Morpho-Functional Mapping of Cortical Networks in Brain Slice Preparations Using Paired Electrophysiological Recordings

The study of neuronal microcircuits with paired electrophysiological recordings from synaptically coupled neurons in brain slices has revealed a large variety of neuronal cell types with highly distinct and connection-specific characteristics of synaptic transmission. In combination with simultaneous biocytin fillings paired recordings permit correlated structural and functional analyses of pre- and post-synaptic neurons, including technically challenging approaches such as a quantal analysis of identified unitary synaptic connections. Here, we present the technical procedures for successful paired recordings, methods to obtain an optimal neuronal morphology, the working principle for neuronal reconstructions, and the basis and caveats in estimating neuronal connectivity from paired recording data. The paired recording technique will remain an important approach in the analysis of neuronal connectivity in the brain, in particular with respect to the finer details of synaptic transmission, since it allows the morphological and functional characterisation of both pre- and post-synaptic neuronal cell types which are not possible using other methods to study neuronal connectivity.