Consecutive Acupuncture Stimulations Lead to Significantly Decreased Neural Responses

Abstract

Objective: Functional magnetic resonance imaging (fMRI), in combination with block design paradigms with consecutive acupuncture stimulations, has often been used to investigate the neural responses to acupuncture. In this study, we investigated whether previous acupuncture stimulations can affect brain activations of later acupuncture stimulations. Design: All subjects were measured twice in the same scanning session and a block design was used. Setting: The study was conducted at Kyung Hee University, Seoul, Republic of Korea. Subjects: Fifteen (15) healthy right-handed male volunteers participated in the study. Intervention: The subjects received two acupuncture stimulations on BL62 (Shenmai) on the right foot with a time interval of 5 minutes. In addition, sham stimulations were tested with the same paradigm. Outcome measures: One-sample t tests were conducted in order to map the brain activations induced by the acupuncture and sham stimulations. Moreover, paired-sample t tests were conducted to investigate the signal changes between the first and second acupuncture stimulation. Results: During the first acupuncture stimulation, in the left hemisphere, significant foci of activation were found in the hypothalamus, thalamus, claustrum, cerebellum, inferior frontal gyrus, and the superior temporal gyrus. In the right hemisphere, a significant focus of activation was found in the middle frontal gyrus. In addition, in both hemispheres, a significant focus of activation was found in the inferior parietal lobule. Interestingly, however, during the second acupuncture stimulation, the only areas that were also significantly activated were the cerebellum in the left hemisphere and the inferior parietal lobule in the right hemisphere. Conclusions: We found that consecutive acupuncture stimulations on BL62 affected the neural responses in a significant way, resulting in decreased activations during the second acupuncture stimulation. This is an important finding, suggesting that in future fMRI studies on acupuncture, researchers should take this methodological issue more seriously.