244 — Gating and control of primary visual cortex by pulvinar

Visual cortex first receives its driving inputs from lateral geniculate nucleus (LGN) in thalamus, but V1 also receives inputs from the thalamic lateral pulvinar nucleus.

The authors monitored responses of primate V1 in the presence of drifting sinusoidal gratings, and then in the presence and absence of the silencing and stimulating injections to thalamus.

When the neurons in this lateral pulvinar nucleus were temporarily muted, V1 stopped responding to visual stimuli. And when these neurons were excited, V1 receptive fields responded dramatically more sensitively to LGN inputs. In combination, this suggests that LGN inputs are “gated” by pulvinar.

It’s not immediately obvious what role this circuit plays in vision, but it’s clear that pulvinar is responsible for some “top-down” manipulation of the visual information that is provided to V1: If the pulvinar doesn’t want information presented to the visual stream, it won’t be presented.

Why does this thalamic area have master-switch privileges? My hypothesis (based upon very limited domain information) is that some other attention circuit — perhaps an indication that the eyes are in a “blinking” position, or an indication that attention is required elsewhere or to another sense — is modulating the visual input pathway to prevent unnecessary or meaningless data from entering the stream.