We fabricated a silk-based low-impedance flexible electrode by coating a silk thread with the electroconductive polymer poly(3,4-ethylenedioxythiophene) doped with p-Toluenesulfonate (PEDOT:pTS). This electrode had a lower impedance (about 1.8 kΩ/cm) than the silk electrode coated with PEDOT doped with poly(styrene sulfonate) (PEDOT:PSS) (about 1.3MΩ/cm) reported previously. Using this electrode, a novel gamma-band oscillatory activity was recorded in the electrocorticogram from the embryonic chick brain with a high signal-To-noise ratio. Electrical stimulation was also possible with the silk electrode. We also fabricated an all-silk electrode array and recorded synchronized gamma oscillations. These results demonstrate that the silk electrode can be used for electrophysiological recording and local stimulation in vivo. The silk electrode has the potential to be used for diagnostic and therapeutic purposes and as a brain-machine interface.