Abstract
During development, cortical neurons show highly synchronized spontaneous activity. This spontaneous activity probably reflects the mechanisms underlying proper network formation regulated by activity-dependent synaptic modification. To see long-term transition in this spontaneous activity, we constructed a microelectrode-array (MEA) based continuous monitoring system. Rat cortical neurons were cultured on MEAs with 64 embedded electrodes and maintained in a conventional CO2 incubator. A perfusion system for medium changes and recording setup for electrical signals were directly connected to the MEA in the incubator. Culture medium was continuously perfused at a very slow rate (0.1 ml/h), which was quite effective to keep constant conditions without contamination. Using this system, we succeeded in recording spontaneous activity of cultured cortical networks, almost continuously from 5 days to more than one month in vitro. It was revealed that the spontaneous activity patterns showed transition from simple synchronized bursts to complex mixture of multiple patterns, separated by a brief silent period at approximately 2 weeks in vitro.
