In a lab studying the fly
There was a beaker
And a latex glove supply
And a microscope sitting
Next to a guy
And there was a help tab
Open in Matlab
And a fly mushroom body
And a desk that was sloppy
And a genetic screen
And a cabinet of caffeine
And a channel and a cell
And a silica gel
And industrious, brainy lab personnel
Goodnight microscope next to the guy
And the glove supply
And goodnight computer tab
Goodnight desk that is sloppy
And goodnight mushroom body
Goodnight genetic screen
And goodnight forms of caffeine
Goodnight science journal
And goodnight rhythm diurnal
Goodnight activation channel
And goodnight APL cell
Goodnight silica gel
And goodnight to the hardworking lab personnel
Goodnight GABA molecule
Goodnight DPM pair
And goodnight sleeping flies everywhere
– by Margaret Wise Brown (with slight revision by Anja Payne)
Like the ever-wise Margaret Wise Brown, Leslie Griffith and her lab are interested in how sleep is generated. Unlike Margaret Wise Brown, however, the Griffith lab’s interest in sleep goes beyond the parental desire to ease bedtime routines. The Griffith lab is working to answer key questions about sleep such as how the brain changes during sleep and whether these changes are involved in learning and memory.
In order to investigate these questions, the Griffith lab uses Drosophila Melanogaster to probe the role that specific neurons play in sleep and memory consolidation. In their recent paper (Griffith et. al, 2015) they demonstrate that the dorsal paired medial (DPM) neurons are able to promote sleep. Since DPM neurons are also involved in memory consolidation, this paper is one of the first to identify a shared anatomical location for both sleep and memory.
The effect of DPM neuronal activation on sleep occurs via the release of serotonin (5HT) and GABA onto α’/β’ mushroom body (MB) neurons. Activation of DPM neurons during memory consolidation results in inhibition of α’/β’ MB neurons. Since α’/β’ MB neurons are wake-promoting, inhibition of these neurons results in a decrease in sleep. The discovery that DPM neurons inhibit MB neurons is a novel finding and raises many questions regarding the circuit-level function of these neurons.
Several explanations for the utility of DPM inhibition have been proposed. One proposed explanation is that inhibition of α’/β’ MB neurons may impose a directionality on MB feedback which would lead to memory transfer and consolidation. This explanation parallels findings in mammals that show that broadly-projecting inhibitory neurons may coordinate excitatory activity in the hippocampus and neocortex which may control the timing of replay events during sleep.
For further information, and for the benefit of your own edification, come see Dr. Leslie Griffith perform on Tuesday, January 5th, 2016 in the CNCB Marilyn Farquhar Seminar Room and/or refer to the paper below.
Haynes P. R., Christmann B. L., Griffith L. C. (2015). A single pair of neurons links sleep to memory consolidation inDrosophila melanogaster. eLife 4:e03868.
Anja Payne is a first-year Neuroscience graduate student at UCSD. Her neuro-scientific interests include almost everything under the sun with an ever-so-slight focus on learning and memory. Her non-scientific interests include zoos, beaches, puzzles, and her adorable, scruffy, mutt.