Synaptic Interactions in Assemblies of Cultured Aplysia Neurons. I: Analysis of Optically Recorded Electrical Activity

We constructed ensembles of Aplysia LUQ neurons in culture. These cells form chemical connections and may couple electrotonically. Their electrical activity was measured with multisite optical recording techniques and voltage sensitive dyes (Parsons et al., Biophys. J., July 1989). These Techniques allowed us to record for prolonged periods with a good signal-to-noise ratio and negligible phototoxicity (2 hr, S/N = 10). However, the extensive outgrowth of the neurons caused each detector to monitor the activity of many cells. We show how individual spike trains were reconstructed from the spatial distribution of timing and amplitude information in the optical records. The effective connectivity was determined from the spike trains. Weak interactions could be deduced from repeated measurements.