Xu Dayuan, Shin Narae, Lee Sungjun, Park Jaebum
Department of Physical Education, Seoul National University, Seoul, South Korea.
Institute of Sport Science, Seoul National University, Seoul, South Korea.
Front Hum Neurosci. 2021 Oct 18;15:721679. doi: 10.3389/fnhum.2021.721679. eCollection 2021.
Behavioral stability partially depends on the variability of net outcomes by means of the co-varied adjustment of individual elements such as multi-finger forces. The properties of cyclic actions affect stability and variability of the performance as well as the activation of the prefrontal cortex that is an origin of subcortical structure for the coordinative actions. Little research has been done on the issue of the relationship between stability and neuronal response. The purpose of the study was to investigate the changes in the neural response, particularly at the prefrontal cortex, to the frequencies of isometric cyclic finger force production. The main experimental task was to produce finger forces while matching the produced force to sine-wave templates as accurately as possible. Also, the hemodynamics responses of the prefrontal cortex, including oxy-hemoglobin concentration (ΔHbO) and the functional connectivity, were measured using functional near-infrared spectroscopy. The frequency conditions comprised 0.1, 1, and 2 Hz. The uncontrolled manifold (UCM) approach was applied to compute synergy indices in time-series. The relative phase (RP), the coefficient of variation (CV) of the peak and trough force values were computed as the indices of performance accuracy. The statistical parametric mapping (SPM) was implemented to compare the synergy indices of three frequency conditions in time-series. A less accurate performance in the high-frequency condition was caused not by the RP, but mainly by the inconsistent peak force values (CV; < 0.01, = 0.90). The SPM analysis revealed that the synergy indices were larger in the low-frequency than in high-frequency conditions. Further, the ΔHbO remained unchanged under all frequency conditions, while the functional connectivity decreased with an increase in the frequency of cyclic force production. The current results suggested that the concurrent activation of the prefrontal region mainly depends on the frequency of cyclic force production, which was associated with the strength of stability indices and performance errors. The current study is the first work to uncover the effect of frequency on the multi-finger synergies as to the hemodynamic response in the prefrontal cortex, which possibly provides a clue of the neural mechanism of synergy formation and its changes.
行为稳定性部分取决于通过多手指力量等个体元素的协变调整实现的净结果变异性。循环动作的特性会影响表现的稳定性和变异性，以及前额叶皮层的激活，前额叶皮层是协调动作的皮层下结构的起源。关于稳定性与神经元反应之间关系的研究较少。本研究的目的是调查神经反应的变化，特别是前额叶皮层对等长循环手指力量产生频率的反应变化。主要实验任务是在尽可能精确地将产生的力量与正弦波模板匹配的同时产生手指力量。此外，使用功能近红外光谱测量前额叶皮层的血液动力学反应，包括氧合血红蛋白浓度（ΔHbO）和功能连接性。频率条件包括0.1、1和2赫兹。应用非受控流形（UCM）方法计算时间序列中的协同指数。计算相对相位（RP）、峰值和谷值力值的变异系数（CV）作为表现准确性的指标。实施统计参数映射（SPM）以比较三个频率条件在时间序列中的协同指数。高频条件下表现不太准确不是由RP引起的，而是主要由峰值力值不一致（CV；<0.01，=0.90）引起的。SPM分析表明，低频条件下的协同指数大于高频条件下的。此外，在所有频率条件下，ΔHbO保持不变，而功能连接性随着循环力产生频率的增加而降低。当前结果表明，前额叶区域的同时激活主要取决于循环力产生的频率，这与稳定性指数的强度和表现误差相关。当前研究是第一项揭示频率对前额叶皮层血液动力学反应中多手指协同作用影响的工作，这可能为协同形成及其变化的神经机制提供线索。
