Deviant stimuli! How auditory cortex makes sure you don’t miss them

March 2, 2014

I am writing this week from the Cosyne conference in Salt Lake City. I gave a talk this morning about mixed selectivity in parietal cortex and have also heard great talks from a number of other labs.
Our brains are wired to detect auditory stimuli that are important and might be relevant for behavior. A signature of this is an effect called “Stimulus specific adaptation” or, SSA, a phenomenon in which neural responses to unusual or “deviant” stimuli are larger compared to repeating stimuli (think: beep beep book beep). SSA has been established for some time, but the underlying neural circuits that drive it have remained mysterious. Recent work from Ryan Natan in Maria Geffen’s lab at the University of Pennsylvania tackles this issue. Maria and Ryan took advantage of new tools that make it possible to specifically up and photo-9 down regulate inhibitory neurons and look at the effect on firing rates of excitatory cells known to show SSA. They used this approach to evaluate the role of two classes of inhibitory neurons: PV and SOM interneurons.They found that inhibitory either class of neurons interfered with the SSA: following their manipulation, deviant auditory stimuli no longer “popped out” the way they normally do. By carefully comparing the effect of each manipulation on responses to both standard and deviant tones, they revealed that both interneuron classes drive the affect, but in complementary ways.

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