Postnatal maturation of cortical microcircuit function in barrel cortex

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The rodent barrel cortex serves as a model system for investigating sensory processing and sensorimotor integration in the mammalian neocortex. A promising approach to gain insights into the functional organisation of the neuronal microcircuit in barrel cortex is to study postnatal maturation in juvenile animals and relate it to the development of behaviour. In the coming years we aim to elucidate the functional maturation of neuronal network activity in the superficial layers of mouse barrel cortex during postnatal development employing state of the art in vivo imaging techniques. We will focus on postnatal weeks 2 and 3, a critical time period during which mice begin to explore their environment and start active whisking behaviour. We aim to dissect the contributions of single-cell and network mechanisms underlying functional changes during this period, in particular the role of different interneuron subtypes and the stabilization of the excitation to inhibition ratio and its dependence on sensory input. We also aim to discriminate subpopulations of output neurons that project to either primary motor cortex (M1) or secondary somatosensory area (S2), in order to reveal how corticocortical activation patterns develop. Because longitudinal, chronic calcium imaging in juvenile mice turned out to be difficult, we will focus on acute calcium imaging experiments, combined with transgenic mice, electrophysiology and post-hoc immunostaining. While basic properties of spontaneous and whisker-evoked activity of single cells and local neuronal populations will be studied during anaesthesia, we will also attempt to measure network dynamics in awake juvenile mice during voluntary active whisking, thus directly linking the maturation of circuit dynamics to this emerging prominent behaviour.