Chronic Implantation of Whole-cortical Electrocorticographic Array in the Common Marmoset

This protocol demonstrates the implantation of an electrocorticographic array onto the cortex of a non-human primate. To shed light onto large scale information processing in primate shift neuroscience. The main advantage of this technique is that it provide an opportunity for monitoring large scale cortical activity with high spatial temporal resolution.

Begin by making a four centimeter skin incision through the midline of the scalp. Use a curet to detach the temporal muscle from the skull until the entire surgical area is exposed. And clear any tissues from the skull surface.

Stop the bleeding completely with pressure hemostasis or bone wax as necessary. Wrap the edge of the skin and muscles with moistened gauze. And place the frontal edge of the array onto the edge of the frontal pole.

Use a pencil to mark the area for the planned craniotomy, slits and holes on the skull. And position the dissecting microscope over the surgical area. Drill the craniotomy along mark one.

While drilling, blow air at the cutting edge to maintain a clear view for the surgeon, cutting the bone all the way around mark two as the bone piece will still be attached to dura at the center. Slowly and carefully, lift the piece up from one edge. And peel off the dura with a spatula.

Remove the bone tips from the bone piece and keep the bone wrapped in moistened gauze until it is returned to the skull at the end of the procedure. Drill at marks three and four to allow the insertion of electrodes into the orbital, frontal, and occipital areas, respectively. Drill slits on mark five to allow confirmation if the array is properly inserted.

The dura will now be exposed. Wash the the area with saline and stop bleeding with pressure hemostasis and a gelatin sponge as necessary. Clean the edge of the open craniotomy if needed and make the mark six slits into which the reference electrodes will be placed.

Inserting a spatula under the skull to protect the dura matter, use a one millimeter screw to drill screw holes at four points around each stem of the connector. And install peak screws as anchors to fix the connector to the skull. Then, using flathead forceps to hold the array, insert the electrocardiographic array into the epidural space.

Place the reference electrodes in the epidural space. Then apply dental acrylic to the reference. Place the ground electrodes on the cranial surface.

Then apply dental acrylic to the ground electrode. Put the bone piece back in place, and apply dental acrylic to the screws to fix the connector and head post to the skull. Then, use a 6 O nylon suture to close the skin at the forehead and at the rear of the end.

And use skin closures to fix the skin to the sides of the connector. Here, examples of auditory evoked potentials from multiple auditory areas in an awake marmoset are shown. During exposure to randomized pure tones with 20 types of frequency, different wave forms can be observed from lower and higher auditory areas, indicating that the spatial resolution of the electrocardiographic array can capture different information processing in different cortical areas.

Option can be virally transduced in the marmoset brain because electrical implantation to enable long term chronic photo stimulation and simultaneous monitoring of the cortical responses.