The directional selective retinal circuit: From ion channels to behavior

The primary goal of my laboratory is to define the anatomical and functional properties of parallel neural circuits and relate them to specific computations and behaviours. In particular, we have focussed on a specialized circuit in the retina, which computes the speed and direction of moving images. This directionally selective (DS) circuit produces a biased response in its output element, the DS ganglion cell (DSGC), and allows it to respond to objects moving in a “preferred” direction but not in the opposite or “null” direction1. Information encoded by DSGCs is indirectly relayed to the eye muscles via the accessory optic system, allowing these cells to direct compensatory reflexive eye movements to help stabilize images on the retina. In this proposal, using a multidisciplinary approach including molecular, electrophysiological and two-photon imaging and behavioural assays we ask three fundamental questions relevant to motion coding in the DS circuit (Fig. 1): 1) How do electrical connections between DSGCs help them anticipate moving objects? 2) How do active dendritic properties contribute to the DS processing capabilities of DSGCs? 3) What role do DSGCs play in visually guided reflexive eye movements? Given the multiple levels of novelty encompassed in this proposal, results from these experiments are bound to yield results that are of broad interest to neurobiologists, scientists interested in sensory perception in general and vision in particular, and to any reader with an interest in the computational mechanisms of the brain. In addition, these studies would directly improve our understanding of diseases associated with malfunction of directed eye movements (e.g. Congenital Idiopathic Nystagmus, characterized by involuntary oscillations of the eyes), which are known to map to the DS circuitry in the retina2.