Interneuron subtypes and orientation tuning

arising from B. V. Atallah, W. Bruns, M. Carandini & M. Scanziani Neuron 73, 159–170 (2012)10.1016/j.neuron.2011.12.013 ; N. R. Wilson, C. A. Runyan, F. L. Wang & M. Sur Nature 488, 343–348 (2012) ; S.-H. Lee et al. Nature 488, 379–383 (2012) Parvalbumin-positive (PV+) and somatostatin-positive (SST+) interneurons are two principal subtypes of cortical GABAergic neurons that differ in morphology, physiological properties and postsynaptic targeting1,2,3,4. Although GABAergic inhibition is known to be crucial for shaping orientation tuning in the visual cortex5,6,7, it is unclear whether PV+ and SST+ interneurons have different roles. Recently, Atallah et al.8, Wilson et al.9 and Lee et al.10 addressed this issue by optogenetically manipulating each interneuron subtype, reaching different conclusions: some investigators found that SST+ neuron activation sharpens orientation tuning9, whereas PV+ neuron activation has little effect8,9, but others found that activation of PV+ but not SST+ interneurons sharpens orientation tuning10. To understand the cause for the discrepancy we examined the impact of several experimental differences among the studies—anaesthesia and the level and duration of optogenetic stimulation—and found that the discrepancies can be largely explained by differences in the level and duration of interneuron activation. There are replies to this Brief Communication Arising by Atallah, B. V., Scanziani, M. & Carandini, M. Nature 508, http://dx.doi.org/10.1038/nature13129 (2014) and El-Boustani, S., Wilson, N. R., Runyan, C. A. & Sur, M. Nature 508, http://dx.doi.org/10.1038/nature13130 (2014).