Trial Outcomes & Findings for N-of-few Study of Pain Perception (NCT NCT04664400)

Results Overview

Each session of the experiment includes pain tasks, in which multiple thermal stimuli are delivered. Following each thermal stimulus, participants are asked to rate how painful it was, on a semi-circular computerized scale. Ratings are based on the angle (0-180), with higher angle representing higher pain ratings. In the symbolic learning procedure, cues are conditioned to different temperatures based on pictures of thermometers (instead of actual thermal stimuli as in the conditioning procedure). For the cues that were learned via symbolic learning, the investigators will compare the average rating of pain for stimuli that are preceded by high cues minus the average rating of pain for stimuli that are preceded by low cues (each averaged across sessions), within participant.

Recruitment status

COMPLETED

Study phase

NA

Target enrollment

10 participants

Primary outcome timeframe

Measured repeatedly during pain tasks, in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability), immediately after thermal stimuli. Averaged across sessions and compared across conditions.

Results posted on

2023-04-18

Participant Flow

Participant milestones

Participant milestones
Measure	N-of-few Study of Pain Symbolic conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers) Conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli). Instructions: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions. Counterfactual: Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.
Overall Study STARTED	10
Overall Study COMPLETED	8
Overall Study NOT COMPLETED	2

Reasons for withdrawal

Reasons for withdrawal
Measure	N-of-few Study of Pain Symbolic conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers) Conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli). Instructions: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions. Counterfactual: Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.
Overall Study Withdrawal by Subject	2

Baseline Characteristics

N-of-few Study of Pain Perception

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Main Arm n=8 Participants Symbolic conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers) Conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli). Instructions: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions. Counterfactual: Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.
Age, Continuous	20.875 years STANDARD_DEVIATION 1.126 • n=5 Participants
Sex: Female, Male Female	6 Participants n=5 Participants
Sex: Female, Male Male	2 Participants n=5 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	2 Participants n=5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	6 Participants n=5 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=5 Participants
Race (NIH/OMB) Asian	2 Participants n=5 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=5 Participants
Race (NIH/OMB) Black or African American	0 Participants n=5 Participants
Race (NIH/OMB) White	5 Participants n=5 Participants
Race (NIH/OMB) More than one race	0 Participants n=5 Participants
Race (NIH/OMB) Unknown or Not Reported	1 Participants n=5 Participants
Region of Enrollment United States	8 participants n=5 Participants

PRIMARY outcome

Timeframe: Measured repeatedly during pain tasks, in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability), immediately after thermal stimuli. Averaged across sessions and compared across conditions.

Each session of the experiment includes pain tasks, in which multiple thermal stimuli are delivered. Following each thermal stimulus, participants are asked to rate how painful it was, on a semi-circular computerized scale. Ratings are based on the angle (0-180), with higher angle representing higher pain ratings. In the symbolic learning procedure, cues are conditioned to different temperatures based on pictures of thermometers (instead of actual thermal stimuli as in the conditioning procedure). For the cues that were learned via symbolic learning, the investigators will compare the average rating of pain for stimuli that are preceded by high cues minus the average rating of pain for stimuli that are preceded by low cues (each averaged across sessions), within participant.

Outcome measures

Outcome measures
Measure	N-of-few Study of Pain n=8 Participants Symbolic conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers) Conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli). Instructions: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions. Counterfactual: Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.
Within Participant Subjective Ratings of Acute Thermal Pain Following High Compared to Low Cues (Learned Via Symbolic Learning)	7.32 score on a scale Standard Deviation 10.41

PRIMARY outcome

Timeframe: Measured repeatedly during pain tasks, in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability), immediately after thermal stimuli. Averaged across sessions and compared across conditions.

Each session of the experiment includes pain tasks, in which multiple thermal stimuli are delivered. Following each thermal stimulus, participants are asked to rate how painful it was, on a semi-circular computerized scale. Ratings are based on the angle (0-180), with higher angle representing higher pain ratings. In the conditioning procedure, cues are conditioned to different temperatures by delivering thermal stimuli with different temperatures after cues are presented (higher temperature following high cues and lower temperature following low cues). For the cues that were learned via conditioning, the investigators will compare the average rating of pain for stimuli that are preceded by high cues minus the average rating of pain for stimuli that are preceded by low cues (each averaged across sessions), within participant.

Outcome measures

Outcome measures
Measure	N-of-few Study of Pain n=8 Participants Symbolic conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers) Conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli). Instructions: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions. Counterfactual: Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.
Within Participant Subjective Ratings of Acute Thermal Pain Following High Compared to Low Cues (Learned Via Conditioning)	13.21 score on a scale Standard Deviation 17.72

PRIMARY outcome

Timeframe: Measured repeatedly during pain tasks, in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability), immediately after thermal stimuli. Averaged across sessions and compared across conditions.

Each session of the experiment includes pain tasks, in which multiple thermal stimuli are delivered. Following each thermal stimulus, participants are asked to rate how painful it was, on a semi-circular computerized scale. Ratings are based on the angle (0-180), with higher angle representing higher pain ratings. In the instructions only condition, cues are learned via verbal suggestion. For the cues that were learned via instructions only, the investigators will compare the average rating of pain for stimuli that are preceded by high cues minus the average rating of pain for stimuli that are preceded by low cues (each averaged across sessions), within participant.

Outcome measures

Outcome measures
Measure	N-of-few Study of Pain n=8 Participants Symbolic conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers) Conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli). Instructions: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions. Counterfactual: Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.
Within Participant Subjective Ratings of Acute Thermal Pain Following High Compared to Low Cues (Learned Via Instructions Only)	13.76 score on a scale Standard Deviation 13.51

PRIMARY outcome

Timeframe: Measured repeatedly during pain tasks, in each of the last 4 sessions of the experiment, immediately after thermal stimuli. Averaged across sessions and compared across conditions.

In the counterfactual task, participants are presented with two alternatives (either two pain levels, or one pain level and either losing or gaining a certain amount of money). In these pairs of alternatives, the medium level pain is sometimes the better option (i.e., when the alternative is losing money or a more intense pain stimulus) and sometimes the worse option (i.e., when the other alternative is gaining money or a less intense pain stimulus). One of the two options is chosen by the computer (participants have no control on this choice). The investigators will compare the pain ratings (scale 0-180) within participant for the same level pain stimulus (medium intensity) when it is the worse vs. the better option.

Outcome measures

Outcome measures
Measure	N-of-few Study of Pain n=8 Participants Symbolic conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers) Conditioning: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli). Instructions: Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions. Counterfactual: Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.
Within Participant Subjective Ratings of Acute Thermal Pain, When it is the Worse vs. the Better Alternative	-2.06 score on a scale Standard Deviation 5.57

OTHER_PRE_SPECIFIED outcome

Timeframe: Measured continuously during pain stimuli in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability). Averaged and compared across conditions.

Other adverse events

Adverse event data not reported

Additional Information

Tor D Wager, PhD

Dartmouth College

Phone: (603)-646-2196

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place