Parametric Functional Maps of Visual Inputs to the Tectum

How features of the visual scene are encoded in the population activity of retinal ganglion cells (RGCs) targeting specific regions of the brain is not well understood. To address this, we have used a genetically encoded reporter of presynaptic function (SyGCaMP3) to record visually evoked activity in the population of RGC axons innervating the zebrafish tectum. Using unbiased voxel-wise analysis of SyGCaMP3 signals, we identify three subtypes of direction-selective and two subtypes of orientation-selective retinal input. Composite parametric functional maps generated across many larvae show laminar segregation of direction- and orientation-selective responses and unexpected retinotopic biases in the distribution of functional subtypes. These findings provide a systematic description of the form, organization, and dimensionality of visual inputs to the brain and will serve as a platform for understanding emergent properties in tectal circuits associated with visually driven behavior. ► Fine-scale functional imaging of retinotectal inputs at the population level ► Voxel-wise analysis reveals direction- and orientation-selective retinotectal inputs ► Direction- and orientation-selective inputs segregate into distinct laminae ► Composite maps show retinotopic biases in directional and orientational inputs The functional organization of sensory terminals within the brain is insufficiently characterized. Nikolaou et al. provide maps of retinal inputs to the zebrafish tectum that reveal segregation according to functional class. Their approach illustrates the strength of examining inputs en masse.