To understand cortical functions, it is essential to determine how information contained in sensory input is represented and processed in individual cortical neurons that are morphologically and neurochemically diverse. To understand mechanisms underlying the representational and processing properties of individual cortical neurons, a blind, in vivo, whole-cell patch-recording technique has been applied to examine sensory-driven excitatory and inhibitory synaptic inputs onto cortical neurons. Results from such studies have provided new insights into synaptic circuit mechanism underlying cortical neurons'response properties. Although this technique can be combined with post hoc histological methods to reconstruct the morphology of recorded cells, its blind nature largely limits its potential in examining various cell types in the cortex, since it normally results in a biased sampling of excitatory pyramidal neurons in the cortex. In this exploratory project, we will study a new technique for revealing functional properties and synaptic inputs of inhibitory cortical neurons in vivo, two-photon imaging guided patch recording (TPGP) in which fluorescently labeled neurons are visualized by two-photon imaging and specifically targeted for patch recording. This technique has benefited from recent development of mouse genetics in labeling cells of specific types with fluorescence proteins such as green fluorescence protein (GFP), with their expression controlled by cell-type specific promoters. At an initial step, we will apply this recording technique to GFP-labeled GABAergic interneurons in the supragranular layers (L1-3) of mouse primary visual cortex (V1), to address the receptive field properties of these neurons and how these properties are determined by the integration of visually activated excitatory and inhibitory synaptic inputs.
