Controlling Bursting in Cortical Cultures with Closed-loop Multi-electrode Stimulation
J. Neurosci. 25:3 (2005), 680–688. [PubMed] [Preprint (pdf)]
One of the major modes of activity of high-density cultures of dissociated neurons is globally synchronized bursting. Unlike in vivo, neuronal ensembles in culture maintain activity patterns dominated by global bursts for the lifetime of the culture (up to two years). We hypothesize that persistence of bursting is due to a lack of input from other brain areas. To study this hypothesis, we grew small but dense monolayer cultures of cortical neurons and glia from rat embryos on multi-electrode arrays (MEAs), and used electrical stimulation to substitute for afferents. We quantified the burstiness of the cultures’ firing in spontaneous activity and during several stimulation protocols. While slow stimulation through individual electrodes increased burstiness due to burst entrainment, rapid stimulation reduced burstiness. Distributing stimuli across several electrodes, as well as continuously fine-tuning stimulus strength with closed-loop feedback, greatly enhanced burst control. We conclude that externally applied electrical stimulation can substitute for natural inputs to cortical neuronal ensembles in transforming burst-dominated activity to dispersed spiking, more reminiscent of the awake cortex in vivo. This non-pharmacological method of controlling bursts will be a critical tool for exploring the information processing capacities of neuronal ensembles in vitro, and has potential applications for the treatment of epilepsy.