The relationship between fear generalization and pain modulation: an investigation in healthy participants

Background and aimsPain-related fear and its subsequent generalization is key to the development and maintenance of chronic pain disability. Research has shown that pain-related fear acquired through classical conditioning generalizes following a gradient, that is, novel movements that are proprioceptively similar to the original pain-associated movement elicit more fear. Studies suggest that classical conditioning can also modulate pain and conditioned fear seems to mediate this effect. However, it remains uninvestigated whether this is also the case for generalized fear.MethodsIn a voluntary joystick movement paradigm, one movement (conditioned stimulus; CS+) was followed by pain (pain-US), and another was not (CS−). Generalization to five novel movements (generalization stimuli; GSs) with varying levels of similarity to the CSs was tested when paired with an at-pain-threshold intensity stimulus (threshold-USs). We collected self-reported fear and pain, as well as eyeblink startle responses as an additional index of conditioned fear.ResultsResults showed a fear generalization gradient in the ratings, but not in the startle measures. The data did not support the idea that fear generalization mediates spreading of pain.ConclusionsDespite the lack of effects in the current study, this is a promising novel approach to investigate pain modulation in the context of chronic pain.ImplicationsThis study replicates the finding that pain-related fear spreads selectively towards movements that are proprioceptively more similar to the original pain-eliciting movement. Although results did not support the idea that such generalized fear mediates spreading of pain, the study provides a promising approach to investigate pain modulation by pain-associated movements.

Preprint: Empirically-based comparisons of the reliability and validity of common quantification approaches for eyeblink startle potentiation in humans

Startle potentiation is a well validated translational measure of negative affect. Startle potentiation is widely used in clinical and affective science and there are multiple approaches for its quantification. The three most commonly used approaches quantify startle potentiation as the increase in startle response from a neutral to threat condition based on 1) raw potentiation, 2) standardized potentiation or 3) percent-change potentiation. These three quantification approaches may yield qualitatively different conclusions about effects of independent variables on affect when within or between group differences exist for startle response in the neutralcondition. Accordingly, we directly compared these quantification approaches in a shock-threat task using four independent variables known to influence startle response in the no-threat condition: probe intensity, time (i.e., habituation), alcohol administration, and individual differences in general startle reactivity measured at baseline. We confirmed the expected effects of time, alcohol, and general startle reactivity on affect using self-reported fear/anxiety as a criterion. The percent-change approach displayed apparent artifact across all four independent variables, which raises substantial concerns about its validity. Both raw and standardized potentiation approaches were stable across probe intensity and time, which supports their validity. However, only raw potentiation displayed effects that were consistentwith a priori specifications and/or the self-report criterion for the effects of alcohol and general startle reactivity. Supplemental analyses of reliability and validity for each approach provided additional evidence in support of raw potentiation.

An Association between Nature Exposure and Physiological Measures of Emotion and Cognition

Nature environments have significant benefits for human psychological functioning, in both the cognitive and emotional domains. These positive effects have been found primarily with questionnaires, performance measures, and transient physiological measures. This study explores the long-term relationships between degree of nature exposure and physiological states. With a publically available dataset, multiple hierarchical regressions were conducted testing the relationship between reported nature exposure and two physiological measures of cognition and emotion, including alpha band EEG asymmetry and degree of eyeblink startle reflex (EBR). A significant relationship was found with nature exposure and these measures, suggesting that nature has enduring positive effects for human functioning via measured physiology.

Prepulse Inhibition in HIV-Associated Neurocognitive Disorders

Sensorimotor inhibition, or the ability to filter out excessive or irrelevant information, theoretically supports a variety of higher-level cognitive functions. Impaired inhibition may be associated with increased impulsive and risky behavior in everyday life. Individuals infected with HIV frequently show impairment on tests of neurocognitive function, but sensorimotor inhibition in this population has not been studied and may be a contributor to the profile of HIV-associated neurocognitive disorders (HAND). Thirty-seven HIV-infected individuals (15 with HAND) and 48 non-infected comparison subjects were assessed for prepulse inhibition (PPI), an eyeblink startle paradigm measuring sensorimotor gating. Although HIV status alone was not associated with PPI deficits, HIV-positive participants meeting criteria for HAND showed impaired PPI compared to cognitively intact HIV-positive subjects. In HIV-positive subjects, PPI was correlated with working memory but was not associated with antiretroviral therapy or illness factors. In conclusion, sensorimotor disinhibition in HIV accompanies deficits in higher-order cognitive functions, although the causal direction of this relationship requires investigation. Subsequent research on the role of sensorimotor gating on decision-making and risk behaviors in HIV may be indicated. (JINS, 2013, 19, 1–9)