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The generation of cortical novelty responses through inhibitory plasticity

New paper out! In this eLife publication, we show how inhibitory plasticity can affect the neuronal responses to familiar versus novel stimuli.

Schulz A.*, Miehl C.*, Berry II M.J., Gjorgjieva J. (2020). "The generation of cortical novelty responses through inhibitory plasticity." eLife, 10:e65309. * equal contribution

Brief summary:

Animals need to react to changes in their environment very rapidly in order to secure their survival. Therefore, the reliable extraction of behaviorally useful information from sensory stimuli is an important task the brain needs to solve. Specifically, animals need to be able to distinguish unexpected stimuli, i.e. “novel” stimuli, from repeated or predictable stimuli, i.e. “familiar” stimuli, which do not provide new meaningful information. This phenomenon has previously been studied experimentally in the mouse primary visual cortex in the lab of our experimental collaborator, Michael Berry II (Princeton University), who is also a co-author of our study. Among others, these experiments have found that the presentation of a novel visual stimulus leads to a high response of neural firing rates, while the presentation of a familiar visual stimulus leads to lower responses in the visual cortex (Homann et al., 2017). This high cortical response of novel stimuli suggests that such unexpected sensory signals are fast and reliably transmitted from primary sensory cortices to higher-order brain areas. However, it remains unclear which circuit and synaptic mechanisms underlie the different responses of novel versus familiar stimuli. To uncover these mechanisms, we simulate a neuronal network model of excitatory and inhibitory spiking neurons with synapses undergoing long-term plasticity. We demonstrate that our model can generate high cortical responses when a novel stimulus is presented, while repeated or familiar stimuli have decreased responses. Our framework identifies spike-timing-dependent plasticity of inhibitory-to-excitatory synapses (i.e. inhibitory plasticity) as the underlying mechanism of the differential responses of familiar versus novel stimuli. This suggests that inhibitory plasticity plays a key role in the differentiation of sensory stimuli in sensory cortices. Our modeling framework allows us to formulate multiple experimentally-testable predictions. For example, our results suggest that neurons in primary sensory cortices may not signal the violation of periodicity of a sequence but rather adapt to the distribution of presented stimuli. Furthermore, we suggest disinhibition as a potential regulatory mechanism, which can control familiar and novelty responses. In summary, our modeling study suggests that inhibitory plasticity plays an important role in the differential representation of novel versus familiar stimuli in primary sensory cortices.


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