Dynamic Computations in the Retina

Retinal Direction Selectivity

Direction-selective retinal ganglion cells (DSGCs) respond preferentially to motion in one direction, a property shaped by asymmetric input from starburst amacrine cells. Surprisingly, we discovered that a brief period of repetitive stimulation can reverse a cell’s preferred direction by 180°. We use this reversal to uncover novel mechanisms of direction selectivity and explore how fixed circuit architecture can support dynamic computation — allowing us to probe the structure-function relationships within retinal circuits.

**Dynamic computing in DSGC.** Directional tuning of a DSGC before and after repetitive stimulation in the form of 40 sec of drifting grating, revealing a reversal of directional preference. Polar plot represents the number of spikes in response to 3 sec of grating drifting in 12 different directions. Red arrow indicates the preferred direction. Traces show examples of 0.5 s spiking activity. Adapted from Ankri et al., 2020.

Visual neurons are known for their antagonistic center-surround receptive field organization, responding to light onset in the center receptive field but to light offset in the surround (or vice versa). This organization is thought to sharpen visual acuity, but the center-surround balance is dynamic, adapting to the light conditions and visual requirements. Our findings reveal that center-surround organization contributes not only to spatial resolution, but also to motion direction encoding. Specifically, we found that changes in the center-surround balance can underlie reversals in direction selectivity, highlighting a novel computational role for this classic circuit motif.