22 September 2006

Having friends might make you sleepy

By
Cosmos Online
Having a social life can be exhausting according to a new U.S. study that examined the links between social interactions, sleep and memory in fruit files.
Having friends might make you sleepy

Sociable fruit flies need more sleep than socially isolated flies. Credit: André Karwath

SYDNEY: Having a social life can be exhausting according to a new U.S. study that examined the links between social interactions, sleep and memory in fruit files.

The study, published today in the U.S. journal Science, uses the behavioural and physiological similarities between fruit fly and mammalian sleep, coupled with genetic analysis, to discover genes responsible for the connection between social experience, sleep and memory.

“Flies sleep and they can be trained to form testable memories. This study shows that they also socialise, leading to profound effects on their sleep-need,” said Indrani Ganguly-Fitzgerald from the Neurosciences Institute in San Diego, California, co-author of the study.

Ganguly-Fitzgerald and his colleagues trained fruit flies in complex tasks such as social and courtship interactions, and found that socially enriched flies that formed long term memories needed significantly more sleep than socially impoverished flies. Even being presented with a virgin female did not alter the need for sleep in socially active flies.

The authors also found that disrupting sleep resulted in poor memory of a task, suggesting that sleep plays a vital role in learning and memory, as well as in social interactions.

“This provides us with a simple easy model to try to understand two very hard questions – the function of sleep and experience,” said Ganguly-Fitzgerald.

The authors also established molecular links between sleep and brain re-wiring: 19 memory genes and a neuromodulator – dopamine. When these were switched off in the brain, sleep requirements were no longer affected by socialisation.

“We are attempting to understand why. We show that dopamine and memory genes play a role in this process, but the ‘why’ constitutes future research,” said Ganguly-Fitzgerald.

While the authors established a strong link between sleep and neural activity, they believe there are still many unidentified genes that can provide the link to human genes that affect sleep and memory.

“We hope that this paradigm allows others and ourselves to identify still more genes. I suspect there are many more, and look forward to identifying them,” said Ganguly-Fitzgerald. “From here, we will eventually try to make links with human genes and genetic disorders that impact sleep and memory.”

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