Excitatory / inhibitory balance in adaptation-induced plasticity and its disruption by anisomycin in mouse visual cortex.

Abstract

Neuroplasticity, the ability of neurons to change their properties in the adult cortex, relies on balanced excitatory and inhibitory (E/I) circuits. Orientation adaptation (prolonged / repeated exposure of an optimal / nonoptimal orientation) can shift neuronal tuning curves, yet the role of E/I balance remains unclear, especially in the mouse cortex. Here, we performed single-unit recordings in the mouse primary visual cortex (V1), before and after 12 min of adaptation, with and without local anisomycin application. We then examined adaptation-induced tuning shifts in regular-spiking (RS; putatively excitatory) and fast-spiking (FS; putatively inhibitory) neurons and their modulation by anisomycin, a protein synthesis inhibitor implicated in synaptic and functional changes in neurons. Under adaptation, both RS and FS neurons exhibited similar amplitude and comparable proportions of neurons showing shifts greater than 8.98°. However, anisomycin reduced the proportion of large tuning shifts (>8.98°), with a stronger trend in FS cells than in RS neurons. Overall, these results show that adaptation modifies E/I balance in mouse V1 promoting a new equilibrium, while anisomycin-induced protein synthesis blockade preferentially affects inhibitory circuitry. These results provide insight into the mechanisms underlying cortical plasticity and hold translational promise for modulating maladaptive plasticity in the brain.