Development of 50 x 50 fiber-array photodiode camera

摘要

Optical imaging of neural network activity using voltage sensitive dyes is expected to be easier than the current electrode method to get multiple point information simultaneously. A high-speed camera is needed to capture a change of a fluorescence image caused by a potential change accompanying neuronal activity. The electrical excitation of a neuron lasts for a few milliseconds and the concomitant fluorescence change is reported to be a few percent or less of its total intensity. A 50 $MUL 50 photodiode camera is specifically designed for this purpose. This camera can take pictures with a 12 bit accuracy every 256 $mu@s for about 1 sec(4096 pictures). The epi-illuminated fluorescence image through an objective lens is focused on the end-plate of a 50 $MUL 50 plastic optical fiber bundle. Individual photodiodes and ac-coupled amplifiers are connected to each optical fiber. The time-dependent portion of each signal is transferred to one of the ten 12-bit AD converters through a three-stage multiplexer, and digitally stored in a 20 MBytes RAM. We demonstrated the ability of the camera by capturing membrane potential images of sea urchin eggs induced by an external electric field.