Time‐varied characteristics of acupuncture effects in fMRI studies

Abstract

When studying the neural responses to acupuncture with a block-designed paradigm, its temporal dynamics predicted by the general linear model (GLM) conforms to typical "on-off" variations during a limited period of the experiment manipulation. Despite a lack of direct evidence associating its psychophysiological response, numerous clinical reports suggest that acupuncture can provide pain relief beyond a needling session. Therefore, a typical GLM analysis may be insensitive or inappropriate for identifying altered neural responses resulting from acupuncture. We developed a new approach to investigate the dynamics underlying sustained effects of acupuncture. Specifically, we designed two separate models to evaluate the baseline activities (prior to stimulation) and neural activities in sequential epochs, using three block-designed functional runs: acupuncture at acupoint ST36, nonmeridian point (NMP) stimulation, and a visual task. We found that the activity patterns during rest were associated with the stimulus types and that the resting activities might be even higher than that of stimulation phases. Such effects of the elevated activity during rest may reduce or eliminate the activity during stimulus conditions or even reverse the sign of brain activation using conventional GLM analysis. Moreover, such sustained responses, followed by acupuncture at ST36 and NMP, exhibited distinct patterns in wide brain structures, particularly in the limbic system and brainstem. These findings may pose great implications for the design and interpretation of a range of acupuncture neuroimaging studies.

Characterizing acupuncture stimuli using brain imaging with fMRI – a systematic review and meta-analysis of the literature

“…Of four studies, Bai et al [127] compared the stimulation phase and the resting phase of acupuncture stimulation and visual stimulation and found the BOLD signal returned to near-baseline values shortly after the visual stimulus, but for acupuncture stimulation the resting phase activities might be even higher than that of the stimulation phases. Table 1.…”

Spatiotemporal Modulation of Central Neural Pathway Underlying Acupuncture Action: A Systematic Review

“…The RVM has distinct but anatomically overlapping populations of modulatory neurons: off cells that inhibit and on cells that facilitate nociceptive transmission [46,47]. This could partially explain the RVM showed more complex (bidirectional) activity patterns as reported by [32]. Cells throughout this network could always fire simultaneously, implicating the PAG-RVM network functions as a unit and exerting discrete control, globally rather than topographically, over dorsal horn pain transmission neurons.…”

“…Due to the sustained effect of acupuncture, the temporal aspects of the BOLD response to acupuncture may violate the assumptions of the block-designed GLM estimates ( Fig. (1)) [32]. Thus, the magnitude of BOLD signal in rest period following the initial stimulation is unlikely to have returned to the initial (pre-stimulus) baseline level.…”

“…One pioneer study developed a novel approach (defining separate models) to evaluate the dynamic signal changes between the baseline activity (prior to stimulation) and the neural activity in sequential epochs within the multi-block design of acupuncture [32]. Results presented that acupuncture at ST 36 can induce significantly time-varied response patterns in the wider extent of the limbic-cerebellar and brainstem structures (Fig.…”

“…Row G: The BOLD responses in the cerebellum (anterior part -culmen and posterior part -declive) were positive predominantly, and negative afterwards (adapted from ref. [32]). reflecting a significant modulation of response directions during different stages of the acupuncture.…”