Effect of disrupted circadian rhythms on episodic and procedural memory
Disrupted circadian rhythms have been found to affect a number of learning and memory processes. It was hypothesized that disrupted rhythms would impair episodic but not procedural memory, both of which have not yet been fully assessed. Episodic memory relies on the hippocampus, which is known to be affected by rhythms, while procedural is based in the striatum. To disrupt rhythms, 10 rats received a 24-hour light/dark cycle for 29 days while another 10 rats experienced a 22-hour cycle. A newly developed "what, where, and when" task was used to assess episodic memory, while procedural memory was studied using the visible platform Morris water maze. Both episodic memory and procedural memory were mildly impaired by disrupted rhythms, indicating that circadian rhythms, and more specifically the suprachiasmatic nucleus, have a direct effect on both the hippocampus and the striatum.