Spike Train Statistics from Empirical Facts to Theory: The Case of the Retina - Modeling in Computational Biology and Biomedicine - page 256

a b

Periphery Center

global

B B B B B B

local

time

global
motion

A

G

local motion

Fig. 8.4 Detection of differential motion. ( a ) An object-motion-sensitive G cell remains silent
under global motion of the entire image but fires when the image patch in its RF moves differently
from the background. ( b ) Scheme summarizing the circuitry behind this computation. Rectification
(see [ 13 ] for a description of rectification mechanism.) of B cell signals in the RF center creates
sensitivity to motion. Polyaxonal A cells in the periphery are excited by the same motion-sensitive
circuit and send inhibitory inputs to the center. If motion in the periphery is synchronous with
that in the center, the excitatory transients will coincide with the inhibitory ones, and firing is
suppressed (Figure from [ 24 ]. The legend is adapted from this reference)

It has been long believed that retina was mainly acting as an image transducer,
absorbing photons and producing electrical signals or acting as a temporal and
spatial linear filter. It was also believed that the retina doesn't perform any pre-
processing of the image before sending spike trains to the brain. More recently,
researchers pointed out that retina, in some species, is “smarter” than previously
believed and is able to detect salient features or properties in a image such
as approaching motion, motion detection and discrimination, texture and object
motion, creating predictive or anticipatory coding thanks to “specialized” G cells
(see, e.g., [ 24 ] for a review). The specificity of these population of cells for the
detection of differential motion results largely from the circuit they belong to. An
example is shown in Fig. 8.4 (detection of differential motion) where A cells play a
prominent role.

8.2.2 Multi-electrodes Array Acquisition

The pioneering work of Hubel and Wiesel based on anatomy and single cell
recording on brain visual areas was very useful. However at that time, little was
known about the properties of the retinal neural network. Similarly, today, the
anatomical description of different types of G cells is a well known piece of
literature, in contrast to their collective neural response that is partly missing. To
overcome limitations of single-electrodes recording and to access to the coding
response of a population of neurons, multi-electrodes (MEA) devices are used in
physiology (for references on MEA see [ 69 ]). MEA devices are formed by an array
of isolated electrodes (64-256, separated from 30 to 200

μ m each, see Fig. 8.5 ).