High-speed, high-resolution epifluorescence imaging system using CCD sensor and digital storage for neurobiological research

We have designed and built a high-speed CCD imaging system for monitoring neural activity in an exposed animal cortex stained with a voltage-sensitive dye. Two types of custom-made CCD sensors were developed for this system. The type I chip has a resolution of 2664 (H) × 1200 (V) pixels and a wide imaging area of 28.1 × 13.8 mm, while the type II chip has 1776 × 1626 pixels and an active imaging area of 20.4 × 18.7 mm. The CCD arrays were constructed with multiple output amplifiers in order to accelerate the readout rate. The two chips were divided into either 24 (I) or 16 (II) distinct areas that were driven in parallel. The parallel CCD outputs were digitized by 12-bit A/D converters and then stored in the frame memory. The frame memory was constructed with synchronous DRAM modules, which provided a capacity of 128 MB per channel. On-chip and on-memory binning methods were incorporated into the system, e.g., this enabled us to capture 444 × 200 pixel-images for periods of 36 seconds at a rate of 500 frames/second. This system was successfully used to visualize J neural activity in the cortices of rats, guinea pigs, and monkeys.