All-or-none disconnection of pyramidal inputs onto parvalbumin-positive interneurons gates ocular dominance plasticity

ABSTRACT Disinhibition is an obligatory initial step in the remodeling of cortical circuits by sensory experience. Our investigation on disinhibitory mechanisms in the classical model of ocular dominance plasticity uncovered an unexpected novel form of experience-dependent circuit plasticity. In layer 2/3 of mouse visual cortex monocular deprivation triggers a complete, “all-or-none”, elimination of connections from pyramidal cells onto nearby parvalbumin-positive interneurons (Pyr➔PV). This circuit plasticity is unique as it is transient, local and discrete. It lasts only one day, and it does not manifest as widespread changes in synaptic strength, rather, only about half of local connections are lost and the remaining ones are not affected in strength. Mechanistically, the deprivation-induced loss of Pyr➔PV is contingent on a reduction of the protein neuropentraxin2 (NPTX2). Functionally, the loss of Pyr➔PV is absolutely necessary for ODP. We surmise, therefore, that this “all-or-none” loss of local Pyr➔PV circuitry gates experience-dependent cortical plasticity.