This study looks at the effect of combined breathing-controlled electrical stimulation (BreEStim) and transcranial direct current stimulation (tDCS) on neuropathic pain after spinal cord injury, amputation, or brain injury. The hypothesis is that a single session of combined BreEStim and tDCS will produce an additive analgesic effect. This record covers the study in a population of healthy volunteers. Note that this study will also enroll spinal cord injury patients, brain injury patients, and amputation patients and that this study as applied to these other populations will be covered in separate ClinicalTrials.gov records.

Inclusion Criteria:

• between 18 and 75 years
• male and female subjects
• healthy subjects (i.e., no recent injuries or pain)

Exclusion Criteria:

• recent injuries or pain
• have a pacemaker, or other metal and/or implanted devices
• have amputation in their arm(s)
• have spinal cord injury (SCI) involving impairment of arms
• have cognitive impairment from brain injury or are not able to follow commands, or to give consent
• have asthma or other pulmonary disease
• are not medically stable
• have preexisting psychiatric disorders
• alcohol or drug abuse
• have a history of seizures/Epilepsy, or taking benzodiazepines, anticonvulsants, and antidepressants.
• Mini-mental state examination (MMSE), a brief 30-point questionnaire test that is commonly used in the literature, will be used to screen for cognitive impairment. A brain injury patient with a score of 24 or lower on MMSE will be excluded.

1 hour after treatment

Study stopped early, and small numbers of subjects analyzed.