Abstract:

The detection and processing of novel stimuli is critical for survival; novelty has powerful effects on attention, learning & memory. Recent work has shown that specific classes of inhibitory neurons in the visual cortex, vasoactive-intestinal peptide (VIP) expressing and somatostatin (SST) expressing cells, are differentially modulated by novelty, and may serve to enhance excitatory stimulus responses through disinhibition. Yet these cell populations contain multiple genetically and morphologically distinct types and it is unlikely that they are uniform in their response to novelty. To investigate diversity in novelty coding, we conducted a survey of neural activity in excitatory, VIP inhibitory, and SST inhibitory neurons in the visual cortex of mice performing a change detection task with familiar and novel stimuli. The effects of stimulus novelty were not limited to sensory representations; behavioral, omission, and task related coding were also influenced by novelty, particularly in VIP neurons. By tracking the activity of individual neurons over days, we found striking diversity in single cell coding properties following repeated stimulus exposure. Unsupervised clustering revealed distinct groups of neurons that differed in the direction and dynamics of coding changes, being either transiently enhanced or suppressed by novelty, or showing more stable coding over days. These unique functional subpopulations may contribute to distinct aspects of novelty processing and subsequent familiarization, such as initial detection of novelty, maintaining learned representations, or associating new stimuli with reward and behavioral actions. 

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