Reduced influence of perceptual context in mild traumatic brain injury is not an illusion

Perceptual grouping is impaired following mild traumatic brain injury (mTBI). This may affect visual size perception, a process influenced by perceptual grouping abilities. We conducted two experiments to evaluate visual size perception in people with self-reported history of mTBI, using two different size-contrast illusions: the Ebbinghaus Illusion (Experiment 1) and the Müller-Lyer illusion (Experiment 2). In Experiment 1, individuals with mTBI and healthy controls were asked to compare the size of two target circles that were either the same size or different sizes. The target circles appeared by themselves (no-context condition), or were surrounded by smaller or larger circles (context condition). Similar levels of accuracy were evident between the groups in the no-context condition. However, size judgements by mTBI participants were more accurate in the context condition, suggesting that they processed the target circles separately from the surrounding circles. In Experiment 2, individuals with mTBI and healthy controls judged the length of parallel lines that appeared with arrowheads (context condition) or without arrowheads (no context condition). Consistent with Experiment 1, size judgements by mTBI participants were more accurate than size judgements by control participants in the context condition. These findings suggest that mTBI influences size perception by impairing perceptual grouping of visual stimuli in near proximity

Psychophysical effects of subtle modification of the built environment: a quasi-experimental field study

Background: China’s rapid urban growth is associated with an increasingly unhealthy population. Urban planners can design cities to promote healthy lifestyles, but to re-engineer the existing built environment is no simple task. We assessed whether a simple modification of the built environment was associated with altered perceptions of, and ambulation in, that environment. Methods: We adjusted a single-rail stair banister (length 3 m, height 1 m) in an urban area of Hong Kong, China, to increase or decrease the convergence angle with the stairs by 10% (plus or minus 1.91°). When positioned conventionally, the banister was parallel to the stairs (2.19 m width, 26.5° incline). 92 participants (mean age 19.71 [0.79], 54 male and 38 female) who were unaware that the banister diverged from (n=32), converged with (n=30), or was parallel to the stairs (n=30), visually estimated the angle of incline of the stairs from the top by rotating a disk to match the slant of the staircase. Walking speed (metres per second) was video-recorded surreptitiously as a sub-sample of the participants (n=36) approached the stairs with the banister in each position. Data were analysed using one-way analysis of variance followed by Bonferroni comparisons. Ethical approval of the study was obtained from the University of Hong Kong Research Ethics Committee, and participants provided written informed consent to participate. Findings: Visual estimations differed between the groups (F2,70=3.11, p=0.05, ηp2=0.08); estimates of angle were smaller when the banister converged with the stairs (32.53 [8.39]°) than when it diverged (39.69 [9.50]°) (p=0.007) or was parallel (39.88 [8.92]°) (p=0.006). Walking speeds in the final three strides preceding transition to stair descent also differed (F2,70,70=3.11, p=0.05, ηp2=0.08) with mean walking speed slower when the banister diverged (1.24 [0.26] m/s) than when it converged (1.36 [0.19] m/s) (p=0.046). Interpretation: Modification of the angle of a stair banister was associated with differences in perception of the steepness of stairs and in walking behavior during approach to the stairs. Problems associated with rapid urban development, including falls in older people and physical inactivity, are high on the health agenda of the Chinese government. Future work should examine whether stairs that appear less steep are more readily climbed, thus promoting physical activity, and whether stepping parameters are improved, thus promoting fewer falls

Examining Movement-Specific Reinvestment and Performance in Demanding Contexts.

Two experiments examined the roles of the dimensions of movement-specific reinvestment (movement self-consciousness and conscious motor processing) on performance under demanding conditions. In Experiment 1, novice golfers practiced a golf putting task and were tested under low- and high-anxiety conditions. Conscious motor processing was not associated with putting proficiency or movement variability; however, movement self-consciousness was positively associated with putting proficiency and appeared to be negatively associated with variability of impact velocity in low-anxiety conditions, but not in high-anxiety conditions. Increased anxiety and effort possibly left few attention resources for movement self-consciousness under high anxiety. In Experiment 2, participants performed a quiet standing task in single- and dual-task conditions. Movement self-consciousness was positively associated with performance when attention demands were low (single task) but not when attention demands were high (dual task). The findings provide insight into the differential influence of the two dimensions of movement-specific reinvestment under demanding conditions

A preliminary investigation into the efficacy of training soccer heading in immersive virtual reality

Recent research has suggested a link between repetitive soccer heading and the increased incidence of neurodegenerative disease in retired players. In response, restrictions have been introduced to limit the amount of soccer heading in training and competitive matches. Therefore, while heading remains an integral part of the game, players are restricted in the amount of training that they can gain on this important skill without potentially harming their long-term wellbeing. The aim of this study was to provide a preliminary investigation into the efficacy of training soccer heading in immersive virtual reality (VR) which allows the practice of the skill without the risk of repetitive head impacts. Thirty-six recreational soccer players were divided into a VR group (n = 18) who trained soccer heading on three occasions over a 7–10-day period in VR and a control group (n = 18) who received no training in soccer heading. Measures of real-world heading performance (i.e. the number of goals scored and shot accuracy), perceived confidence and perceived self-efficacy were assessed pre- and post-training. The results showed that the VR group experienced significant improvements in the number of goals scored and increased their perceptions of confidence and self-efficacy. These results show preliminary support for the inclusion of VR-based training in soccer heading where players can hone their heading skills without exposure to repeated head impacts. Implications and practical applications are discussed

Propensity for movement specific reinvestment by physiotherapists: Implications for education

© 2018 Taylor & Francis. Previous studies have shown that the propensity for conscious monitoring and control of movement (i.e. movement specific reinvestment) influences the acquisition of movement skills. Physiotherapists, whose primary function is to promote effective human movement, also develop specialized movement skills that are necessary to perform diagnostic and therapeutic procedures. To explore the implications for promoting expertise, this current study examined physiotherapists’ propensity for movement-specific reinvestment. Practitioners and students in physiotherapy, and other rehabilitation, and non-health professionals, completed the Movement Specific Reinvestment Scale, which measures two dimensions of reinvestment: 1) conscious motor processing (CMP); and 2) movement self-consciousness (MS-C). Physiotherapists scored significantly higher than other professionals on both CMP and MS-C. Specifically among physiotherapists, those with relatively fewer years of practice tended to have higher MS-C scores. Movementspecific reinvestment appears to be a characteristic of physiotherapists that could be relevant for understanding the ways in which novices think and act as they progress to expertise. Further research is recommended to examine the role of reinvestment in performance of different tasks of varying complexity by novice physiotherapists

The effect of unilateral hand contractions on psychophysiological activity during motor performance: Evidence of verbal-analytical engagement

Objectives: Conscious engagement in movement control can influence motor performance. In most cases, the left hemisphere of the brain plays an important role in verbal-analytical processing and reasoning, so changes in the balance of hemispheric activation may influence conscious engagement in movement. Evidence suggests that unilateral hand contractions influence hemispheric activation, but no study has investigated whether there is an associated effect of hand contractions on verbal-analytical processing during motor performance. This study utilized psychophysiological (and behavioural) measures to examine whether pre-performance unilateral hand contraction protocols change verbal-analytical engagement during motor performance. Design: A repeated measures crossover design was employed. Methods: Twenty-eight participants completed three hand contraction protocols in a randomised order: left-, right- and no-hand contractions. Electroencephalography (EEG) measures of hemispheric asymmetry were computed during hand contractions. A golf putting task was conducted after each protocol. EEG connectivity between sites overlying the left verbal-analytical temporal region (T7) and the motor planning region (Fz) was computed for the 3 sec prior to movement initiation. Additionally, electrocardiography (ECG) and electromyography (EMG) signals were analysed 6 sec prior to movement initiation until 6 sec after. Golf putting performance (distance from the target) and putter swing kinematics were measured. Results: Contralateral hemisphere activity was revealed for the left-hand and right-hand contraction conditions. During motor planning, the left-hand contraction protocol led to significantly lower T7-Fz connectivity, and the right-hand contraction protocol led to significantly higher T7-Fz connectivity than the other conditions. EMG, ECG and kinematic measures did not differ as a function of condition. Importantly, T7-Fz connectivity mediated the relationship between hand squeezing and motor performance (distance from the target). Conclusion: The EEG results suggest that pre-performance unilateral hand contractions influence the extent of verbal-analytical engagement during motor planning, which in turn influences motor performance. However, the hand contractions did not influence cardiac activity, muscle activity or kinematics

The Effects of Fatigued Working Memory Functions on Hypothesis Testing During Acquisition of a Motor Skill

Implicit motor learning paradigms aim to minimize verbal-analytical engagement in motor performance. Some paradigms do this by decreasing working memory activity during practice, which reduces explicit processes associated with the search for motor solutions (e.g., hypothesis testing). Here we designed a mentally demanding motor task to fatigue working memory prior to motor practice and then tested whether it reduced hypothesis testing. Fifty-nine participants were randomly assigned to complete the mentally demanding motor task (cognitive fatigue group) or to complete an undemanding motor task (nonfatigued control group). Feelings of fatigue, working memory functions, electroencephalography (EEG) Fz power, and vagal control were assessed pre and posttask to quantify the effect of the mentally demanding motor task on cognitive fatigue. Thereafter, an adapted shuffleboard task was completed to determine the impact on hypothesis testing. Hypothesis testing was assessed by self-report, technique changes, and equipment-use solutions. Additionally, verbal-analytical engagement in motor performance was (indirectly) gauged with EEG T7-Fz connectivity and T7 power measures. Participants in the cognitive fatigue group reported more fatigue and displayed moderated working memory functions and Fz theta power. During practice of the shuffleboard task, participants also displayed more technique changes and higher verbal-analytical engagement in motor planning (EEG T7-Fz connectivity), compared with participants in the control group. The mentally demanding motor task suppressed workingmemory functions, but resulted in more, rather than less, hypothesis testing during shuffleboard practice. The implications are discussed in the context of implicit motor learning theory

Movement specific reinvestment and allocation of attention by older adults during walking

© 2015, Marta Olivetti Belardinelli and Springer-Verlag Berlin Heidelberg. Older repeat fallers have previously been shown to have a higher propensity to consciously monitor and control their movements (i.e. reinvestment) than non-fallers, yet to direct their attention equally between their limb movements and the external environment during locomotion (Wong et al. in J Am Geriatr Soc 57: 920–922, 2009). Whether increased attention to their movements is a result of falling or originates from a prior inclination to reinvest remains unclear. In order to better understand the interaction between reinvestment and attention during locomotion, this study examined the allocation of attention by older adults who had not fallen but displayed a high or low inclination for reinvestment. Twenty-eight low and twenty-eight high reinvestors were required to perform 30 walking trials. Their allocation of attention during walking was evaluated by asking tone-related attentional focus questions shortly after finishing each walking trial. High reinvestors were found to be more aware of their limb movements and less aware of the external environment. Low reinvestors, on the contrary, were more aware of the surrounding environment and less aware of their movement mechanics. Given that focusing internally to body movements has been proposed to utilise working memory capacity, the ability of high reinvestors to pick up all the environmental information necessary for successful locomotion might be compromised and requires further examination

A tool for measuring mental workload during prosthesis use: The Prosthesis Task Load Index (PROS-TLX)

When using a upper-limb prosthesis, mental, emotional, and physical effort is often experienced. These have been linked to high rates of device dissatisfaction and rejection. Therefore, understanding and quantifying the complex nature of workload experienced when using, or learning to use, a upper-limb prosthesis has practical and clinical importance for researchers and applied professionals. The aim of this paper was to design and validate a self-report measure of mental workload specific to prosthesis use (The Prosthesis Task Load Index; PROS-TLX) that encapsulates the array of mental, physical, and emotional demands often experienced by users of these devices. We first surveyed upper-limb prosthetic limb users who confirmed the importance of eight workload constructs taken from published literature and previous workload measures. These constructs were mental demands, physical demands, visual demands, conscious processing, frustration, situational stress, time pressure and device uncertainty. To validate the importance of these constructs during initial prosthesis learning, we then asked able-bodied participants to complete a coin-placement task using their anatomical hand and then using a myoelectric prosthesis simulator under low and high mental workload. As expected, using a prosthetic hand resulted in slower movements, more errors, and a greater tendency to visually fixate the hand (indexed using eye-tracking equipment). These changes in performance were accompanied by significant increases in PROS-TLX workload subscales. The scale was also found to have good convergent and divergent validity. Further work is required to validate whether the PROS-TLX can provide meaningful clinical insights to the workload experienced by clinical users of prosthetic devices

Acquiring visual information for locomotion by older adults: A systematic review

© 2015. Developments in technology have facilitated quantitative examination of gaze behavior in relation to locomotion. The objective of this systematic review is to provide a critical evaluation of available evidence and to explore the role of gaze behavior among older adults during different forms of locomotion. Database searches were conducted to identify research papers that met the inclusion criteria of (1) study variables that included direct measurement of gaze and at least one form of locomotion, (2) participants who were older adults aged 60 years and above, and (3) reporting original research. Twenty-five papers related to walking on a straight path and turning (n = 4), stair navigation (n = 3), target negotiation and obstacle circumvention (n = 13) and perturbation-evoked sudden loss of balance (n = 5) were identified for the final quality assessment. The reviewed articles were found to have acceptable quality, with scores ranging from 47.06% to 94.12%. Overall, the current literature suggests that differences in gaze behavior during locomotion appear to change in late adulthood, especially with respect to transfer of gaze to and from a target, saccade-step latency, fixation durations on targets and viewing patterns. These changes appear to be particularly pronounced for older adults with high risk of falling and impaired executive functioning