Imaging function and development of neuronal circuits of the visual system of the zebrafish

ROMANO, SEBASTIÁN A.

Rio de Janeiro

Simposio; FALAN Young Investigator Symposium: From cell biology to circuits in the visual system; 2017

FALAN

Brain function relies on the interaction of large neuronal populations. Anomalies of these complex neuronal circuits are associated with diverse brain disorders. Therefore, to understand brain function both in health and disease, we must study the processes that rule the establishment and operation of neuronal circuits. Recent advances in optical methods and optogenetics provide unprecedented possibilities for functional imaging of large neuronal populations, and even whole brains, with single-neuron resolution.I will present our recent results on the functional organization and development of the visual system of the larval zebrafish. For this, we applied in vivo two-photon calcium imaging and machine learning computational algorithms to analyze the spontaneous and visually induced activity of hundreds of simultaneously monitored neurons of the optic tectum, the largest visualcenter of the zebrafish brain. We show that the tectal circuitry is organized in distinct assemblies that group functionally similar neurons and are associated to visuo-motor behaviors. Visual experience shapes tectal maturation, since deprivation of retinal inputs throughout development significantly affects the activity dynamics of the tectum. Furthermore, for their integration into mature tectal circuits, neurons born during development first require pre-synaptic visual inputs,which enables a gradual maturation of their functional properties. However, the tectum also seems to rely on hard-wired developmental programs, since functional neuronal tectal assemblies can still form in the absence of visual afferences and, once established, they can be activated independently of retinal drive. This results demonstrate the interplay between experience-dependent and independent processes that shape sensory circuits.