Recording the entire visual representation along the vertical pathway in the retina

Abstract

 

Purpose

 

In the retina, the stream of incoming visual information is split into multiple parallel information channels, represented by different kinds of photoreceptors (PRs), bipolar (BCs) and retinal ganglion cells (RGCs). Here, we record from the majority of these cells in the vertical cone pathway using two-photon (2P) Ca2+ imaging in the mouse retina. This dataset allows us to study the computations performed along the retina’s vertical pathway and to obtain a complete sample of the information the mouse eye sends to the mouse brain.

 

Methods

 

We recorded light-evoked Ca2+ activity from BC synaptic terminals and RGCs loaded with synthetic Ca2+ indicator dyes in intact whole-mounted mouse retina using 2P microscopy. Light evoked activity of cone PRs was recorded in slices using transgenic animals expressing a genetically encoded Ca2+ indicator (Wei et al., 2012). Simple full-field light stimuli were used. Single cell activity patterns could be clustered into at least 8 functional BC types and at least 15 functionally distinct RGC types (Baden et al., in press). In addition, we presented spatially modulated to identify different previously described functional types such as direction selective GCs

 

Results

 

We found 8 functional BC types, which match anatomical types and project to the inner retina in an organized manner according to their response kinetics. The fastest BC types generate clear all-or-nothing spikes. In addition, we found >15 functional RGC types, including classic ON- and OFF as well as transient and sustained types. We verified the functional clustering using anatomical data.

 

Conclusions

 

Our data suggest that neurons of the retina’s vertical pathway can be clustered into functionally defined classes based on their Ca2+-responses to simple light stimuli.This local retinal “information fingerprint” should be very informative for our understanding of neuronal computations in the healthy retina and as a research tool for evaluating specific functional deficiencies in diseased or degenerating retinae.

 

 

A. Ganglion cell layer labeled with Ca2+ indicator dye. B. Color-coded activity, indicating cells responsive to light-onset (green), -offset (red) and/or frequency modulation (blue). C. Functional clustering of RGCs into 16 types based on response features to the full-field stimulus shown above. Response clusters include ON- and OFF as well as transient and sustained types.

 

Keywords: 691 retina: proximal (bipolar, amacrine, and ganglion cells) • 689 retina: distal (photoreceptors, horizontal cells, bipolar cells) • 549 image processing