I’ve just finished correcting the last papers and exams my students did the past few weeks and it means this advice comes a bit late, luckily we’ve known this for quite a while already: sleep, memory and learning are deeply connected. But new research now explains how come by looking in a very peculiar place: the Drosophila. If you don’t know what the drosophila is or what ik looks like (I didn’t):
You might wonder what this little fly can tell us about memory and sleep? Well, it can answer an important question: is memory consolidated during sleep because the brain is quiet, allowing memory neurons to go to work, or are memory neurons actually putting us to sleep?
From the press release:
In a recent paper in the journal eLife, graduate students Paula Haynes and Bethany Christmann in the Griffith Lab make a case for the latter.
Haynes and Christmann focused their research on dorsal paired medial (DPM) neurons, well-known memory consolidators in Drosophila. They observed, for the first time, that when DPM neurons are activated, the flies slept more; when deactivated, the flies kept buzzing.
These memory consolidators inhibit wakefulness as they start converting short-term to long-term memory. All this takes place in a section of the Drosophila brain called the mushroom body, similar to the hippocampus, where our memories are stored. As it turns out, the parts of the mushroom body responsible for memory and learning also help keep the Drosophila awake.
“It’s almost as if that section of the mushroom body were saying ‘hey, stay awake and learn this,'” says Christmann. “Then, after a while, the DPM neurons start signaling to suppress that section, as if to say ‘you’re going to need sleep if you want to remember this later.'”
Understanding how sleep and memory are connected in a simple system, like Drosophila, can help scientists unravel the secrets of the human brain.
“Knowing that sleep and memory overlap in the fly brain can allow researchers to narrow their search in humans,” Christmann says. “Eventually, it could help us figure out how sleep or memory is affected when things go wrong, as in the case of insomnia or memory disorders.”
Abstract of the study:
Sleep promotes memory consolidation in humans and many other species, but the physiological and anatomical relationships between sleep and memory remain unclear. Here, we show the dorsal paired medial (DPM) neurons, which are required for memory consolidation in Drosophila, are sleep-promoting inhibitory neurons. DPMs increase sleep via release of GABA onto wake-promoting mushroom body (MB) α’/β’ neurons. Functional imaging demonstrates that DPM activation evokes robust increases in chloride in MB neurons, but is unable to cause detectable increases in calcium or cAMP. Downregulation of α’/β’ GABAA and GABABR3 receptors results in sleep loss, suggesting these receptors are the sleep-relevant targets of DPM-mediated inhibition. Regulation of sleep by neurons necessary for consolidation suggests that these brain processes may be functionally interrelated via their shared anatomy. These findings have important implications for the mechanistic relationship between sleep and memory consolidation, arguing for a significant role of inhibitory neurotransmission in regulating these processes. – See more at: http://elifesciences.org/content/4/e03868#sthash.ZISJiA5a.dpuf