Journal of Neurophysiology, Vol 61, Issue 1 106-115, Copyright © 1989 by APS
Patterns of spontaneous discharge in primate spinothalamic neurons
D. J. Surmeier, C. N. Honda and W. D. Willis
Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77550.
1. The spontaneous discharge of 30 spinothalamic tract (STT) neurons in the
lumbosacral spinal cord of anesthetized monkeys was studied. Interval,
correlation, and spectral analyses were performed. 2. Three patterns of
discharge were found; these were referred to as the SP1, SP2, and SP3
patterns. 3. The SP1 group had moderately regular discharge trains that
were devoid of short-interval spike bursts. 4. The SP2 group had spike
trains dominated by short-interval bursts without evidence of low-frequency
rhythmicity. 5. The SP3 group had spike trains with features of both the
SP1 and SP2 groups. 6. Some correlations were found between the mean
discharge rate and stimulus-response classes previously defined by our
group (25). Correlations were deduced from a parent data set of 221 STT
neurons. Type 1 neurons, which were driven primarily by tactile afferents,
were found to have significantly lower mean rates than other
"within-neuron" groups. On the other hand, type C neurons, which had strong
input from afferents signalling pressure and noxious stimuli, were found to
have significantly higher mean rates than all other "across-neuron"
classes. 7. A weak relationship was found between the pattern of discharge
and the within-neuron stimulus-response classification. Neurons with a
largely tactile coding orientation (types 1 and 2) were most frequently of
the SP1 and SP2 classes, whereas neurons with a more prominent nociceptive
input (types 3 and 4) were most frequently of the SP2 and SP3 classes. No
relationship was apparent between discharge pattern and the across-neuron
classes.
