflicting environmental signals.

Authors: Tam, S; Hasan, S; Choi, H; Brown, L; Jagannath, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Society for Neuroscience
• Journal: Journal of Neuroscience
• Volume: 37
• Issue: 13
• Pages: 3555-3567
• Publication date: 2017-03-29
• Acceptance date: 2017-02-04
• DOI: 10.1523/JNEUROSCI.3213-16.2017
• EISSN: 1529-2401
• ISSN: 0270-6467
• Keywords: Clock genes; Olfactory bulb; Circadian; Suprachiasmatic nuclei; Hippocampus; Internal desynchrony