Abstract
BackgroundWe investigated developmental changes in shortening of pro-saccade reaction time while maintaining neck flexion.MethodsSubjects comprised 135 children (3–14 years) and 29 young adults (19–23 years). Children were divided into six groups in 2-year age strata. Pro-saccade reaction tasks for 30 s were performed in neck rest and flexion positions. Reaction times under each position were averaged in every 10-s period.ResultsUnder neck rest position, reaction time in the 0–10 s period was significantly longer in the 3- to 4-year-old group than in the 5- to 6-year-old group and above. No significant age effect was found for reaction time in the 0–10 s period in the 5- to 6-year-old group and above. Although a significant effect of neck flexion was not observed until the 9- to 10-year-old group, significant shortening of reaction time with neck flexion was found in the 11- to 12-year-old group and above. Furthermore, this shortening was maintained until the first 20–s period in the 11- to 12-year-old group and during the entire 30 s in the 13- to 14-year-old and above.ConclusionsThese results suggest that brain activation with the maintenance of neck flexion, related to shortening of the pro-saccade reaction time, was found from a later age of approximately 11 years and above, compared with the age at which information-processing function in the pro-saccade was enhanced. In addition, brain activation with the maintenance of neck flexion was sustained longer with age.
Highlights
We investigated developmental changes in shortening of pro-saccade reaction time while maintaining neck flexion
We reported that pro-saccade reaction time shortened with voluntary isometric contraction of the superficial neck extensors by shoulder girdle elevation [22], or with vibration stimulation to the trapezius, one of the superficial neck
Kunita et al Journal of Physiological Anthropology (2018) 37:2 extensors [23, 24]. These findings suggest that the shortening with maintaining neck flexion posture is attributable to an ascending brain activation system in tandem with increases in muscle afferent information [25,26,27]
Summary
We investigated developmental changes in shortening of pro-saccade reaction time while maintaining neck flexion. Saccadic eye movements are often used to quickly and precisely shift the gaze to an appearing visual target Such eye movement is called visually guided saccade, or pro-saccade. We have previously reported that maintaining a flexed neck position, which constitutes part of the dynamic posture [19], leads to shortening of the pro-saccade reaction time [20, 21]. This shortening was observed without the chin resting on a stand, so the neck extensors would have been activated [20]. We reported that pro-saccade reaction time shortened with voluntary isometric contraction of the superficial neck extensors by shoulder girdle elevation [22], or with vibration stimulation to the trapezius, one of the superficial neck
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