Chronic imaging of cortical sensory map dynamics using a genetically encoded calcium indicator

2 Centre of Molecular Physiology of the Brain (CMPB) at University Medicine GDepartment of Neurology, GGermany Non-technical summary Optical imaging is widely used to map functional areas of the cerebral cortex. We present a method for fast fluorescence imaging of map-level cortical activity using a calciumindicatorprotein.Sensory-evokedneuronalactivitycanbeimagedrepeatedlyinthesame mouseover weeks, enablingnew opportunitiesforthe longitudinalstudyof corticalfunctionand dysfunction. We hope this method will be flexibly applied across different cortical areas and to a variety of newly developed genetically encoded calcium and voltage sensors. Abstract In vivo optical imaging can reveal the dynamics of large-scale cortical activity, but methodsforchronicrecordingarelimited.Herewepresentatechniqueforlong-terminvestigation of cortical map dynamics using wide-field ratiometric fluorescence imaging of the genetically encoded calcium indicator (GECI) Yellow Cameleon 3.60. We find that wide-field GECI signals reportsensory-evokedactivityinanaesthetizedmousesomatosensorycortexwithhighsensitivity and spatiotemporal precision, and furthermore, can be measured repeatedly in separate imaging sessions over multiple weeks. This method opens new possibilities for the longitudinal study of stability and plasticity of cortical sensory representations.