Tirin Moore

Just went to a talk by Tirin Moore from stanford. He studies visual attention and was doing physiology work in FEF and V4. He had a lot of interesting data, but it was kind of all over the place.

His model had neurons with D1 receptors in 2/3 of FEF, and these were the ones that fedback to V4. He showed through antidromic AP annihilation that it was mainly the persistent firing cells that fedback to V4. He showed that modulation of D1 and D2 receptors in FEF have the same effect of behavior -- biasing the saccades to the RFs in FEF (although it was D1 antagonist and D2 agonist, which he said didnt matter because they have "U" shape properties). D1 changes had effects, however, on the properties of V4 neurons -- typically looking like enhanced attention. D2 had no real effect on V4, but had the behavioral result. D2's seemed to be more involved in the motor part of the saccade, and D1 in the attentional part.

It seemed like a clear case of Modulatory type of feedback projections. The neuron's were enhanced by FEF feedback, but required FF stimulation. The fact that the feedback was from the persistent firing neurons made sense to me -- keeping the modulation up in preparation for the stimulus to appear. Although, he said that the selectivity was narrowed, which goes against the kind of gain control modulation that I think of. However, this may just be because you're altering FEF in a non-sensical fashion, and that causes selectivity changes. And he was measuring V4 selectivity with oriented bars.