Inhibition is critical for balanced cortical activity and learning. Parvalbumin-expressing cells (PV) are the most common cortical inhibitory interneurons. Strong PV activation inactivates cortical regions. However, how moderate activation of PV interneurons shapes visual perception and behaviour is not well understood.
A new study in PLOS Biology by Dr Lilia Kukovska (BBSRC DTP PhD student at PDN, now postdoc at the University of Toronto), in collaboration with Dr Natsumi Homma in the lab of Dr Jasper Poort, investigated under what conditions activation of PV cells could enhance visual discrimination performance in mice.
The authors used optogenetic activation of PV cells in transgenic mice to test the effect of moderate activation of PV cells on vision, dependence on activation strength, timing, and task difficulty. They found that moderate PV activation in the primary visual cortex (V1) improved easy but not difficult discriminations. It did so only during the initial 120 ms after stimulus onset, corresponding to the initial sweep of information processing the visual cortex. Both easy and difficult discriminations required undisturbed late phase activity beyond 120 ms, highlighting the importance of sustained V1 activity during visual discrimination. The authors then combined optogenetic activation and two-photon imaging to showed that behavioural effects were associated with response selectivity changes in V1 neurons. Dr Katharina Wilmes at the University of Bern and Dr Claudia Clopath at Imperial College London, collaborators on this study, developed a circuit model with nonlinear activation and strong competitive interactions between V1 cells that could capture the experimental data.
The study demonstrates that early and sustained V1 activity is crucial for perceptual discrimination and delineates conditions when PV activation shapes neuronal selectivity to improve behaviour.
Read the article “Context-dependent activation of V1 parvalbumin interneurons enhances visual discrimination” by Lilia Kukovska, Katharina Wilmes, Natsumi Homma, Claudia Clopath and Jasper Poort at https://doi.org/10.1371/journal.pbio.3003518