The conditioned expectation of pain is an important aspect of pain-related disability produced by environments and stimuli associated with a painful injury on the job, although the neuroscience of this expectation is unclear. We will develop and use novel objective methods for measurement of expectation and threat related attention. The results of this study may lead to testable hypotheses regarding the psychological basis of the fear of pain, threat and task related attention. We will also use these results, and development of novel autonomic and ratings metrics for state and trait anxiety as well as threat and task related attention which could be used as an instrumented test for diagnosis and management of PTSD and anxiety disorders. .
The conditioned expectation or fear of pain often results in disability produced by stimuli related to a painful injury on the job, although there are questions about attentional and anxiety related expectation. Conditioned expectation in humans can be produced by a protocol that consists of a train of two visual conditioning stimuli, one of which is paired (CS+) with a painful laser pulse unconditioned stimulus (US), while the other is not. This protocol will be used to study the expectation of pain in this study, and its relationship to task and threat related attention measured by eye position and to anxiety, task directed sustained attention, and scalp EEG metrics. These results may also be used in an instrumented test for the diagnosis and management of PTSD and anxiety disorders. EEG studies may clarify the relationship of unpleasantness (valence) and the ability of stimuli to command attention (salience) of the conditioned and unconditioned stimuli which which are significant but under studied aspects of the fear of the pain. Studies of scalp EEG activation and functional connectivity will be used to estimate global properties of the forebrain networks involved in the fear of pain, as well as the valence and the salience) of the conditioned and unconditioned stimuli. Activations are measured by the proportion of electrodes over a quadrant or lobe of the scalp a significant ratio of electrical power following an event over baseline (event related spectral perturbation, ERSP). Functional connectivity will be measured by causal interactions following an event over baseline. The approach of this protocol is that causal interactions are based upon causal influences by an approach based upon the concept of linear predictability. Briefly, a signal Y is said to exert an influence upon signal X when the predication error of the X is reduced by adding the past information of Y (causal interaction). The signals from any two quadrants or lobes will be analyzed by event related causality to determine the magnitude and direction of causal interactions between the two to determine fear and pain related directed interactions related to aversive conditioning. Our Preliminary Data shows EEG activations in global distributed forebrain networks for the expectation of pain are consistent with the evidence of studies of anatomic projections and functional MRI (fMRI) signals. These models including our Preliminary Data from intracranial recordings identify structures in the medial temporal lobe (amygdala and hippocampus) which are involved in expectation of pain, while EEG suggests global activations related to valence and salience of conditioned and unconditioned stimuli. The premise of this study is that novel autonomic and eye position metrics will measure state and trait anxiety as well as threat and task related attention to parse out the experience and anticipation of pain.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
32
After fear conditioning the cue induces autonomic responses like skin conductance and cognitive ratings like expectancy of the unconditioned stimulus after cueing or conditioning. Activity across blocks in the conditioning stage shows that the skin conductance can be described by levels, and slopes which might be related to state anxiety and trait anxiety (Spielberger trait and state anxiety inventory or questionnaire). These skin conductance measures may be concrete metrics for psychological processes in healthy subjects. We will carry out a partial correlation analysis of levels, state anxiety and trait anxiety, and then a similar analysis of slopes, state anxiety and trait anxiety. These results may show that concrete skin conductance levels and slopes are related to metrics of subjective self report measures of state and trait anxiety.
Hopkins Epilepsy Monitoring Unit, Zayhed 12.
Baltimore, Maryland, United States
Skin Conductance Response
Concrete metric is skin conductance response to painful laser pulse stimulus measured in microSiemens. Higher values mean more emotional arousal or stress. All participants experienced two types of conditioned stimuli, one stimulus signaled danger and the other safety. Only during the danger stimulus would the participant receive a laser pulse.
Time frame: 5 seconds post conditioned stimulus
State Anxiety as Assessed by the Spielberger State-Trait Anxiety Inventory
The Spielberger State-Trait Anxiety Inventory (STAI) is a 40-item self-report questionnaire with 20 items designed to assess State anxiety (temporary feelings of anxiety). The State anxiety score range is between 20 and 80 with higher scores representing higher anxiety. State anxiety was measured and is reported.
Time frame: Baseline, post conditioning up to 6 minutes
Experimental Pain as Assessed by a Pain Rating Scale
Pain Rating for Unpleasantness on a scale of 0 - 10 where 10 is the worst imaginable. All participants experienced two types of conditioned stimuli, one stimulus signaled danger and the other safety. Only during the danger stimulus would the participant receive a laser pulse.
Time frame: Post conditioning approximately 6 minutes
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