Possible mechanism of direction selectivity in the archer fish retina

Direction selectivity is a basic neuronal computation mechanism found in various brain areas. The retina sets a good
example of this mechanism: the computation is done in the
retina circuitry, and the retinal ganglion cells' output to the
brain has direction selective features. The accepted model for
this mechanism in mammalian retina is based on the asymmetry of the inhibitory input from starburst amacrine cells to
the retinal ganglion cells. Recently, direction selectivity was
found also in the archer fish retina that could participate in the
neural mechanism enabling fast reaction of the fish to moving
objects. In order to study the directionally selective mechanism in the archer fish retina, we conducted a pharmacological
study of the retinal ganglion cells. We found that blocking of
GABAA receptors eliminates the archer fish retina sensitivity
to motion all together. This is in contrast to the mailman retina
where blocking of GABAA receptors interferes with direction
selectivity alone. These results might indicate a cellular mechanism that differs from the mechanism found in mammals.