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Biomedical subjects

Donald D Price

Publications and source records attributed to Donald D Price.

78 records · Page 5Linked to original sources
PubMed1980

A psychophysical analysis of experimential factors that selectively influence the affective dimension of pain.

A psychophysical analysis was made of experiential factors that influence the affective but not the sensory-discriminative dimension of pain. Seven subjects made cross-modality matching responses to several dimensions of their experience. Before each stimulus, they matched line lengths to their experienced desire to avoid pain (significance) and to their perceived likelihood of avoiding it (expectation). After each stimulus, they matched line lengths to perceived sensation intensity (in some sessions) or to felt magnitudes of positive or negative feeling (in other sessions). Non-noxious (35, 42 degrees C) and noxious (45--51 degrees C) skin temperature stimuli were randomly interspersed during each experimental session. Changes in expectation were induced by preceding one-half of the noxious stimuli with a warning signal. The average responses of these subjects indicated that 45--51 degrees C noxious temperatures were felt as less unpleasant when preceded by a warning signal. In contrast, sensation magnitudes evoked by these same skin temperatures were unaffected by the warning signal. Thus, only the magnitudes of unpleasant responses are lowered by decreasing ones' expectation of avoiding pain. Analysis of individual responses revealed two distinct patterns of response changes following presentation of the warning signal. Four subjects retained the same general goal of avoiding pain and reduced their expectation of avoiding it. Their affective responses were less unpleasant during the warning signal. The remaining three subjects primarily altered their goals and not their expectations on signaled trials. Their affective responses were not modified by the signal. Subjects were instructed to arrive at their affective responses in two ways. In one session, they compared the outcome of each stmulation with what they wanted to happen (affect-result responses). In the other session, they simply focused on the pleasantness or unpleasantness of each sensation as it was experienced (affect-process responses). All subjects' affect-result responses were more positive (or less unpleasant) than affect-process responses. All of these results underscore the critical influence of expectations and the manner in which one evaluates sensations on affective responses to noxious stimulation.

Adult↗
PubMed1977

Peripheral suppression of first pain and central summation of second pain evoked by noxious heat pulses.

Psychophysical experiments were carried out on 6 huma subjects to determine how first and second pain are influenced by peripheral receptor mechanisms and by central nervous system inhibitory and facilitatory mechanisms. For these experiments, brief natural painful stimuli delivered to the hand were a train of 4-8 constant waveform heat pulses generated by a contact thermode (peak temp. = 51-5% C). The magnitude of first and second pain sensations was estimated using cross-modality matching procedures and reaction times were determined. The latter confirmed the relationship between first and second pain and impulse conduction in Adelta and C noxious heat afferents, respectively. The intensity of first pain decreased with each successive heat pulse when the interpulse interval was 80 sec or less. This decrease was most likely the result of heat induced suppression of Adelta heat nociceptors since it did not occur if the probe location changed between successive heat pulses. In contrast, second pain increased in intensity with each successive heat pulse if the interval was 3 sec or less. This summation was most likely due to central nervous system summation mechanisms since it also occurred after blockage of first pain by ulnar nerve compression and when the location of the thermode changed between heat pulses. These observations and their interpretations are supported by our recording of responses of singlt Adelta heat nociceptive afferents, C polymodal nociceptive afferents, and "warm" afferents of rhsus monkeys to similar trains of noxious heat pulses. Their responses to these heat pulses show a progressive suppression. Furthermore, previous studies have shown that wide dynamic range dorsal horn neurons show summated responses to repeated volleys in C fibers (greater than 1/3 sec). These spinal cord summation mechanisms could account for the summation of second pain.

Adult↗
PubMed1975

Neurophysiological characterization of the anterolateral spinal cord neurons contributing to pain perception in man.

These studies have examined threshold, frequency, and refractory period characteristics of a neural population in the anterolateral quandrant (ALQ) of the spinal cord of man, stimulation of which produces pain. Subjects were 18 conscious humans undergoing percutaneous anterolateral cordotomy for relief of intractable pain. Pain could be produced by ALQ stimulation in all subjects. Pain thresholds ranged from 120 to 1000 muA (at 50 pulses/sec; 0.2 msec pulses), but the majority of thresholds were below 300 muA. A linear relationship was found between stimulation frequency and percentage of subjects reporting pain. This relationship ranged from 5 to 25 pulses/sec with 100% reporting pain at 25/sec and 0% at 5/sec. In 2 of 3 subjects, increases in stimulation frequency up to 500/sec did not produce pain when stimulation intensity was below threshold at 50/sec. The neuronal refractory period for pain in these subjects ranged between 1.0 and 2.0 msec, but the majority of relative refractory periods fell between 1.0 and 1.5 msec. The threshold, frequency, and refractory period data obtained in this study are similar to those found for wide dynamic range cells in the ventral half of the dorsal horn in the monkey and suggest that activation of these cells is a sufficient condition to produce pain in man.

Animals↗
PubMed1975

Neurophysiological characterization of the anterolateral quadrant neurons subserving pain in M. mulatta.

An electrophysiological analysis has been made of 82 L7 dorsal horn neurons antidromically activated from the contralateral C1 anterolateral quadrant (ALQ) of unanesthetized rhesus monkeys (bilateral carotid ligation). This analysis was made to compare refractory periods and antidromic activation thresholds with these same parameters of ALQ stimulation required to produce pain in conscious humans. Refractory periods of laminae IV-VI cells that were optimally but not exclusively responsive to noxious skin stimulation ranged from 0.8 to 2.8 msec (m = 1.5) and were briefer than those of lamina I cells. The latter ranged from 1.1 to 10 msec (m = 4.7 msec). Electrical thresholds of laminae IV-VI cells were, in general, much lower than those of lamina I cells. Unlike lamina I cells, refractory periods and electrical thresholds of laminae IV-VI nociceptive neurons closely parallel those of ALQ-evoked pain in man. However, both lamina I and laminae IV-VI neurons usually responded to nociceptive skin temperatures (greater than 43 degrees C). This analysis indicates that pain may be signaled by the combined output of dorsal horn laminae I and IV-VI but that activation of only laminae IV-VI wide dynamic range neurons is sufficient to produce pain.

Action Potentials↗