Davide Raccuglia

A human brain in a deep sleep phase displays highly synchronous activity in some neurons while other neurons become silent. The function of this activity pattern is inevitably linked to the physiological function of sleep which is, until today, not well understood.

To extend our understanding of neural activity during sleep we study the brain of Drosophila, a “simple” organism known to exhibit extended periods of rest which satisfy all criteria of sleep. The GAL4/UAS-System enables us to target distinct subsets of neurons in the flies’ mushroom bodies, a neuronal structure known to play a key role in regulating sleep. To measure spontaneous activity in these neurons we use enhanced calcium sensitive fluorescent proteins capable of detecting calcium transients which were so far undetectable. Further we use a voltage dependent fluorescent protein to establish in vivo measurements of electrical activity in neuronal projections which are inaccessible for classic methods of measuring voltage (figure shows spontaneous unilateral increase in membrane potential in the horizontal lobes of the mushroom bodies and corresponding traces).

Correlating spontaneous activities with the behavioral state of the fly will reveal neuronal mechanisms that characterize differences between sleep and wake phases and thus show basic principles of sleep regulation.