Objective: The objective of this study is to summarize and analyze the brain signal patterns of empathy for pain caused by facial expressions of pain utilizing activation likelihood estimation, a meta-analysis method.
Data sources: Studies concerning the brain mechanism were searched from the Science Citation Index, Science Direct, PubMed, DeepDyve, Cochrane Library, SinoMed, Wanfang, VIP, China National Knowledge Infrastructure, and other databases, such as SpringerLink, AMA, Science Online, Wiley Online, were collected. A time limitation of up to 13 December 2016 was applied to this study.
Data selection: Studies presenting with all of the following criteria were considered for study inclusion: Use of functional magnetic resonance imaging, neutral and pained facial expression stimuli, involvement of adult healthy human participants over 18 years of age, whose empathy ability showed no difference from the healthy adult, a painless basic state, results presented in Talairach or Montreal Neurological Institute coordinates, multiple studies by the same team as long as they used different raw data.
Outcome measures: Activation likelihood estimation was used to calculate the combined main activated brain regions under the stimulation of pained facial expression.
Results: Eight studies were included, containing 178 subjects. Meta-analysis results suggested that the anterior cingulate cortex (BA32), anterior central gyrus (BA44), fusiform gyrus, and insula (BA13) were activated positively as major brain areas under the stimulation of pained facial expression.
Conclusion: Our study shows that pained facial expression alone, without viewing of painful stimuli, activated brain regions related to pain empathy, further contributing to revealing the brain's mechanisms of pain empathy.
Keywords: GringleALE; activation likelihood estimation; anterior central gyrus; anterior cingulate cortex; brain function imaging; facial expression; functional magnetic resonance imaging; fusiform gyrus; insula; nerve regeneration; neural regeneration; pain empathy.