BME Frontiers / 2020 / Article / Fig 1

Review Article

From Neurons to Cognition: Technologies for Precise Recording of Neural Activity Underlying Behavior

Figure 1

Technologies for recording neuronal activity in rodents. Calcium imaging, voltage imaging, and electrophysiological recordings are three key approaches to measure neuronal activity in rodents. (a) Calcium imaging involves the expression of a fluorescent calcium sensor (GCaMP family shown here), for example, through viral injections in the brain. The fluorescent signal can be monitored through single-photon or two-photon microscopy in freely moving as well as head-fixed animals. Fluorescence intensity traces of neurons reflect their action potential firing. (b) Voltage imaging uses a similar approach by expressing fluorescent genetically encoded voltage indicators instead of calcium sensors. The schematic of ASAP family sensors is shown here. Fluorescence intensity directly indicates neuronal membrane voltage revealing spiking and subthreshold activity. (c) Electrophysiological recordings represent the most direct measure of neuronal activity. Microwire or silicon-based electrodes are implanted into the brain and record voltage changes in freely behaving (shown here) or head-fixed animals. A wide variety of probe designs exist with different geometric shapes and different number of recording channels. Signal traces from electrophysiological recordings need to be computationally associated to individual neurons through spike sorting.