Fu Chen

Getting Your Sea Legs

Sea travel mandates changes in the control of the body. The process by which we adapt bodily control to life at sea is known as getting ones sea legs. We conducted the first experimental study of bodily control as maritime novices adapted to motion of a ship at sea. We evaluated postural activity (stance width, stance angle, and the kinematics of body sway) before and during a sea voyage. In addition, we evaluated the role of the visible horizon in the control of body sway. Finally, we related data on postural activity to two subjective experiences that are associated with sea travel; seasickness, and mal de debarquement. Our results revealed rapid changes in postural activity among novices at sea. Before the beginning of the voyage, the temporal dynamics of body sway differed among participants as a function of their (subsequent) severity of seasickness. Body sway measured at sea differed among participants as a function of their (subsequent) experience of mal de debarquement. We discuss implications of these results for general theories of the perception and control of bodily orientation, for the etiology of motion sickness, and for general phenomena of perceptual-motor adaptation and learning.

Nintendo Wii Balance Board is sensitive to effects of visual tasks on standing sway in healthy elderly adults

Research has shown that the Nintendo Wii Balance Board (WBB) can reliably detect the quantitative kinematics of the center of pressure in stance. Previous studies used relatively coarse manipulations (1- vs. 2-leg stance, and eyes open vs. closed). We sought to determine whether the WBB could reliably detect postural changes associated with subtle variations in visual tasks. Healthy elderly adults stood on a WBB while performing one of two visual tasks. In the Inspection task, they maintained their gaze within the boundaries of a featureless target. In the Search task, they counted the occurrence of designated target letters within a block of text. Consistent with previous studies using traditional force plates, the positional variability of the center of pressure was reduced during performance of the Search task, relative to movement during performance of the Inspection task. Using detrended fluctuation analysis, a measure of movement dynamics, we found that COP trajectories were more predictable during performance of the Search task than during performance of the Inspection task. The results indicate that the WBB is sensitive to subtle variations in both the magnitude and dynamics of body sway that are related to variations in visual tasks engaged in during stance. The WBB is an inexpensive, reliable technology that can be used to evaluate subtle characteristics of body sway in large or widely dispersed samples.

The effects of long-term resistance exercise on the relationship between neurocognitive performance and GH, IGF-1, and homocysteine levels in the elderly

This study aimed to investigate the effects of a long-term resistance exercise intervention on executive functions in healthy elderly males, and to further understand the potential neurophysiological mechanisms mediating the changes. The study assessed forty-eight healthy elderly males randomly assigned to exercise (n = 24) or control (n = 24) groups. The assessment included neuropsychological and neuroelectric measures during a variant of the oddball task paradigm, as well as growth hormone (GH), insulin-like growth factor-1 (IGF-1), and homocysteine levels at baseline and after either a 12 month intervention of resistance exercise training or control period. The results showed that the control group had a significantly lower accuracy rate and smaller P3a and P3b amplitudes in the oddball condition after 12 months. The exercise group exhibited improved reaction times (RTs), sustained P3a and P3b amplitudes, increased levels of serum IGF-1, and decreased levels of serum homocysteine. The changes in IGF-1 levels were significantly correlated with the changes in RT and P3b amplitude of the oddball condition in the exercise group. In conclusion, significantly enhanced serum IGF-1 levels after 12 months of resistance exercise were inversely correlated with neurocognitive decline in the elderly. These findings suggest that regular resistance exercise might be a promising strategy to attenuate the trajectory of cognitive aging in healthy elderly individuals, possibly mediated by IGF-1.

Specificity of Postural Sway to the Demands of a Precision Task at Sea.

Mariners actively adjust their body orientation in response to ship motion. On a ship at sea, we evaluated relations between standing postural activity and the performance of a precision aiming task. Standing participants (experienced mariners) maintained the beam from a handheld laser on a target. Targets were large or small, thereby varying the difficulty of the aiming task. Targets were located in front of the participant or to the participants right (requiring participants to look over the right shoulder), thereby varying the functional consequences (for the aiming task) of postural activity in different body axes. The torso was oriented toward the bow or toward the ships side (athwartship), thereby varying the effects on postural activity of differential motion of the ship in its different axes. The weather was rough, producing high magnitudes of ship motion, which sometimes caused participants to step or stagger. Our manipulations influenced the magnitude and dynamics of head and torso movements, as well as the organization of movement in different axes. The results provide the first empirical confirmation that postural activity can be influenced by orientation of the torso relative to a ship. Despite powerful effects of ship motion, postural activity was influenced by variations in target location and in the difficulty of the aiming task, replicating subtle effects that have been observed on land. We discuss implications for hull design and the placement of workstations on ships.

Postural responses to a suprapostural visual task among children with and without developmental coordination disorder

We sought to determine the effects of varying the perceptual demands of a suprapostural visual task on the postural activity of children with developmental coordination disorder (DCD), and typically developing children (TDC). Sixty-four (32 per group) children aged between 9 and 10 years participated. In a within-participants design, each child performed a signal detection task at two levels of difficulty, low (LD) and high difficulty (HD). During performance of the signal detection tasks we recorded positional variability of the head and torso using a magnetic tracking system. We found that task difficulty had a greater effect on task performance among the TDC group than among children with DCD. Overall positional variability was greater the DCD group than in the TDC group. In the TDC group, positional variability was reduced during performance of the HD task, relative to sway during performance of the LD task. In the DCD group, positional variability was greater during performance of the HD task than during performance of the LD task. In children, DCD may reduce the strength of functional integration of postural activity with the demands of suprapostural visual tasks.

Postural adaptations to a suprapostural memory task among children with and without developmental coordination disorder

Aim  The present study investigated the effects of varying the cognitive demands of a memory task (a suprapostural task) while recording postural motion on two groups of children, one diagnosed with developmental coordination disorder (DCD) and an age‐matched group of typically developing children.

Effects of cardiorespiratory fitness enhancement on deficits in visuospatial working memory in children with developmental coordination disorder: A cognitive electrophysiological study

The present study aimed to explore the effectiveness of chronic aerobic exercise intervention on the behavioral and neuroelectric performances of children with developmental coordination disorder (DCD) when carrying out a visuospatial working memory (VSWM) task. Twenty typically developing children and 40 children with DCD, equally divided into DCD-training and DCD nontraining groups, performed the cognitive task with concomitant event-related potential recording before and after 16 weeks of endurance training. Results indicated that the children with DCD displayed VSWM deficits with regard to behavioral performance (i.e., slower reaction time and low accuracy rate) and the neuroelectric indices (i.e., smaller P3 and pSW amplitudes) during the retrieval-process phase as reported in previous studies. However, after the exercise intervention, DCD-training group showed significantly higher accuracy rates and enhanced P3 amplitudes during the encoding and retrieval-process phases, compared with their pre-training performances. These findings suggest that increased cardiorespiratory fitness could effectively improve the performance of the VSWM task in children with DCD, by enabling the allocation of greater working memory resources related to encoding and retrieval.

Control of a Virtual Avatar Influences Postural Activity and Motion Sickness

The influence of vehicular control on motion sickness has implications for theories of motion sickness etiology. We asked whether motion sickness susceptibility might also be related to the control of non-vehicular locomotion. Participants were exposed to a console video game that featured ambulatory locomotion of a virtual avatar. In a yoked control design, individuals either played the game (players) or watched another participants recorded game play (viewers). Viewers were more likely than players to report motion sickness. During exposure to the video game players moved more than viewers, and the movement of players was more predictable or self-similar than the movement of viewers. Coupling of movement within player-viewer pairs was greater for pairs in which the viewer later reported motion sickness than for pairs in which both participants stated that they were not motion sick. The results reveal that motion sickness incidence can be influenced by the control of stimulus motion, in general, and is not limited to control of vehicular motion. We discuss implications of these findings for theories of motion sickness etiology.

Standing Posture on Land and at Sea

We studied the influence of ship motion on postural activity during stance, varying stance width (the distance between the feet in side-by-side stance) and the difficulty of visual tasks. Participants (experienced crewmembers) were tested on land and then on successive days on a ship at sea in mild sea states. On land, we replicated classical effects of stance width and visual task on the magnitude of postural movement. The magnitude of forces used in postural control was greater at sea than on land. Visual performance at sea was comparable to performance on land. Both stance width and visual task difficulty influenced postural activity at sea. In addition, postural activity changed over days at sea. We conclude that experienced crewmembers modulated standing posture in support of the performance of visual tasks and that such effects occurred even in mild sea states. The overall pattern of effects is compatible with the hypothesis that postural activity is modulated, in part, in support of the performance of suprapostural tasks.

A light fingertip touch reduces postural sway in children with autism spectrum disorders

UNLABELLED This study examined the effects of a light fingertip touch on postural control in children with autism spectrum disorders (ASD) and typically developing children (TDC). METHODS We recruited 16 children with ASD (age=11.041±1.275), and 16 TDC (age=10.966±1.166 years). A force platform measured postural sway in the anteroposterior (AP) and mediolateral (ML) directions under light fingertip touch (LT) and no touch (NT) conditions, with both eyes open (EO) and both eyes closed (EC). As a summary of the experimental conditions, ML sway was significantly greater in the ASD group than in the TDC group. Also, results showed a significant reduction in postural sway in the ML direction in the LT condition compared with the NT condition. These effects applied to both the EO and EC conditions. Lastly, the reduction in ML sway between the NT and LT conditions was significantly greater in the ASD than the TDC group. CONCLUSION The effects of a light fingertip touch on reducing postural sway appear more efficient in children with ASD compared with TDC. These findings suggest that a light fingertip touch may be of clinical and practical importance, and provides a useful means of enhancing postural stability in children with ASD.