A second-generation imaging system for freely moving animals

An updated image sensor to be used in a miniature microscope system for recording brain activity over a wide cortical area (4–9 mm
²
) is presented. The image sensor is a 100 × 100 pixel array fabricated in bulk CMOS process. The sensor also contains a 10-bit ADC and two input channels to measure other physiological signals concurrently with the optical data. Another feature of the image sensor is the ability to observe dF over sequential frames in hardware, in order to reduce the amount of data that must be read out of the image sensor at high speeds. The speed and noise performance of the image sensor is suitable for voltage-sensitive optical probes in small systems for awake and freely moving animals.