This article details a surgical procedure for inserting microelectrodes into the brain of an anesthetized mouse to record local field potentials (LFPs). The methodology ensures accurate placement and reliable data acquisition for studying neural activity.
Begin with an anesthetized mouse with its head secured in a stereotactic frame.
Shave and sterilize the scalp.
Make an incision and remove the residual tissue to expose the skull.
Clean the skull with a disinfectant and drill holes at the target locations.
Remove the outer layer of the brain.
Insert microelectrodes filled with an ionic solution into the holes at a desired angle.
Lower both microelectrodes into the target coordinates of the brain.
Test the electrodes' resistance and adjust the recording settings to ensure the reliable acquisition of local field potential or LFP data.
LFP reflects voltage changes resulting from the collective activity of many neurons within a small region.
Record LFPs from both hemispheres to compare the neural activity between them.
Prior to surgery, confirm the depth of anesthesia of the mouse by performing a tail or toe pinch with forceps. Next, position the mouse in a stereotaxic apparatus, and fix its head. Apply ointment on both eyes to keep them moist.
Then, shave the head and sterilize the area. Make a small incision of 12 to 15 millimeters in the middle of the shaved area. Using forceps, gently pull the scalp away from the midline. Afterward, separate the skin gently, and remove the residual tissue.
Clean the skull using hydrogen peroxide-coated cotton buds. Under a stereomicroscope, drill two small holes of 1- to 1.5-millimeter radii on both the left and right sides of the skull to allow insertion of the recording microelectrodes into the M2 regions.
Carefully, remove the dura mater with a tungsten needle, then, insert two separate recording microelectrodes filled with 0.5 molar sodium chloride into the holes at an angle of 60 degrees using mechanical micromanipulators.
For LFP recording, slowly lower the left and right glass electrodes to the M2 coordinates. For quality control, test the resistance of each electrode using the differential amplifier. Next, set the recording process at 0.1 Hertz high-pass and 1,000 Hertz low-pass with 1,000 times amplification. Collect the digitized raw LFP data in stable state for at least 60 seconds, with the mouse breathing evenly at two breaths per second under anesthesia.
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