Inhibitory silencing enhances encoding precision of neuronal ensembles

<p>Neuronal ensembles are structured groups of coactive neurons associated with motor, sensory, and behavioral functions. However, how ensembles encode information remains unclear. To explore this, we investigated the responses of layer 2/3 visual cortical neurons in awake mice using two-photon volumetric calcium imaging during visual stimulation. We detected neuronal ensembles employing an unsupervised model-free algorithm. In response to visual stimuli, ensembles exhibited small trial-to-trial variability and high orientation selectivity. During an ensemble occurrence, besides neurons that were significantly activated by the stimulus, we also found neurons whose activity was significantly decreased in response. To distinguish between these two groups of neurons, we introduced the term "onsemble" for the significantly active neurons and "offsemble" for the silenced ones. Calcium decay kinetics in offsemble neurons significantly decreased during stimulus presentation, indicative of selective inhibition. Ensembles predicted visual stimulus orientation better than averaging the activity of individual onsemble or offsemble neurons. We conclude that the combined activation and inhibition of onsemble and offsemble neurons enhances visual encoding. Therefore, ensembles could be functional units representing information in cortical circuits, combining selectively activated and silenced neurons as an emergent and distributed neural code.</p>