Retinal ganglion cells transmit visual scene as an action potential to visual cortex through optic nerve. Conventional recording method using single intra- or extra-cellular electrode enables us to understand the response of specific neuron on specific time. Therefore, it is not possible to determine how the nerve impulses in the population of retinal ganglion cells collectively encode the visual stimulus with conventional recording. This requires recording the simultaneous electrical signals of many neurons. Recent advances in multi-electrode recording have brought us closer to understanding how visual information is encoded by population of retinal ganglion cells. We examined how ganglion cells act together to encode a visual scene with multi-electrode array (MEA). With light stimulation (on duration: 2 sec, off duration: 5 sec) generated on a color monitor driven by custom-made software, we isolated three functional types of ganglion cell activities; ON (35.0±4.4%), OFF (31.4±1.9%), and ON/OFF cells (34.6±5.3%) (Total number of retinal pieces = 8). We observed that nearby neurons often fire action potential near synchrony (＜1 ms). And this narrow correlation is seen among cells within a cluster which is made of 6∼8 cells. As there are many more synchronized firing patterns than ganglion cells, such a distributed code might allow the retina to compress a large number of distinct visual messages into a small number of ganglion cells.

KeywordsRetinal ganglion cell, Multichannel recording, ON cell, OFF cell, ON/OFF cell, Synchronized firing