Spatiotemporal patterns of neuronal electrical activity evoked by stimulation with a focused femtosecond laser

Neuronal networks exhibit spatiotemporal patterns of electrical activity, such as spike location, spike timing, and burst firing among neuronal populations. These spatiotemporal patterns of neuronal activity play important roles in brain function and are modified by external stimuli. Single-neuron stimulation and measurement of neuronal network responses are effective for elucidating information processing in complex neuronal networks. Single-cell stimulation by transient microperforation based on multiphoton absorption using a focused femtosecond laser can potentially stimulate neuronal networks. In this study, we investigated the spatiotemporal patterns of neuronal network activity evoked by a focused femtosecond laser, particularly the firing rates, synchrony of neuronal activity, and bursting properties, using microelectrode array measurements. We observed highly frequent spikes induced by laser irradiation. By comparing the spike patterns induced by electrical stimulation, we found that laser irradiation decreased the synchrony of the neuronal network activity. Moreover, the burst durations in the local areas of the neurons were elongated by laser irradiation. These results suggest that laser-induced stimulation provides a bottom-up approach for investigating functional connectivity in neuronal networks at the single-cell level.