Objectives: The aim of this study was to investigate the delayed neuronal effects of acupuncture manipulations by observing blood oxygen level-dependent (BOLD) signal intensities.

Subjects: Fifteen (15) healthy, acupuncture-naive, right-handed subjects (all males; mean age, 23 years; range, 21-24 years) participated in this study. Design and interventions: Each subject was scanned in eight sessions that consisted of two repeated baseline scans (Period 1), two repeated scans with acupuncture stimulation at right LR2 (Period  2), two repeated scans with retention (Period 3), and two repeated scans after removal of the needle (Period 4).

Outcome measures: Sixteen (16) regions of interest (ROI) were defined. The BOLD signals for each session were obtained for  each ROI. A mixed-effects analysis of variance (ANOVA) test was performed in order to investigate the BOLD signal differences of the Periods in the 16 ROIs.

Results: The BOLD signal intensities increased in Periods 2 and 3, and then started to decrease in Period 4 in the right amygdala, supramarginal gyrus, temporal pole, and superior temporal gyrus. However, the BOLD signal intensity in Period 4 was significantly higher than that of Period 1. Especially, BOLD signal intensity was elevated promptly in the insula and the parahippocampal gyrus, whereas it was persistently elevated (delayed effect) in the amygdala.

Conclusions: BOLD signals were persistently elevated for at least 8 minutes after removal of the acupuncture needle or for at least 19 minutes after rotation of an acupuncture needle in some specific brain areas previously linked with LR2. In those specific brain ROIs, neuronal activation accompanying and following acupuncture showed both prompt and delayed effects.