Fig. 1

Surgical electrode implantation and headset assembly. Shown is an illustration of a set of epidural screw electrode placement in a P35–40 rat. A The five screw electrodes include two frontal (F3: left frontal, F4: right frontal, 2 mm anterior, and 3 mm lateral to the bregma), two parietal (P3: left parietal, P4: right parietal, 5 mm posterior, and 3 mm lateral to the bregma) and one anterior reference electrode (Ref, midline and 6 mm anterior to the bregma). The coordinates are based on the Sherwood and Timiras stereotaxic atlas of the developing brain. A sixth electrode consists of a free wire placed under the neck’s skin and serves as a ground electrode. Before initiating the surgery, all five screw electrodes and the ground one are soldered to golden plated sockets (black arrow) via an insulated copper wire. The wires are lightweight and moldable in various shapes which facilitates handling during surgery and giving the headset its final shape. B Shown is the 6-channel plastic pedestal (white arrow) that accommodates the 6 electrode sockets. After placing the sockets in their respective ports, the pedestal is pushed down while tucking in the copper wires in order to form a compact headset. C Dental cement is poured from the sides using a syringe, while still in a semi-liquid form in order to allow infiltration of all the gaps between the wires and pedestals. This gives the protective headset its final form that keeps all the elements together, and protects the skull, without requiring sutures. D After 5 days of postoperative resting, the headset is connected to the EEG cables (white arrow) ending with 6 pins that fit into the pedestal on the headset. The 6 pin EEG cable, a pedestal, and a screw electrode connected to a socket, are shown next to each other for illustrative reasons