Pain Relief In Humans Research Articles

Escape from and avoidance of nociception elicited by intracranial stimulation of the cat subthalamus

An investigation was undertaken to find out whether cats would learn by a non-aversive auditory cue to avoid a pain-producing intracranial stimulation (ICS) of the subthalamic region. The purpose was to determine whether such ICS produces genuine pain or simply generalized evasive actions. Bipolar stimulating electrodes were implanted bilaterally [into the brain, aimed at] in the H2 (lenticular fasciculus)-H (prerubral) fields of Forel or adjacent part of the zona incerta. The animals were trained initially to escape noxious ICS and, subsequently, to avoid that same noxious ICS when presented with an auditory cue which preceded the ICS by 10 s. After training, lesions were produced through the same electrodes; controls were without lesions. After recovery, both groups were taken through the same escape and avoidance sequence. In eight animals the prelesion avoidance patterns were not significantly altered and remained intact throughout the postlesion testing period. The effective electrode placements extended through the subthalamus to the ventral part of the rostral mesencephalic tegmentum. Fiber projections, with or without terminals, were found in the zona incerta, H1 field, lateral, posterior and dorsal hypothalamus, intralaminar, ventral, and midline thalamic nuclei, and rostral mesencephalic central gray. Certain effective stimulating or ablative neurosurgical procedures for relief of pain in humans are largely consistent with these findings.