Journal of neurophysiology
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1. Single-unit electrical activity has been recorded from 42 dorsal horn neurons in the sacral segments of the rat's spinal cord. The sample consisted of 20 multireceptive (class 2) cells with both A- and C-fiber inputs and 22 nocireceptive (class 3) cells. ⋯ The RFs of the class 3 neurons, which were initially smaller than those of the class 2 cells, either did not increase in size or showed very small increases after the pinch stimuli (38.3 +/- 11.95 mm2, mean +/- SE). 6. Some cells in both groups (6/10 class 2 cells and 7/16 class 3 cells) showed a decrease in mechanical threshold as a result of the noxious mechanical stimulus, but none of the class 3 cells' thresholds dropped below 20 mN into the low-threshold range. 7. The results obtained in the halothane-anesthetized and decerebrate-spinal animals were very similar to those seen in the barbiturate-anesthetized experiments, with the exception that in the decerebrate-spinal animals, the RFs of the class 2 cells were initially larger and showed only small increases.(ABSTRACT TRUNCATED AT 400 WORDS)
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Comparative Study
Patterns of intracellular potentials in salamander mitral/tufted cells in response to odor stimulation.
1. Changes in membrane potential and temporal patterns of spikes were analyzed in 30 output cells in the salamander olfactory bulb in response to stimulation with 1-s pulses of the odorants isoamyl acetate, cineole, and camphor. The odor responses were more complex than responses to electrical stimulation of the olfactory nerve or olfactory tracts, with which they were compared. ⋯ However, the range of spike latencies overlapped that of S-type responses to high concentrations. With increasing odor concentration, spike latencies in the E-type responses decreased relative to the onset and peak of the initial hyperpolarization. At high concentrations. spikes were frequently elicited preceding a single period of hyperpolarization and inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)
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1. The magnitude of the sensations produced by small increases in thermal stimuli superimposed on noxious levels of heat stimulation was studied by the use of a simple reaction-time task. Noxious thermal stimuli were presented on the face of three monkeys, the forearm volar surface of three monkeys, and the face of four human subjects. ⋯ A cross-modality matching procedure was used to examine the perceived intensity of pain sensation produced by T2 stimuli in human subjects. The magnitude estimates of these stimuli were dependent on the level of T1, as well as the intensity of T2. Detection speed, plotted as a function of the estimated magnitude of pain, independent of T1 and T2 temperature, was best fit by a logarithmic function.(ABSTRACT TRUNCATED AT 400 WORDS)
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1. We examined the relationship between the activity of medullary dorsal horn nociceptive neurons and the monkeys' ability to detect noxious heat stimuli. In two different detection tasks, the temperature of a contact thermode positioned on the monkey's face increased from 38 degrees C to temperatures between 44 and 48 degrees C (T1). ⋯ There was a significant correlation between detection speed and neuronal discharge for WDR1 and WDR2 neurons. No correlation was observed for NS neurons. 5. The magnitude of neuronal activity on correctly detected and nondetected trials was compared when T1 was 46 degrees C and T2 was 0.2 degree C.(ABSTRACT TRUNCATED AT 400 WORDS)
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1. We examined the activity of thermally sensitive trigeminothalamic neurons and nonprojection neurons in the medullary dorsal horn (trigeminal nucleus caudalis) in three monkeys performing thermal and visual detection tasks. 2. An examination of neuronal stimulus-response functions, obtained during thermal-detection tasks in which noxious heat stimuli were applied to the face, indicated that wide-dynamic-range neurons (WDR, responsive to innocuous mechanical stimuli with greater responses to noxious mechanical stimuli) could be subclassified based on the slope values of linear regression lines. ⋯ These task-related responses were time-locked to specific behavioral events associated with trial initiation and trial continuation. 6. These data provide evidence that a subpopulation of WDR neurons is the dorsal horn cell type most sensitive to small increases in noxious heat in the 45-49 degrees C temperature range and provides the most information about stimulus intensity. The findings support the view that nociceptive neurons have the capacity to precisely encode stimulus features in the noxious range and that WDR neurons are likely to participate in the monkeys' ability to perceive the intensity of such stimuli.