Plasticity In Acupuncturists Brain: The Magnetic Resonance Imaging Based Study

The brain, as the source of human behavior, is by design molded by environmentalchanges and pressures, physiologic modifications, and experiences. We strongly suggestthat plasticity is an intrinsic property of the nervous system retained throughout alifespan and that it is not possible to understand normal psychological function or themanifestations or consequences of disease without invoking the concept of brainplasticity. This is the mechanism for learning and for growth anddevelopment—changes in the input of any neural system, or in the targets or demandsof its efferent connections, lead to system reorganization that might be demonstrable atthe level of behavior, anatomy, and physiology and down to the cellular and molecularlevels.Human brain plasticity is the basis from human learning and memory. With thedevelopment of neuroimaging techniques, it is possible to researchers to locate changesand alterations in the grey matters and white mattes as well as functional features. Inrecent decades, a series of studies using fMRI focus on this issue in the context ofneuroplasticity. Among all research subjects, experts have received much scientificattention, in that expertise represents the level par excellence for human learning.Several expertise models have been brought up by different research groups to studyundetermined issue in the field of perceptual learning, motor learning and cognitivelearning. A British group established the expertise model of London taxi driver to studyhippocampus role in spatial navigation. German groups have proposed the model ofprofessional musicians to study the perceptual-motor learning mechanism. And themodel of meditators is introduced to study higher-order cognitive functions, such asattention direction and cognitive control.Each acupuncturist is a living literature of traditional Chinese medicinal practices andbelieves. They are not only practitioners but also explorers in the way human bodyreciprocates with the mental and physical world. Acupuncture skills are gained throughextended years of practice and abundant clinical practice. We do hope our studies mayhave ramifications for tactile-motor rehabilitation. The major contributions have beenlisted below:We have proposed the behavioral expertise model of acupuncturists. Acupuncturistshave unique behavioral expertise, e.g.1) exceptional tactile discrimination ability forthe functioning digits which enable the acupuncture practitioners to distinguish subtle dynamic changes of manipulation sensation transmitted through fine needles due to apatient’s constantly changing bodily response to each round of needling manipulation;2)the ability of making precise and prompt adjustment in generating motorplans/commands for the following round of finger manipulation to achieve optimalclinical outcomes;3) the execution of motor plans/commands into coordinated and finefinger movements.4) emotion regulatory skills which operates in acupuncturists whoinflict painful procedures in their daily practice with patients in order to preventnegative emotions from impairing their capacity of assistance. A cohort group of highlytrained acupuncturists and non-acupuncturists were recruited and a series ofpsychophysical approaches, cognitive task and behavioral task were used to verify theabove-mentioned model. Our analysis proved the robustness of expertise in all threedomains in acupuncturist, which implicates that the behavioral expertise model is valid.Given the previous literature,‘practice makes perfect’ cannot simply explain whathappened. The key reason is structural/functional alterations in experts’ brains duringthe process of skill acquisition, i.e. the formation of ‘expert system’ in brain, in terms ofmorphological (the grey matter and the white matter) changes and functional alterations(the response amplitude and pattern under tasks). Therefore, we investigate howexpertise-related effect affects patterns of local spontaneous activity in resting brain andhow these features are linked with the behavioral expertise. We investigated thehomogeneity of local blood oxygen level-dependent fluctuations in the resting stateusing a regional homogeneity (ReHo) analysis among16acupuncturists and16matchednon-acupuncturists (NA). To prove acupuncturists’ expertise, we utilized a series ofpsychophysical tests. Our results demonstrated that, acupuncturists significantlyoutperformed NA in tactile-motor and emotional regulation domain and theacupuncturist group showed increased coherence in local BOLD signal fluctuations inthe left primary motor cortex (MI), the left primary somatosensory cortex (SI) and theleft ventral medial prefrontal cortex/orbitofrontal cortex (VMPFC/OFC). Regressionanalysis displayed that, in the acupuncturists group, ReHo of VMPFC/OFC couldpredict behavioral outcomes, evidenced by negative correlation between unpleasantnessratings and ReHo of VMPFC/OFC and ReHo of SI and MI positively correlated withthe duration of acupuncture practice. We suggest that expertise could modulate patternsof local resting state activity by increasing regional clustering strength, which is likelyto contribute to advanced local information processing efficiency. Our study completesthe understanding of neuroplasticity changes by adding the evidence of local restingstate activity alterations, which is helpful for elucidating in what manner training effect extends beyond resting state.Then, we are interested in how acupuncturists respond to specific external stimulibehaviorally and centrally. Accordingly, we would like to see how two groups of peoplerespond to noxious stimuli, i.e. acupuncture stimulation over left ST36and howexpertise contributes to this process. Therefore, we invited25acupuncturists and25matched controls. Our behavioral analysis showed that although both groups haveshown similar ratings of Deqi, the acupuncturists group gave significantly lower ratingsof unpleasantness, which explicated that they had better emotional regulationproficiency in the face of noxious bodily stimulation. We used multivariate patternanalysis (MVPA) and pair-wise correlation to identify the brain regions showingdifferent response patterns and how these regions work with one another. Our resultsshowed that brain regions responsible for processing of bodily sensation, such as insulaand the secondary somatosensory cortex and emotion regulation, such as VMPFC,DLPFC and ACC showed distinctive response patterns between groups, and theseregions worked in a network manner in acupuncturists group, whereas no such effectswere identified in the non-acupuncturists group. We further supposed that thedifferentiations were linked with the expertise which acquired through years ofacupuncture training. In the following study, a more practical question is to be askedthat how findings from this study can benefit the clinical outcomes and treatment ofpatients in real world.Furthermore, we asked the question that whether long years of training can inducemorphological changes in the acupuncturists’ brain and how these changes are related totraining and behavioral expertise. Therefore, cohorts of22acupuncturists and22non-acupuncturists were recruited. Behavioral tests were delivered to assess theacupuncturists’ behavioral expertise. The results confirmed acupuncturists’ tactile-motorskills and emotion regulation proficiency compared to non-acupuncturists. Using thevoxel-based morphometry technique, we revealed larger grey matter volumes inacupuncturists in the hand representation of the contralateral SI, the right lobule V/VIand the bilateral ventral anterior cingulate cortex/ventral medial prefrontal cortex. Greymatter volumes of the SI and Lobule V/VI positively correlated with the duration ofacupuncture practice. To our best knowledge, this study provides first evidence for theanatomical alterations in acupuncturists, which would possibly be the neural correlatesunderlying acupuncturists’ exceptional skills. Future longitudinal study is necessary toestablish the presence and direction of a causal link between practice/use and brainanatomy. In sum, our current research converges under the topic of how procedural learning andcontributes to the acquisition of expertise of acupuncturists and in return how further thelearning effects, i.e. central representations facilitate the retention and maintenance oftheir expertise. We suggest that our former analysis has identified a possible foundationon which further studies can proceed. We also suggest that the model of highly trainedacupuncturists is potentially beneficial to plasticity research on tactile and emotionregulation domains.