Evoked potential mapping of the rostral region by frameless navigation system in Mexican hairless pig

There is an increasing need for a pig model for use in functional brain studies, but a system for determining precise stereotactic coordinates has yet to be developed. Thus, we devised a frameless navigation system for stereotactic positioning, and measured coordinates for the rostral region and the primary somatosensory cortex in the pig brain. Raw coordinates for somatic evoked potential recordings were obtained by passive optical tracking. The location was registered to a computed tomographic image in reference to four stable skull landmarks: the upper margin of each auditory meatus, the external occipital protuberance, and the point where the interfrontal suture crosses a line drawn between the two supraorbital foramina (“IF” point). The cortical position with the greatest response in evoked potential was mapped −51.0 ± 4.67 mm rostro-caudally, 9.1 ± 1.19 mm medio-laterally, and −8.8 ± 0.48 mm dorso-ventrally (means ± SD; n = 3) to the IF point. These results show that frameless registration is useful for coordinate-based evoked-potential mapping of the rostral region of the Mexican hairless pig.

► We tested the optical tracking system in the brain of Mexican hairless pig.
► Some landmarks were chosen and set on skull structures to get coordinates.
► Somatic evoked potentials (SEPs) were recorded in the primary sensory cortex.
► Coordinates were given for recording the largest SEP with much less variation.
► We show the utility of a new frameless registration method for the spatial mapping.