The relation between structure and function at single synapses in the mouse neocortex.

The chemical synapses that neurons use to transmit information between one another are typically analyzed through one of two complementary approaches: Structural analyses, where the high resolution of the electron microscope (EM) is required to resolve details of fine structure, and various functional methods, including electrophysiological or optical recording methods. Correlating structure and function at the level of single synapses is rarely attempted, because of the extreme technical difficulties of recording the physiological responses of single synapses combined with analyzing them structurally using the EM.

We have previously used serial section EM to characterize quantitatively the ultrastructure of identified thalamocortical synapses in the primary motor (M1) and somatosensory cortex (S1) and identified some key structural features that may correlate with the physiology of those same synapses.

In a next step, we will study the physiological responses of pairs of cells that are monosynaptically connected. This will allow us to trigger single action potentials in one cell and measure quantitatively transmission through a single synapse in the other cell. By labeling cells whose synaptic physiology is known, and then making serial section EM reconstructions of the synapses, we hope to discover critical relations between structure and function at individual synapses.