Imaging of cortical neuronal-activity with red-shifted functional indicators during motor task execution

Intracellular free calcium ions concentration in neuronal population can be longitudinally evaluated using fluorescent protein indicators, such as genetically encoded calcium indicators (GECIs). In detail, GECIs with long emission wavelengths are particularly attractive for deep in vivo tissue microscopy. Red-shifted GECI have the additional advantage of avoiding spectral overlap with commonly used neuronal actuators (Channelrhodopsin). Here we screen few-selected red-shifted GECI to perform in vivo study of mouse cortical-activity during motor task execution. To that end, wide-field fluorescent microscopy and a robotic mouse platform have been combined for simultaneous recording of both cortical neuronal-activity and force applied by its contralateral limb. At first, four different GECI have been tested. Once identified RCaMP1a as the best indicator in terms of transfection extension and sensitivity, we used this construct to analyze cortical neuronal activity at primary motor cortex level during mouse’s learning and execution of a forelimb-pulling task in a robotic device. Our results showed that RCaMP1a can be successfully used to perform longitudinal imaging of awake mice.