Synaptic Plasticity and Excitatory-Inhibitory Balance in the Auditory Cortex

Activity-dependent synaptic plasticity refers to a set of mechanisms and organizing principles that modifies the strengths of synapses in neural circuits. Over the past decades, most studies have examined excitatory synapses, as the strength and organization of these synapses dictates information flow and processing in the mammalian central nervous system. However, excitation must be appropriately regulated by inhibition to ensure that networks are neither hyper- nor hypo- excitable. As excitatory synapses can be rapidly and persistently modified, inhibitory synapses also must be plastic for dynamic control of overall excitatory-inhibitory balance. In this thesis, I describe coordinated modifications to excitatory and inhibitory synapses onto the same postsynaptic neurons in the mouse auditory cortex. Excitatory and inhibitory synaptic plasticity both depend on the timing between pre- and postsynaptic action potential firing, but the precise temporal requirements and learning rules are different. I also examine mechanisms and functional consequences of plasticity of cortical excitatory-inhibitory balance. These studies constrain the requirements for synaptic plasticity in the auditory cortex and demonstrate how initially unrelated inputs can become bound together by controlling postsynaptic spike generation.