Christian, J. A. | Search bioRxiv

bioRxiv2026

Sexually dimorphic plasticity of PV inhibition in sensory neocortex during learning

Neocortical parvalbumin-expressing (PV) neurons critically regulate circuit excitation by strong synaptic inputs onto local pyramidal (Pyr) neurons. Plasticity in PV-mediated inhibition during learning could have pronounced effects on gating excitatory synaptic plasticity and circuit excitability, but experimental evidence to support this input- and target-specific plasticity is scant. Here, we combined in vitro electrophysiology with quantitative synapse analysis to determine whether training in a whisker-based sensory-association task could alter PV-mediated inhibition in the primary somatosensory cortex of mice. Using light-evoked activation of channelrhodopsin-expressing PV neurons, we found that evoked PV-IPSCs in Pyr neurons from layer (L) 2/3, but not L5, were rapidly suppressed at the onset of training. This reduction was sex-specific, occurring only in females. The training-related decrease in PV output was accompanied by a reduced number of PV-associated synapses on both the soma and dendrites of L2/3 Pyr neurons, suggesting a postsynaptic structural change. Notably, when whisker stimulation was decoupled from the water reward during pseudotraining, PV-mediated inhibition remained stable. Thus, reduced PV inhibition in superficial layers is an early response to the development of stimulus-reward associations during sensory learning. In addition, these data underscore the importance of including sex as a biological variable in studies of learning-related cortical plasticity.

neuroscience↗

bioRxiv2023

Stimulus-reward contingencies drive long-lasting alterations in neocortical somatostatin inhibition during learning

Learning involves the association of discrete events in the world to infer causality, likely through a cascade of changes at input- and target-specific synapses. Transient or sustained disinhibition may initiate cortical circuit plasticity important for association learning, but the cellular networks involved have not been well-defined. Here we show that sensory association learning drives a durable, target-specific reduction in inhibition from somatostatin (SST)-expressing GABAergic neurons onto pyramidal (Pyr) neurons in superficial but not deep layers of mouse somatosensory cortex. Critically, SST-output was not altered when stimulus and rewards were unpaired, indicating that these neurons are not modified by sensory input alone. Depression of SST output onto Pyr neurons could be phenocopied by chemogenetic suppression of SST activity outside of the training context. Thus, neocortical SST neuron output is persistently modified by convergent sensory and reinforcement signals to selectively disinhibit superficial layers of sensory neocortex during learning.

neuroscience↗