Gary W. Donaldson

Phasic pupil dilation response to noxious stimulation in normal volunteers: Relationship to brain evoked potentials and pain report

Pupillary response to noxious stimulation was investigated in men (n = 11) and women (n = 9). Subjects experienced repeated trials of noxious electrical fingertip stimulation at four intensities, ranging from faint to barely tolerable pain. Measures included pupil dilation response (PDR), pain report (PR), and brain evoked potentials (EPs). The PDR began at 0.33 s and peaked at 1.25 s after the stimulus. Multivariate mixed-effects analyses revealed that (a) the PDR increased significantly in peak amplitude as stimulus intensity increased, (b) EP peaks at 150 and 250 ms differed significantly in both amplitude and latency across stimulus intensity, and (c) PR increased significantly with increasing stimulus intensity. Men demonstrated a significantly greater EP peak amplitude and peak latency at 150 ms than did women. With sex and stimulus intensity effects partialled out, the EP peak latency at 150 ms significantly predicted PR, and EP peak amplitude at 150 ms significantly predicted the PDR peak amplitude.

Postoperative pain trajectories in cardiac surgery patients.

Poorly controlled postoperative pain is a longstanding and costly problem in medicine. The purposes of this study were to characterize the acute pain trajectories over the first four postoperative days in 83 cardiac surgery patients with a mixed effects model of linear growth to determine whether statistically significant individual differences exist in these pain trajectories, and to compare the quality of measurement by trajectory with conventional pain measurement practices. The data conformed to a linear model that provided slope (rate of change) as a basis for comparing patients. Slopes varied significantly across patients, indicating that the direction and rate of change in pain during the first four days of recovery from surgery differed systematically across individuals. Of the 83 patients, 24 had decreasing pain after surgery, 24 had increasing pain, and the remaining 35 had approximately constant levels of pain over the four postoperative days.

Effects of music engagement on responses to painful stimulation.

Objectives:We propose a theoretical framework for the behavioral modulation of pain based on constructivism, positing that task engagement, such as listening for errors in a musical passage, can establish a construction of reality that effectively replaces pain as a competing construction. Graded engagement produces graded reductions in pain as indicated by reduced psychophysiological arousal and subjective pain report. Methods:Fifty-three healthy volunteers having normal hearing participated in 4 music listening conditions consisting of passive listening (no task) or performing an error detection task varying in signal complexity and task difficulty. During all conditions, participants received normally painful fingertip shocks varying in intensity while stimulus-evoked potentials (SEP), pupil dilation responses (PDR), and retrospective pain reports were obtained. Results:SEP and PDR increased with increasing stimulus intensity. Task performance decreased with increasing task difficulty. Mixed model analyses, adjusted for habituation/sensitization and repeated measures within person, revealed significant quadratic trends for SEP and pain report (Pchange<0.001) with large reductions from no task to easy task and smaller graded reductions corresponding to increasing task difficulty/complexity. PDR decreased linearly (Pchange<0.001) with graded task condition. We infer that these graded reductions in indicators of central and peripheral arousal and in reported pain correspond to graded increases in engagement in the music listening task. Discussion:Engaging activities may prevent pain by creating competing constructions of reality that draw on the same processing resources as pain. Better understanding of these processes will advance the development of more effective pain modulation through improved manipulation of engagement strategies.

Distress, Dependency, and Threat in Newly Diagnosed Cancer and Heart Disease Patients

The effects of life-threatening illness on 56 lung cancer and 65 heart attack patients at one and two months postdiagnosis were assessed with objective self-report inventories measuring symptom distress, social dependency, concerns, mood, personality, and evaluation of problem management. Lung cancer patients had more symptom distress and concerns, and evaluated themselves more harshly, than heart attack patients. Although symptom distress remained unchanged, both kinds of patients reported significant improvement in mood and concerns by the second month postdiagnosis; this improvement was interpreted as a result of assimilating the life-threatening aspects of these diseases. Structural equation models of individual differences suggested that, even though the two groups were characterized by mean differences, the causal processes within the two groups were similar, with symptom distress the most pervasive and powerful influence. The importance of conducting both individual differences and group differences analyses was stressed.

Personality, Anxiety, and Individual Variation in Psychophysiological Habituation and Sensitization to Painful Stimuli

Habituation and sensitization are two fundamental consequences in response to repeated painful stimulation. However, individual differences as to who systematically habituate versus sensitize are currently not well understood. Investigating changes in response modulation (habituation and sensitization) in laboratory subjects undergoing pain testing, we evaluated the hypotheses: 1) significant individual differences exist in patterns of habituation and sensitization, and 2) variations in response modulation are systematically associated with subjects’ characteristic personality styles. We explored personality and state predictors of individual differences in response modulation consisting of habituation and sensitization in pain-free, healthy subjects. We recruited 81 healthy subjects who underwent 36 trials of painful stimulations to their fingertips. Subjective pain reports and psychophysiological responses - evoked potential (EP) and skin conductance response (SCR) - served as measurement indicators for habituation and sensitization, and to evaluate how these different measures manifested in the group averages as well as in correlations across individuals. Results showed that although subjective pain report tended to indicate sensitization on average, both EP and SCR showed habituation. However, further analyses revealed that there was a positive convergence among the three channels across different subjects, suggesting that individuals tend to have consistent response styles in responding to repeated pain stimulations. Our analyses allowed us to make inferences about the relative proportions of individuals in the population who systematically habituate versus sensitize. Variations in the habituation-sensitization continuum are highly robust and systematic, and preexisting individual characteristics (personality and current psychological states such as state anxiety) in part accounted for these patterns.

Activity rhythms and clinical correlates in fibromyalgia

Abstract The primary aim of this study was to evaluate activity rhythms in fibromyalgia syndrome (FMS) and their association with FMS-related symptoms. We hypothesized that stronger and more consistent activity rhythms would be associated with reduced symptom severity and presentation in FMS. Two hundred ninety-two patients with FMS (mean age = 45.1 ± 11.1; 272 women) provided a 7-day actigraphy recording and responses to questionnaires addressing degree of pain, fatigue, mood, and physical impairment. Using a simple cosine model, we extracted Amplitude (activity range), Phi (time at maximum), Mesor (mean activity), and their variabilities (across days) from each participants actigraphy. The clinical and actigraphic measures were operationally independent. There was a significant canonical relationship between activity rhythm parameters and clinical FMS measures (r = 0.376, R2 = 0.14, P < 0.001). The set of Mesor, Amplitude, and Phi activity parameters remained associated with clinical measures when controlled statistically for both demographics and activity variability (P < 0.001). Each activity parameter provided unique discrimination of the clinical set by multivariate test (P = 0.003, 0.018, and 0.007 for Amplitude, Phi, and Mesor, respectively). These results revealed that better pain, fatigue, mood, physical impairment, and sleep outcomes were associated with higher activity range and more rhythmicity (Amplitude), increased mean activity (Mesor), and with earlier timing of peak activity (Phi). Exploratory analyses revealed significantly worse sleep for individuals with low Amplitude and more delayed Phi.