Abstract
Using the combination of a voltage-sensitive fluorescent dye and high luminance light emitting diodes (LEDs) for a light source, we have developed an optical recording system for neural activity from 1020-site in the intact rat cerebral cortex. Green LEDs provide an excitation light, and the fluorescent light from the stained preparation formes a magnified real image by a tandem lens optic system. The fluorescent light intensity at the image plane is detected simultaneously by a 34 x 34-element photodiode array (PDA). The outputs from PDA are amplified, multiplexed and digitized at a time resolution of 1 msec for each pixel. Data are sent to a computer and stored in a high-speed hard disk unit. Since the data storing speed is greater than the data transferring speed, we succeed in continuous recording on hard disk in real time. Now, the longest recording time is about 1000 sec. This restriction is simply owing to the maximum size of one file, 2 GB. We applied this system to the rat primary somatosensory cortex (Sm1). The cortex was stained with RH414 and placed under the optical apparatus. When the foot was electrically stimulated, optical signals from the hindlimb region had a small deflection with similar latency to that of the evoked potential. We consider this signal as representing the neural response of Sm1. Though the artifact derived from heartbeat was large, we could detect the neural response optically in a single sweep, if the stimulating pulse was given between the pulsations where the artifact was relatively small. [Jpn J Physiol 55 Suppl:S141 (2005)]
