Subcellular synaptic connectivity of layer 2 pyramidal neurons in the medial prefrontal cortex

Pyramidal neurons in the prefrontal cortex (PFC) are important for the control of cognitive and emotional behavior. The medial PFC (mPFC) receives diverse long-range excitatory inputs from the midline thalamus, contralateral mPFC, basolateral amygdala, and ventral hippocampus. While axons from these different regions have distinct distributions in the mPFC, their functional connections at the cellular and subcellular levels remain unknown. Here, we use optogenetics to show that layer 2 pyramidal neurons in acute slices of the mouse mPFC receive excitatory inputs from each of these regions. Using a combination of optogenetics and two-photon microscopy, we then determine the subcellular properties of these inputs. We find that different types of inputs make selective contacts at the levels of both dendrites and spines. Using two-photon uncaging, we show that this subcellular targeting strongly influences synaptic efficacy in these neurons. Together, our results show that functional connectivity is finely tuned, with important implications for signal processing in the mPFC.