Pgh. Clarke et al., A CENTRIFUGALLY CONTROLLED CIRCUIT IN THE AVIAN RETINA AND ITS POSSIBLE ROLE IN VISUAL-ATTENTION SWITCHING, Visual neuroscience, 13(6), 1996, pp. 1043-1048
The isthmo-optic nucleus (ION) is the main source of efferents to the
retina in birds. Isthmo-optic neurons project in topographical order o
n amacrine cells in the ventral parts of the retina, and a subclass of
these known as proprioretinal neurons project onto the dorsal retina.
We propose that, through the intermediary of the amacrine target cell
s, activity in the isthmo-optic pathway excites ganglion cells locally
in the ventral retina but inhibits those in dorsal regions. This circ
uit would thereby mediate centrifugally controlled switches in attenti
on between the dorsal retina, involved in feeding, and the more ventra
l parts, involved in scanning for predators. This hypothesis accounts
for a wide range of disparate data from behavior, comparative anatomy,
endocrinology, hodology, and neurophysiology.