Parvalbumin-Expressing Interneruons Linearly Transform Cortical Responses to Visual Stimuli

Atallah, BV. Bruns, W. Carandini, M. Scanziani, M. (2012) Parvalbumin-Expressing Interneurons Linearly Transform Cortical Responses to Visual Stimuli. Neuron 73: 159-170.

Another paper from Massimo's lab. Bass is a good friend. He's in portugal now.


Archeorhodopsin and ChR2 expressed in PVs. Targeted loose-patch ephys. In Layer 2/3. Drifting gratings.

Different response properties of PV and Pyr. PV much more broadly tuned (orientation). Pyramids have a much faster saturation in their contrast response compared to PV.

PV greatly influences Pry spike-rate, but does not change orientation tuning much. There is some slight change that is significant, but this is mainly attributed to the slight increase in Pyr activity. Near the range around threshold can morph the responses slightly in a non-multiplicative fashion. However, this is small.

PV influence on Pyr can be described with a linear-threshold function (since Pyr rate > 0). There is both a scaling factor and a additive factor.

They have a conductance model that explains the tuning properties. This model is basically a rate-coded model. They calculate the equilibrium voltage from conductance measurements (thus conductance changes from PV), and then pass the voltage through a non-linear spiking function. No actual spikes are generated (by passing the Holt-Koch problem). The non-linear function may play an important role as it is exponential - the voltage changes look additive, but the exponential may be making it look multiplicative in the end.

This directly contradicts the Lee, Dan Paper. It does seem possible that strong activation of PV, as opposed to the more moderate activation here, could result in different properties (especially since there is a small additive component).