Memories on the Clock: A Frequent Flyer’s Nightmare

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Science Translational Medicine  26 Nov 2014:
Vol. 6, Issue 264, pp. 264ec202
DOI: 10.1126/scitranslmed.aaa2067

We frequently blame our forgetfulness on lack of sleep. This excuse—which does not elicit much sympathy in the workplace—has gained support from recent studies by Fernandez et al.

Lack of sleep is quite frequently the consequence of changes in our circadian rhythm, a metabolic process governed by a complex cellular network in the brain. Circadian dysfunction is quite common in humans and has been cited as a cause of disorders from anhedonia and depression to compulsive eating and obesity. The precise neuronal circuits that underpin circadian processes are difficult to dissect with conventional tools such as cell type ablation or multicellular gene inactivation. Each of these manipulations has drawbacks that interfere with their usefulness in elucidating circadian circuits.

In an elegant set of experiments, Fernandez et al. now use light pulses to change the activity of the suprachiasmatic nucleus (SCN), the circadian rhythm control center in the brain. These experiments have been done in Siberian hamsters—not because of any association of Siberia with deep freeze and darkness—but because these animals are particularly sensitive to light. Exposure of the SCN to a sequence of light pulses leaves it genetically and structurally intact but completely disrupts the hamster’s circadian rhythm within a few days. Animals with disrupted circadian rhythms showed greatly impaired recognition and spatial memory. Unexpectedly, the authors were able to bring the memory back, but at a high price—ablation of the SCN.

These studies open up the possibility of intervention for cognitive and memory problems during aging or neurological diseases by control of circadian rhythms.

F. Fernandez et al., Dysrhythmia in the suprachiasmatic nucleus inhibits memory processing. Science 346, 854–857 (2014). [Abstract]

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