Multi-site Stimulation Quiets Bursts and Enhances Plasticity in Cultured Networks
33rd Annual Meeting of the Society for Neuroscience, New Orleans, LA, 2003
We study stimulus-induced plasticity and information processing in dense dissociated monolayer cultures of E18 rodent cortical neurons grown on Multi-electrode arrays (MEAs). Dishwide spontaneous bursts, or “barrages” dominate the activity of such networks. We hypothesize that these spontaneous barrages are due to lack of natural input and are wiping out the effects of potential plasticity-inducing stimuli. We compensate for the absence of natural input by applying a continuous stream of weak electrical stimuli at multiple electrodes. With such distributed sequential stimulation, we have successfully reduced the contribution of spontaneous barrages to the total firing rate of the network. The goal of this work is to investigate whether such controlled cultures are more conducive for the induction of plasticity at the network level. A 10-Hz sequence of stimuli applied at 10 electrodes reduced the duration and rate of occurrence of barrages. With this ’quieted’ level of activity as baseline, a tetanic pulse train is applied to two other electrodes, which induces a spatially distributed pattern of LTP and LTD. We study the temporal structure of spike trains and the activity-dependent changes in the reliability and reproducibility of spike patterns evoked by a probe stimulus. We use these patterns in the control of animats or hybrots (hybrid neural-robotic creatures). We find that in cultures controlled by continuous background stimulation throughout the experiment, tetanic stimulation induces a stronger and more sustained change in probed response. Changes in neural plasticity can be mapped to changes in the animat’s behavior, enabling us to study how information is encoded within an embodied living neural network.