Arnaldo Carreira-Rosario
Postdoc, Stanford University
All nervous systems must transition from inactive to active during development. While neural activity early in life is crucial for circuit wiring in many contexts, how the brain “turns on”, and how this initial activity influences subsequent circuit formation, remain unclear in any system. To study this evolutionarily conserved phenomenon from the behavioral to the molecular level, we established the Drosophila embryo as a novel system. Using two complementary imaging preparations we provided the first direct observation of spontaneous network activity (SNA) in Drosophila embryos. Strikingly, this work revealed that the spatiotemporal properties of SNA are highly stereotyped across embryos, arguing that SNA is genetically programmed. To study the impact of this stereotypy on behavior development, we first asked what are the neural mechanisms underlying SNA temporal properties. We found that, prior to SNA, mechanosensory neurons that sense muscle twitching are selectively active. Blocking this sensory input results in premature and excessive SNA. Remarkably, transient inhibition of the same mechanosensory inputs also leads to changes in subsequent larval foraging behavior. This indicates that the spatiotemporal properties of SNA in the embryo shape larval behavior, and is one of the first examples to directly link neural activity during circuit assembly to mature behavior. Our work thus lays the foundation for using the Drosophila embryo to study early spontaneous activity in motor circuit formation, reveals that mechanosensory input dampens initial CNS activity, and demonstrates that spontaneous network activity shapes motor behavior. Finally, these studies argue that sensory feedback during the earliest stages of circuit formation sculpts behaviors analogous to motor learning, a process we term innate motor learning.
