Division and subtraction by distinct cortical inibitory networks in vivo.

Wilson, NR. Runyan, CA. Wang, FL. Sur, M. (2012) Division and subtraction by distinct cortical inhibitory networks in vivo. Nature

Optogenetic stimulation with in-vivo two-photon imaging. Custum scan-paths. ChR2 in Cre/loxP mice targeting PV or SOM. OGB calcium dye. Drifting gratings.

Using calcium responses can get tuning curves. Activation of PV shows a multiplicative effect, SOM shows additive effects (scale, vs shifting tuning curves). They did same experiments with cell-attached recordings of pyramidal cells, got essentially the same results.

They can reduce ChR2-stimulating beam to target a single PV neuron, while concurrently sampling population responses with Ca imaging. They detect different populations that are effected by inidividual neurons. About 43% in view were suppressed by PV, 16% by SOM.

No clear distance relationship with PV or SOM targeted networks - best fit by random connection model. There is a functional relationship, PV cells preferentially targeted pyramids that had similar orientation preference. SOM cells had no connection preference to similar oriented or orthogonal cells. (Does this imply a inh->exc learning rule?)