title: Neural basis of postural focus effect on concurrent postural and motor tasks: phase-locked electroencephalogram responses.
abstract: Dual-task performance is strongly affected by the direction of attentional focus. This study investigated neural control of a postural-suprapostural procedure when postural focus strategy varied. Twelve adults concurrently conducted force-matching and maintained stabilometer stance with visual feedback on ankle movement (visual internal focus, VIF) and on stabilometer movement (visual external focus, VEF). Force-matching error, dynamics of ankle and stabilometer movements, and event-related potentials (ERPs) were registered. Postural control with VEF caused superior force-matching performance, more complex ankle movement, and stronger kinematic coupling between the ankle and stabilometer movements than postural control with VIF. The postural focus strategy also altered ERP temporal-spatial patterns. Postural control with VEF resulted in later N1 with less negativity around the bilateral fronto-central and contralateral sensorimotor areas, earlier P2 deflection with more positivity around the bilateral fronto-central and ipsilateral temporal areas, and late movement-related potential commencing in the left frontal-central area, as compared with postural control with VIF. The time-frequency distribution of the ERP principal component revealed phase-locked neural oscillations in the delta (1-4Hz), theta (4-7Hz), and beta (13-35Hz) rhythms. The delta and theta rhythms were more pronounced prior to the timing of P2 positive deflection, and beta rebound was greater after the completion of force-matching in VEF condition than VIF condition. This study is the first to reveal the neural correlation of postural focusing effect on a postural-suprapostural task. Postural control with VEF takes advantage of efficient task-switching to facilitate autonomous postural response, in agreement with the "constrained-action" hypothesis.
authors.affiliation: School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei 100, Taiwan; Physical Therapy Center, National Taiwan University Hospital, Taipei 100, Taiwan.
authors.forename: Cheng-Ya
authors.initials: CY
authors.lastname: Huang
authors.affiliation: Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Chen-Guang
authors.initials: CG
authors.lastname: Zhao
authors.affiliation: Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan. Electronic address: ishwang@mail.ncku.edu.tw.
authors.forename: Ing-Shiou
authors.initials: IS
authors.lastname: Hwang
mesh_terms: D000328:Adult; D000842:Ankle / Q000294:innervation; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D003265:Contingent Negative Variation / Q000502:physiology; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D004856:Postural Balance; D011187:Posture / Q000502:physiology*; D025341:Principal Component Analysis; D011930:Reaction Time; D013997:Time Factors; D055815:Young Adult
keywords: Attentional focus; Event-related potential; Posture; Principal component analysis; Wavelet transformation