Generation of far field potentials from the trigeminal nerve in the cat

This study provides evidence that far field potentials (FFPs) are generated from the trigeminal nerve in the cat. By stimulating the main mental nerve, three components (component 1, 0.59 ± 0.06 ms; component 2, 0.81 ± 0.06 ms; and component 3, 0.98 ± 0.07 ms) were identified from surface electrodes. These three components were thought to be positive and negative FFPs because each component had a stationary peak and was distributed on the head being divided into positive and negative fields. Results of a study of lesions and recording compound action potentials (CAPs) defined the neural origins of those potentials as follows: component 1, the mandibular nerve at the mandibular foramen; component 2, the mandibular nerve at the foramen ovale; and component 3, somewhere between the gasserian ganglion and the trigeminal root. The amplitude of component 2 decreased when the mandibular nerve at the foramen ovale was immersed in cerebrospinal fluid (CSF) after opening the foramen and recovered to the prior level after closing the foramen with beeswax. We concluded that this transformation resulted in the change in electrical resistance of the volume conductor around the nerve.