A Circuit Neuroscience Seminar (CNS)

Nonlinear, multiplication-like operations carried out by individual nerve cells greatly enhance the computational power of a neural system, but our understanding of their biophysical implementation is scant. I pursue this problem in the ON motion vision circuit of Drosophila melanogaster, where neural activity and connectivity are highly stereotyped. I record the membrane potentials of direction-selective T4 neurons and of each of their five columnar input elements in vivo and under identical conditions in response to visual and pharmacological stimuli. My electrophysiological measurements and conductance-based simulations suggest a passive supralinear interaction between two distinct types of synapse on the T4 dendrite. I show that this multiplication-like operation arises from the coincidence of cholinergic excitation and release from glutamatergic inhibition. The latter depends on the expression of the glutamate-gated chloride channel GluClα in T4 neurons, which sharpens the directional tuning of the cells and shapes the optomotor behaviour of the animals. Interacting pairs of shunting inhibitory and excitatory synapses have long been postulated as an analogue approximation of a multiplication, which is integral to theories of motion detection, sound localization, and sensorimotor control. Based on information about approximately 85% of a T4 neuron’s dendritic input signals, my talk will provide both a detailed biophysical account and an intuitive understanding of how a single neuron uses multiplication to compute the direction of visual motion.Y?

Bio: I obtained a medical degree from the Medical University of Graz, Austria, and a DPhil from the University of Oxford, UK, where I studied perceptual decision-making in fruit flies. Currently, I am a postdoc at the Max Planck Institute of Neurobiology in Martinsried, Germany, where I study neural information processing in the visual system. I have discovered molecular mechanisms by which single nerve cells can add up (Groschner et al., Cell 2018) and multiply individual synaptic inputs (Groschner et al., Nature 2022).

Join via Zoom: https://bristol-ac-uk.zoom.us/j/92135942335