HOUSTON, Aug. 23 (UPI) -- A University of Houston study suggests the circadian clock affects long-term memory formation, in that learning occurs during an animal's active phase.
Research has long indicated circadian rhythms regulate an animal's behavior and physiology. Arnold Eskin, a professor in the school's department of biology and biochemistry, and colleagues hypothesized the circadian clock might also control memory formation.
The scientists studied long-term memory in the California sea slug (Aplysia californica), an animal active during the day. The slugs were given a piece of seaweed wrapped in netting so the food could not be swallowed. Long-term memory formation was measured by how well the animals remembered the food was inedible.
Greater long-term memory occurred when the animals were trained and tested during the day compared with at night. In contrast, a nocturnal slug species (Aplysia fasciata) formed long-term memories when trained and tested during the night, not during the day.
The researchers said their study indicates the circadian clock can modulate associative learning across species and may regulate many types of long-term memory.
The study appears in this week's online early edition of the Proceedings of the National Academy of Sciences.
