UC San Diego

Sensory representations in the cortex adapt during experience and learning to shape perception. Behaviorally relevant stimuli strengthen and expand within cortical sensory maps, while irrelevant or unused stimuli weaken and shrink. These changes in maps are known to include modifications of excitatory neurons and circuits, but it remains uncertain how inhibitory plasticity may be involved. This thesis investigates the cellular basis for experience-dependent plasticity of feedforward inhibition within layer 2/3 (L2/3) of rodent somatosensory cortex and addresses how changes of excitatory and inhibitory circuits are coordinated during map plasticity. Experiments revealed that sensory deprivation weakens feedforward inhibition onto L2/3 excitatory pyramidal cells via local fast-spiking (FS) interneurons. This weakening reflected reduced excitatory synaptic input to FS interneurons, partially offset by increased strength of unitary FS to pyramidal cell synapses. These changes occur in parallel with previously reported decreases of feedforward excitation onto L2/3 pyramids and preserve mean excitatory-inhibitory balance during experience- dependent plasticity