Effect of Postural Control Demands on Early Visual Evoked Potentials during a Subjective Visual Vertical Perception Task in Adolescents with Idiopathic Scoliosis.

Yi-Tzu Chang,Chi-Wen Lung,Jen-Suh Chern,Ling-Fu Meng,Po-Liang Lai,Chun-Ju Chang

doi:10.3389/fnhum.2017.00326

Abstract

Subjective visual vertical (SVV) judgment and standing stability were separately investigated among patients with adolescent idiopathic scoliosis (AIS). Although, one study has investigated the central mechanism of stability control in the AIS population, the relationships between SVV, decreased standing stability, and AIS have never been investigated. Through event-related potentials (ERPs), the present study examined the effect of postural control demands (PDs) on AIS central mechanisms related to SVV judgment and standing stability to elucidate the time-serial stability control process. Thirteen AIS subjects (AIS group) and 13 age-matched adolescents (control group) aged 12–18 years were recruited. Each subject had to complete an SVV task (i.e., the modified rod-and-frame [mRAF] test) as a stimulus, with online electroencephalogram recording being performed in the following three standing postures: feet shoulder-width apart standing, feet together standing, and tandem standing. The behavioral performance in terms of postural stability (center of pressure excursion), SVV (accuracy and reaction time), and mRAF-locked ERPs (mean amplitude and peak latency of the P1, N1, and P2 components) was then compared between the AIS and control groups. In the behavioral domain, the results revealed that only the AIS group demonstrated a significantly accelerated SVV reaction time as the PDs increased. In the cerebral domain, significantly larger P2 mean amplitudes were observed during both feet shoulder-width-apart standing and feet together standing postures compared with during tandem standing. No group differences were noted in the cerebral domain. The results indicated that (1) during the dual-task paradigm, a differential behavioral strategy of accelerated SVV reaction time was observed in the AIS group only when the PDs increased and (2) the decrease in P2 mean amplitudes with the increase in the PD levels might be direct evidence of the competition for central processing attentional resources under the dual-task postural control paradigm.

Highlights

Adolescent idiopathic scoliosis (AIS) is the most common type of spinal deformity among juveniles (Weinstein, 1994)
The present study investigated the effect of postural control demands (PDs) on the subjective visual vertical (SVV) performances of the AIS and control groups to illuminate the cortical mechanism of postural control
The Cobb angle in 9 of the 13 subjects in the AIS group was characterized by a right thoracic–left lumbar scoliosis curve, whereas the other four AIS subjects were characterized by a left thoracic–right lumbar scoliosis curve

Summary

Introduction

Adolescent idiopathic scoliosis (AIS) is the most common type of spinal deformity among juveniles (Weinstein, 1994). In 1985, Herman et al suggested that the vestibular signals interpreted by the CNS were highly correlated to the magnitude of the deviation associated with the curvature of the spine and may be an underlying factor for the high percentage of learning problems among AIS subjects. They further indicated that the presence of visuospatial perceptual impairment may be a common feature of idiopathic scoliosis. Little attention has been paid to the role of the cerebral domain in the CNS, which might result in altered functional behavior after the occurrence or progression of scoliosis (Herman et al, 1985; Cheung et al, 2002; Beaulieu et al, 2009)

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Discussion

Conclusion