All-optical interrogation of a direction selective retinal circuit by holographic wave front shaping

Abstract

Direction selective (DS) ganglion cells (GC) in the retina maintain their tuning across a broad range of light levels. Yet very different circuits can shape their responses from bright to dim light, and their respective contributions are difficult to tease apart. In particular, the contribution of the rod bipolar cell (RBC) primary pathway, a key player in dim light, is unclear. To understand its contribution to DSGC response, we designed an all-optical approach allowing precise manipulation of single retinal neurons. Our system activates single cells in the bipolar cell (BC) layer by two-photon (2P) temporally focused holographic illumination, while recording the activity in the ganglion cell layer by 2P Ca 2 imaging. By doing so, we demonstrate that RBCs provide an asymmetric input to DSGCs, suggesting they contribute to their direction selectivity. Our results suggest that every circuit providing an input to direction selective cells can generate direction selectivity by itself. This hints at a general principle to achieve robust selectivity in sensory areas.A major goal in neuroscience is to understand the circuits that embody the computations performed by sensory neurons. In particular, a striking feature of sensory processing is the ability of neurons to perform the same computation in different contexts. For example, neurons in the piriform cortex represent odor identity while remaining invariant to its exact concentration (Bolding and Franks, 2018). Similarly, neurons in the visual cortex can keep the same orientation tuning curve over different contrasts (Sclar and Freeman, 1982).In the retina, direction selective (DS) ganglion cells (GC) respond selectively to a motion direction in different contexts such as different backgrounds (Chen et al., 2016), different natural scenes (Im and Fried, 2016), and over a broad range of luminosities (Pearson and Kerschensteiner, 2015; Vaney et al., 2001;Yao et al., 2018). Switching the average luminance from dim to bright light will change the dominant circuits that convey visual information inside the retina, leading to major changes in the responses of ganglion cells (Pearson and Kerschensteiner, 2015;Wässle, 2004). For example, cells will change their ON-OFF polarity (Tikidji-Hamburyan et al., 2015). It is therefore particularly striking that direction selectivity remains constant across the ten billion fold change of luminance separating day from night (Yao et al., 2018), despite the involvement of distinct circuits. A major challenge is to understand how this feature is achieved.During daylight conditions, where rods are saturated and cones transmit light input, the major component responsible for direction selectivity is a functional asymmetry. This results either from an asymmetric inhibition or an asymmetric morphology. For example, in the ON-OFF

Scanless two-photon excitation with temporal focusing

“…Since multiplane TF is a relatively new technology, few biological applications have been reported so far: 3D-SHOT was used to mimic a sensory stimulus 96 . MTF-CGH was used to investigate the contribution of rod bipolar cells to the response of direction selective ganglion cells in the retina 99 . These biological experiments were all performed in superficial cortical layers or using in vitro preparations.…”

New Optical Tools to Study Neural Circuit Assembly in the Retina

“…Given the graded, non-spiking membrane properties of most interneurons, the application of this method to retinal circuitry is likely to be successful. Indeed, a preprint describing this approach in retina indicates that one can stimulate hundreds of rod BCs while measuring responses in a field of RGCs expressing genetically encoded calcium indicators (Spampinato et al, 2019 ).…”

Predicting synchronous firing of large neural populations from sequential recordings

“…Several studies have shown that it is possible to cluster cells in different homogeneous types [ 5 ]. This can be done using either the responses of each cell to several standard stimuli [ 6 – 8 ], or using genetic tools [ 9 , 10 ]. These methods have proven successful in isolating most cell types in the retina [ 7 , 11 , 12 ] and there are several ongoing studies trying to apply these approaches in the cortex [ 13 ].…”