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Kosiachkin, Y.

Publications and source records attributed to Kosiachkin, Y..

3 recordsLinked to original sources

Distinct Disinhibitory Circuits Link Short-Term Adaptation to Familiarity and Reward Learning in Visual Cortex

Sensory cortices filter repeated inputs through rapid adaptation over seconds and experience-driven learning over days. Although these forms of plasticity occur simultaneously, it is not known how they interact within cortical circuits. We combined two-photon calcium imaging, data-driven circuit modelling and optogenetics to investigate how short-term adaptation in layer 2/3 of mouse V1 is shaped by stimulus familiarity and reward association. Habituation reduced the fraction of pyramidal cells responsive to a visual stimulus, whereas reward association maintained overall responsivity. In contrast, both forms of learning shifted pyramidal cell adaptation from depression toward sensitization, but through distinct circuit mechanisms. Habituation reduced disinhibition through the VIP[->]SST[->]PC pathway by weakening feedback activation of VIPs and VIP[->]SST connections. Reward association counteracted this effect by increasing disinhibition through the SST[->]PV[->]PC pathway, strengthening SST[->]PV connections while reducing SST[->]PC inputs. Despite engaging distinct disinhibitory circuits and producing divergent effects on pyramidal cell responsivity, both forms of learning converged on a reduced PV:SST input ratio to pyramidal cells, thereby biasing V1 toward sensitizing adaptation. These results identify changes in cortical circuits that link the plasticity of fast adaptation to simple forms of learning.

neuroscience↗

Locomotion Selectively Amplifies Sensitizing Neurons in Primary Visual Cortex

Sensory processing in the cortex reflects both adaptation to external stimuli and changes in internal state. To investigate how these processes interact in layer 2/3 of mouse V1 we combined calcium imaging, optogenetics and circuit modelling. We find that locomotion preferentially increases the responses of pyramidal cells (PCs) that sensitize during visual stimulation compared to those that depress. A model explains this differential modulation through: (i) variations in the strength of PV and SST connectivity to individual PCs, (ii) broad locomotion-dependent weakening of PC and PV synapses, and (iii) reduced SST inhibition targeting sensitizing PCs. Differences in PV:SST input ratios across sensitizing and depressing PCs can be reproduced by a random-connectivity model based on measured interneuron densities, connection probabilities and synaptic strengths. Thus, stochastic variation in local inhibitory connectivity can explain much of the functional heterogeneity across PCs, while state-dependent modulation of inhibitory synapses reorganizes this balance during locomotion to bias cortical population activity towards sensitizing dynamics. The apparently paradoxical combination of increased PC response but decreased synaptic strength is consistent with a state-dependent gating mechanism that boosts signals leaving V1 while simultaneously preventing disruption of the local excitatory-inhibitory balance required for stable computation.

neuroscience↗

Random connectivity generates inhibitory microcircuits that decorrelate adaptation in visual cortex

Inhibitory neurons are fundamental to sensory processing in the cortex but the rules governing their connections with excitatory neurons are unclear. Are pyramidal cells with different functions generated through specific or random connections? We used two-photon imaging, optogenetics and modelling to investigate opposing forms of adaptation in layer 2/3 of mouse visual cortex. We find that a slow modulatory drive acts differentially depending on the relative strength of inputs that individual pyramidal cells receive from parvalbumin-positive and somatostatin-positive interneurons. The number of depressing and sensitizing pyramidal cells could be explained quantitatively by the simplest connectivity rule - all inhbitory synapses made randomly. The functional heterogeneity of the pyramidal cell population therefore begins with general statistics of the connectome - interneurons are much sparser and connect with probabilities far less than one. The resulting "patchwork" of inhibitory microcircuits causes modulatory inputs to strongly decorrelate pyramidal cells on the behavioural time-scale of seconds.

neuroscience↗