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Mapping dEndritic inforMation prOcessing in behaving mice using simultaneous spatio-tempoRal voltage and calcium Imaging and wholE-cell electrophySiology

Periodic Reporting for period 1 - MEMORIES (Mapping dEndritic inforMation prOcessing in behaving mice using simultaneous spatio-tempoRal voltage and calcium Imaging and wholE-cell electrophySiology)

Reporting period: 2020-01-01 to 2021-12-31

This fellowship aimed to use a novel simultaneous dendritic voltage and calcium imaging and whole-cell recording technique to investigate dendritic processing in behaving mice. We aimed to investigate how spatio-temporal processing of dendritic signals convey sensory information and relate to learning, specifically the role of back-propagating action potentials for memory formation. To do this a sensory stimulus, such as a whisker deflection, would be used to evoke somatic and dendritic signals in individual neurons. Spatio-temporal dendritic voltage and calcium maps and somatic signals would be simultaneously recorded. Dendritic signalling maps recorded during sensory stimulation would be compared to signal maps of spontaneous activity, and also monitored during behavioural training (such as learning the water reward task). Mouse behaviour would also be recorded (using high speed cameras and water spout licking sensor, for example). Simultaneous whole-cell electrophysiology was planned to detect somatic action potentials, and by comparison with spatio-temporal dendritic voltage and calcium maps, back-propagating signals detected and their characteristics during mouse behaviour would be examined.
The first 6 months of the fellowship were allocated for method development, setup optimization and preliminary data acquisition. It was not possible to implement all the planned tasks and achieve the objectives of the project, due to the full and partial closure of the host premises for Covid-19 pandemic in the period March-June 2020 and to the early termination of the fellowship from 01/07/2020.

Work completed included gaining laboratory training in surgeries, behavioral training and in using laboratory equipment. An ‘Introductory Course in Laboratory Animal Science’ was completed, and a two-photon microscope was re-built and optimized while at EPFL.
Spatio-temporal voltage and calcium dendritic mapping has so far only been applied to cerebellar Purkinje neurons in awake resting mice. Therefore, this fellowship was expected to develop and utilize novel voltage imaging techniques to explore dendritic processing of layer 2/3 Pyramidal neurons in the primary somatosensory barrel cortex during behavioural training in mice.