Neuromodulation of Lidocaine and Capsaicin Cream Effects on Pain Experience

Not Applicable

Completed

Conditions: Pain

Interventions: Device: transcranial direct current stimulation (tDCS)
Other: Lidocaine cream
Other: Capsaicin cream
Other: Control cream

Registration Number: NCT03102710

Lead Sponsor: Massachusetts General Hospital

Brief Summary: The aim of this study is to use a brain stimulation tool called transcranial direct current stimulation (tDCS) to investigate the analgesic (reducing sensitivity to pain) effects of lidocaine cream and the hyperalgesic (increasing sensitivity to pain) effects of capsaicin cream using a neutral cream as a control. tDCS stimulation has been shown to temporarily influence the way the stimulated part of the brain functions. With this method, the involvement of specific parts of the brain can be investigated in the working of the brain as a whole.

Detailed Description: Not available

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 103

Inclusion Criteria

Right handed healthy male and female adults aged 21-50
No contraindications to fMRI scanning
At least a 10th grade English-reading level; English can be a second language provided that the patients feel they understand all the questions used in the assessment measures.

Exclusion Criteria

Current or past history of major medical, neurological, or psychiatric illness
Claustrophobia
History of head trauma
Instability of responses to experimental pain
Non-fluent speaker of English
Presence of any contraindications to fMRI scanning. For example: cardiac pacemaker, metal implants, fear of closed spaces, pregnancy
History of alcohol/substance abuse

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
tDCS Enhancement	Capsaicin cream	In this group, the transcranial direct current stimulation (tDCS) stimulates the areas of the brain being examined in this study to increase their activity.
tDCS Enhancement	Control cream	In this group, the transcranial direct current stimulation (tDCS) stimulates the areas of the brain being examined in this study to increase their activity.
tDCS Inhibition	Capsaicin cream	In this group, the transcranial direct current stimulation (tDCS) inhibits the areas of the brain being examined in this study to decrease their activity.
tDCS Inhibition	Control cream	In this group, the transcranial direct current stimulation (tDCS) inhibits the areas of the brain being examined in this study to decrease their activity.
tDCS Enhancement	Lidocaine cream	In this group, the transcranial direct current stimulation (tDCS) stimulates the areas of the brain being examined in this study to increase their activity.
Sham tDCS	Capsaicin cream	Sham transcranial direct current stimulation (tDCS) does not provide real stimulation though you will not know this until your debriefing at the end of the study. Sham will be used to determine if the results of this study are due to the tDCS or other reasons.
tDCS Inhibition	transcranial direct current stimulation (tDCS)	In this group, the transcranial direct current stimulation (tDCS) inhibits the areas of the brain being examined in this study to decrease their activity.
Sham tDCS	Lidocaine cream	Sham transcranial direct current stimulation (tDCS) does not provide real stimulation though you will not know this until your debriefing at the end of the study. Sham will be used to determine if the results of this study are due to the tDCS or other reasons.
tDCS Enhancement	transcranial direct current stimulation (tDCS)	In this group, the transcranial direct current stimulation (tDCS) stimulates the areas of the brain being examined in this study to increase their activity.
tDCS Inhibition	Lidocaine cream	In this group, the transcranial direct current stimulation (tDCS) inhibits the areas of the brain being examined in this study to decrease their activity.
Sham tDCS	transcranial direct current stimulation (tDCS)	Sham transcranial direct current stimulation (tDCS) does not provide real stimulation though you will not know this until your debriefing at the end of the study. Sham will be used to determine if the results of this study are due to the tDCS or other reasons.
Sham tDCS	Control cream	Sham transcranial direct current stimulation (tDCS) does not provide real stimulation though you will not know this until your debriefing at the end of the study. Sham will be used to determine if the results of this study are due to the tDCS or other reasons.

Primary Outcome Measures

Name	Time	Method
fMRI Resting States Functional Connectivity Changes During Pain Stimulation	up to 2 weeks	We measured changes in blood oxygen level-dependent (BOLD) activity in the brain during pain stimulation. In the outcome measure data table, "placebo contrast" indicates lidocaine - neutral and "nocebo contrast" indicates capsaicin - neutral.
Comparison of Functional Connectivity Changes of the DLPFC Before and After tDCS Stimulation	up to 2 weeks	We investigated the effects of cathodal (inhibition) and anodal (enhancement) tDCS on rDLPFC functional connectivity (FC) with the supplementary motor area (SMA) and anterior insula. Higher Fisher Z-scores represent greater resting-state functional connectivity.

Secondary Outcome Measures

Name	Time	Method
Gracely Sensory Scale Pain Rating Changes in Response to Lidocaine and Capsaicin Creams and tDCS	up to 2 weeks	The Gracely Sensory Scale allows participants to rate the intensity of heat pain stimuli on a scale from 0 to 20, with 0 indicating no pain sensation and 20 indicating extremely intense pain. The outcome measure data table shows mean pain ratings for the lidocaine, capsaicin, and neutral creams after enhancement, inhibition, or sham tDCS stimulation.