ABSTRACT
Synapses are continually regulated by their own activity. In the neocortex, direct interactions between cortical areas play a central role in cognitive function, but the dynamic regulation of these long-range corticocortical synapses by activity and their impact on a postsynaptic target neuron is unclear. Here, we use an optogenetic strategy to study the connections between mouse somatosensory and motor cortex. We found that short-term synaptic facilitation was strong in both corticocortical synapses, resulting in far more sustained responses than local intra-cortical and thalamocortical connections. This facilitation was dependent on the presynaptic calcium sensor synaptotagmin-7 and altered by several optogenetic approaches. Recordings revealed that during repetitive activation, the short-term dynamics of corticocortical synapses enhanced the excitability of layer 2/3 pyramidal neurons, increasing the probability of spiking with activity. Furthermore, the properties of the connections linking primary with secondary somatosensory cortex resemble those between somatosensory-motor areas. These results reveal a synaptic mechanism by which corticocortical projections may mediate specific changes in cellular excitability over relatively extended periods.
Competing Interest Statement
The authors have declared no competing interest.
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