Spike-timing dependent plasticity changes responses of cortical neurons from sub- to supra-threshold in vivo

A broad range of visual stimuli generate synaptic input to visual cortex neurons, whereas only a small selection of stimuli generates action potential output from the neuron, that informs downstream targets of the sensory event - but whether plasticity rules can predictably change the spiking response of a neuron by changing a subthreshold response into a suprathreshold response, although proposed, is unclear. Here, we show that a brief spike-timing dependent plasticity (STDP) protocol consisting of close timing of postsynaptic action potentials (APs) and presynaptic inputs derived from visual stimulation can convert subthreshold responses into suprathreshold responses and restructure the neuron's suprathreshold receptive field. This reorganization of spiking responses was paralleled by a change in the time course of the subthreshold voltages and was abolished when muscarinic acetylcholine receptors were blocked. Computational simulations, based on in vitro STDP data, could reproduce the subthreshold membrane potential changes reported here, only when temporal jitter, based on in vivo data, was included during pairing at the presynaptic input stage. Together this shows that timing based plasticity rules, using 10’s postsynaptic spikes, has a functional impact on the spiking response patterns of sensory neurons in vivo by changing suprathreshold tuning properties of the visual cortex neurons