FIGURE 2.

Optokindling via simultaneous EEG recording and ChR2 stimulation in awake behaving animals. (A) Coronal M1 section immunostained for EYFP indicated ChR2 expression in layer 2/3 (L2/3), 5, and 6, though predominantly in L2/3. Inset shows close-up of L2/3 ChR2-expressing PCs. (B) To simultaneously activate ChR2 and acquire EEG, ferrules and recording screws were implanted bilaterally above M1, without penetrating the cortex. Fiber optic cables were air-coupled to 445-nm lasers. EEG signals were processed by an extracellular amplifier, but not pre-amplified. A computer (not shown) TTL-gated the lasers and digitized amplified EEG signals. (C) Sample EEG trace illustrating that M1 optokindling did not elicit seizures in stimulation session 1 of 25 (Top). Spectrogram shows direct light-driven responses in the 50-Hz band but no seizures (Bottom). (D) M1 optokindling in session 13 elicited a prominent seizure in this sample EEG sweep (Top). Spectrogram reveals both light-driven responses in the 50-Hz band as well as increased power in low-frequency bands (Bottom). Reproduced and modified from Figure 1 in Cela et al. (2019), with permission.