Project Details
Projekt
Origin and function of imprecise connectivity in motion-detection circuits
Applicant
Professorin Dr. Marion Silies
Subject Area
Developmental Neurobiology
Molecular Biology and Physiology of Neurons and Glial Cells
Molecular Biology and Physiology of Neurons and Glial Cells
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 453877723
Visual motion detection is a well-studied computation that ensures robust behavioral responses to variable environmental conditions. The circuit motifs involved in the computation of direction-selective responses, a hallmark of motion detection, are known. These motifs are thought to repeat in each column of a retinotopic visual systems, such that the same motion cues are computed in each unit of the eye. However, connectome analysis revealed heterogeneous connectivity of (Tm) medulla neurons across columns. We hypothesize that, during development, different groups of neurons occupy different, non-overlapping spatiotemporal windows of synaptic partner availability leading to precise connectivity between Tm neurons and their major presynaptic inputs. Cell-type specific filopodial dynamics then contribute to imprecise connectivity between Tm neurons and their heterogeneous presynaptic partners. Postsynaptic to the Tm and other (Mi) medulla neurons are the direction-selective T4/T5 cells. Our recent work demonstrated that two T4/T5 subtypes show a unimodal and two T4/T5 subtypes show a bimodal spatial arrangement of presynaptic connectivity. These patterns match functional measurements of direction-selectivity at the population level (Henning et al. 2022). We hypothesize that spatially precise vs. imprecise connectivity between different subtypes of T4/T5 cell types and their presynaptic partners originates from differential spatiotemporal access to presynaptic partners. Overall, our work will address how, at two synaptic layers within motion-detection circuits, the correct interplay of precise and imprecise processes before and during synapse formation leads to patterns of connectivity that are ultimately important for robust function. We will track these processes during development using fixed and live cell imaging and combine this with manipulations that aim to perturb these patterns in a controlled way. We will link development to function by using functional in vivo 2-photon imaging and behavioral analysis under normal and challenging visual conditions, testing if imprecise connectivity leads to functional robustness. This will give us insights into how developmental processes shape the distinct wiring patterns that are important for robust motion computation.
DFG Programme
Research Units
