A further examination of effects of cortical stimulation on primate spinothalamic tract cells

Abstract

1. Stimulation of the sensorimotor cortex was found to excite and/or inhibit nociceptive spinothalamic tract cells. Thirteen wide dynamic range cells were inhibited by cortical stimulation, 6 were excited and 14 were both excited and inhibited. Four of six high-threshold cells were excited and one was inhibited. 2. Intermediate (200 ms) or long (2 s) duration conditioning trains were effective in reducing responses of spinothalamic cells evoked by noxious mechanical or thermal stimuli and by A- and C-fiber volleys in the sural nerve. Preferential inhibition of low-threshold responses with little or no effect on high-threshold discharges was observed in some cases. 3. Inhibitory actions were obtained primarily from stimulation of the SI sensory cortex and area 5, while excitation or excitation followed by inhibition was the dominant effect from motor cortex (area 4). Spinothalamic cells were also excited by stimulation of the medullary pyramid. 4. In eight animals extensive mapping of the sensorimotor cortex showed that for a given cell, stimulation of the sensory cortex produced inhibition while stimulation of motor cortex resulted in excitation. 5. The average latency of inhibition from sensory cortex was 29.8 +/- 10 ms, while the average latency of excitation from motor cortex was significantly shorter, 13.5 +/- 9 ms. The shortest latencies for excitation from pyramidal stimulation in the cases evaluated ranged from 2 to 9 ms. 6. Spinal cord lesions were made in five animals to determine the descending pathway(s) mediating corticofugal effects. Cortical and pyramidal effects were eliminated or considerably reduced by lesions involving the dorsal part of the lateral funiculus. This observation combined with latency data suggest that the corticospinal tract may be involved in the mediation of cortical excitation, while both pyramidal and extrapyramidal pathways are likely to be involved in cortical inhibition.

Relief of postoperative pain with jaw relaxation, music and their combination

“…Concurrent reductions in pulse and respiration in this study indicate that relaxation or distraction reduces sympathetic activity as they reduce pain. In addition, music is known to stimulate the sensory cortex and the thalamus which have been found to inhibit nociceptive neurons in the spinal cord (Vidal and Jacob, 1980;Andy, 1983;Dickenson, 1983;Yezierski et al, 1983), and has been found to increase immune factors (Lane and Olness, 1991). Sears and Carroll (1998) have questioned the clinical significance of small differences between relaxation and control groups in pain studies.…”

Relaxation and music reduce pain following intestinal surgery

“…Reduced muscular and mental tension also decrease sympathetic stimulation of the hypothalamus (Beary & Benson, 1974). These processes inhibit transmission of afferent noxious impulses in the central nervous system by activating endogenous opiates, descending nerve impulses, and neuropeptides in the brain and spinal cord (Andy, 1983;Yezierski, Gerhart, Schrock, & Willis, 1983). Recent imaging studies showed that distraction decreased reported sensory pain and also modulated activity in the sensory cortex, while verbal suggestions decreased reported affective pain and also modulated activity in the anterior cingular cortex (Rainville, Carrier, Hofbauer, Bushnell, & Duncan, 1999).…”

Thalamic ventrobasal stimulation for pain relief: probable mechanisms, pathways and neurotransmitters

“…The clinical data we reported 27 , however, strongly suggest that if VB stimulation really inhibits DH nociceptive neurons, this mechanism should play at most a partial and not the most important role in the pain relief accomplished by this procedure. 30 suggested that the inhibitory effects of SI stimulation on the DH nociceptive neurons could be mediated by both corticospinal and extrapiramidal tracts. Based on these findings, Gerhart et al 11 proposed that VB stimulation produces pain relief by activation of these corticofugal pathways.…”

“…There is also experimental evidence against this hypothesis: A) Aiko et al 2 demonstrated increase in local glucose utilization in SI, but not in the DH, following VB stimulation, B) SI stimulation inhibits preferentially DH nociceptive neurons responses to innocuous stimuli while VB stimulation has no preferential effect, although DH nociceptive cells responses to C fiber volleys are reduced to a greater extent than their responses to A fiber volleys 11,30 , C) SI stimulation ipsilateral to an spinothalamic tract neuron produces only weak inhibitory effects, while ipsilateral VB stimulation usually causes a powerful inhibition 11 and D) Inhibition of the responses of spinothalamic cells to noxious stimuli following VB stimulation is observed even when SI stimulation fails to inhibit the responses of the same cells to such stimuli 11 .…”

“…Yezierski et al 30 , stimulating somatosensory cortex and Andy 3 , stimulating MT, were also able to accomplish pain relief.…”