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Ghazaleh Afshar 1,3,*, Ahmed El Hady 1,2,3,*, Oliver Schlueter 5, Walter Stuehmer 2,3,4, Fred Wolf 1,3,4 1.Max Planck Institute for Dynamics and Self organization, Goettingen, Germany. 2.Max Planck Institute of Experimental Medicine, Goettingen, Germany. 3.Bernstein focus for Neurotechnology, Goettingen, Germany. 4.Bernstein center for computational neuroscience, Goettingen, Germany. 5.European Neuroscience Institute, Goettingen, Germany. It is known that in vivo and in vitro neural systems are able to adapt to stimuli with different features. By using a combined multielectrode array - optogenetic technology, we stimulate and record from neuronal cultures expressing channelrhodopsin2. We studied the adaptation of neurons stimulated by whole field blue light illumination. When the neuronal network was stimulated with 40 constant blue light pulses of length 1s separated by 100 ms, we observed an acute photoresponse during each stimulation pulse that rapidly decayed as the average firing rate is strongly adapting. We did not observe any immediate off response or adaptation current after the end of the 40 stimulation pulses. We observed that an adaptation time constant of 500 ms which is longer than the desensitization time constant of the photosensitive channel (50 ms) reflecting an adaptation mechanism intrinsic to the network. Interestingly, after turning off the stimulus, the network slowly switched into an ongoing state of bursting activity. We conclude that light stimulation can be successfully used to study adaptation and state switching in biological neuronal networks. * Equally contributed to the work |
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