Functional Circuitry of the Retina

Abstract

The mammalian retina is an important model system for studying neural circuitry: Its role in sensation is clear, its cell types are relatively well defined, and its responses to natural stimuli—light patterns—can be studied in vitro. To solve the retina, we need to understand how the circuits pre-synaptic to its output neurons, ganglion cells, divide the visual scene into parallel representations to be assembled and interpreted by the brain. This requires identifying the component interneurons and understanding how their intrinsic properties and synapses generate circuit behaviors. Because the cellular composition and fundamental properties of the retina are shared across species, basic mechanisms studied in the genetically modifiable mouse retina apply to primate vision. We propose that the apparent complexity of retinal computation derives from a straightforward mechanism—a dynamic balance of synaptic excitation and inhibition regulated by use-dependent synaptic depression—applied differentially to the parallel pathways that feed ganglion cells.

Parallel Computations in Insect and Mammalian Visual Motion Processing

“…This property approximates the well-known Weber–Fechner relation, which posits that sensory systems encode fractional changes in input, rather than absolute changes [18,28]. In mice and other vertebrates, there is a further hand-off between cell types suited to different light conditions: rod photoreceptors that encode dim light and cone photoreceptors that encode brighter light intensities [14,29]. …”

“…The photoreceptor compressive nonlinearities in the two taxa look similar in their efficacy in compression and in their responses to natural time series, in spite of their divergent molecular implementations [30]. In vertebrates, additional adaptation to both the mean and the distribution of contrast occurs in the neurons postsynaptic to photoreceptors [29,31–34]. …”

Divisive suppression explains high-precision firing and contrast adaptation in retinal ganglion cells

“…Neural computations in the retina are generated by complex circuits that drive the responses of ~30 distinct ganglion cell types (Baden et al, 2016; Demb and Singer, 2015; Sanes and Masland, 2015). Despite the complexity of retinal circuitry, many aspects of the responses of ganglion cells to visual stimuli can be predicted with a straightforward Linear-Nonlinear (LN) cascade model (Shapley, 2009).…”

Parallel Processing of Rod and Cone Signals: Retinal Function and Human Perception

“…What about the converse – does cone adaptation affect rod signals? Adaptation of rod- and cone-derived signals, when studied independently, depends on multiple mechanisms (reviewed by (Burns and Baylor, 2001; Dunn and Rieke, 2006; Demb and Singer, 2015)). These mechanisms include adaptation in the photoreceptors themselves and in post-photoreceptor circuits in retina and cortex.…”