Do the Neural Correlates of Acupuncture and Placebo Effects Differ

Do the Neural Correlates of Acupuncture and Placebo Effects Differ
Published online 2007 January 30
Rupali P. Dhond,1,2 Norman Kettner,2 and Vitaly Napadow1,2
Pain
PubMed Central

1 MGH/MIT/HMS Martinos Center for Biomedical Imaging, Charlestown, MA 02129

2 Logan College of Chiropractic, Department of Radiology, Chesterfield, MO 63017

Address Correspondence To: Polly Dhond, Ph.D. 149 13th St. Rm.2301, Charlestown, MA 02129, 617-726-7422 (fax), Email: polly@nmr.mgh.harvard.edu

Abstract

The neurophysiological basis of therapeutic acupuncture is not well understood but is likely to consist of both specific and non-specific (e.g. placebo) effects. Data from animal studies suggest that endogenous anti-nociceptive networks may play a large role in therapeutic acupuncture. These networks have also been demonstrated to support placebo analgesia making differentiation between acupuncture specific and non-specific networks challenging. However, modern neuroimaging techniques such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), electroencephalography (EEG) and magnetoencephalography (MEG) provide a means to safely monitor brain activity in humans and may be used to help map the neural correlates of acupuncture. Recent neuroimaging studies have explored brain activity during acupuncture stimulation and/or the analgesic effects of acupuncture on pain stimulus processing. Although controversy regarding appropriate control methodology (e.g. sham acupuncture) continues, data suggest that modulation of certain limbic brain networks may differentiate between specific and placebo components of acupuncture.

Keywords: acupuncture, placebo, pain, alternative medicine, fMRI, PET, MEG, EEG, neuroimaging, amygdala, hypothalamus, somatosensory, limbic, cingulate, brainstem, frontal cortex, complementary, opioidergic, monaminergic

Introduction

Acupuncture is an ancient Chinese healing modality with putative therapeutic effects for clinical pain management. However, it is often dismissed by mainstream allopathic medicine due to a paucity of data demonstrating its neurophysiological differentiation from placebo. Functional neuroimaging provides a means to determine which brain networks support acupuncture as well as map the differences between its specific and non-specific neural correlates. It is important to remember that although placebo effects can occur with all forms of medical treatment their neurophysiological basis may differ with the type of treatment being given (Colloca and Benedetti 2005). In general, placebo effects are believed to arise from unconscious conditioning (Voudouris et al. 1990; Wickramasekera 1999), changes in (verbal) expectancy (Montgomery and Kirsch 1997), and/or differences in practitioner suggestion and patient suggestibility (De Pascalis et al. 2002; Wickramasekera 1999). However, these effects likely overlap and there is strong evidence that expectancy is the major contributor to increasing treatment efficacy (Montgomery and Kirsch 1997). Thus, acupuncture specific brain activity must be differentiated from non-specific activity supporting subject expectations for treatment.

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