The influence of action execution on end-state comfort and underlying movement kinematics: An examination of right and left handed participants

Does aging amplify the rule-based efficiency effect in action selection?

When it comes to the selection of adequate movements, people may apply varying strategies. Explicit if-then rules, compared to implicit prospective action planning, can facilitate action selection in young healthy adults. But aging alters cognitive processes. It is unknown whether older adults may similarly, profit from a rule-based approach to action selection. To investigate the potential effects of aging, the Rule/Plan Motor Cognition (RPMC) paradigm was applied to three different age groups between 31 and 90 years of age. Participants selected grips either instructed by a rule or by prospective planning. As a function of age, we found a general increase in a strategy-specific advantage as quantified by the difference in reaction time between plan- and rule-based action selection. However, in older age groups, these differences went in both directions: some participants initiated rule-based action selection faster, while for others, plan-based action selection seemed more efficient. The decomposition of reaction times into speed of the decision process, action encoding, and response caution components suggests that rule-based action selection may reduce action encoding demands in all age groups. There appears a tendency for the younger and middle age groups to have a speed advantage in the rule task when it comes to information accumulation for action selection. Thus, one influential factor determining the robustness of the rule-based efficiency effect across the lifespan may be presented by the reduced speed of information uptake. Future studies need to further specify the role of these parameters for efficient action selection.

Selective effects of psychosocial stress on plan based movement selection

Efficient movement selection is crucial in everyday activities. Whether this function is governed by our stress system is so far unknown. In the current study, data from thirty-six young male adults were analyzed. They performed rule- and plan-based movement selection tasks before (session 1) and after (session 2) a psychosocial stressor, or after a control condition without additional social stressor. Results showed that the rule-based efficiency advantage which was observed prior to the psychosocial stressor was significantly reduced afterwards in the whole sample, as well as in the stress group. Regression analyses revealed that this effect was due to a modulation of the plan-based approach. Especially variations-both increase and decrease-in the parasympathetic activity (reflected by the heart rate variability measure RMSSD) appeared to be disadvantageous for plan-based movement selection improvement. In contrast, performance in the rule-based movement selection tasks appeared to be rather invariant to external influences. The current results suggest that autonomic nervous system activity might modulate motor-cognitive performance. This modulatory capability might be selective for plan-based approaches, hence the applied strategy to movement selection could be decisive when it comes to the vulnerability of motor-cognitive processes towards psychosocial stress.

Investigating motor planning in children with DCD: Evidence from simple and complex grip-selection tasks

Several studies suggest that children with Developmental Coordination Disorder (DCD) may be able to plan simple movements as well as their peers, but experience increasing difficulties as the movements become complex. The present study aimed to clarify the nature of motor planning in DCD, including a putative deficit, by being the first to investigate motor planning using converging measures of simple and complex motor planning in a single sample of children with DCD. Boys aged between 8 and 12 years with (n = 10) and without DCD (n = 17) completed three commonly used 'simple' (bar grasping, sword, and bar transport tasks) measures and one 'complex' (octagon task) measure of end-state-comfort (ESC), a classic measurement of motor planning ability. To achieve ESC when manipulating an object, a person may choose to start with an uncomfortable grip in order to end the movement in a comfortable position. Results indicate that the participants with DCD planned for ESC as efficiently as their peers when performing the 'simple' measures of ESC but were significantly less likely to end their performances in ESC than those without DCD for the more 'complex' octagon task. Taken together, our data suggest that school-aged children with DCD may be able to plan simple movements as efficiently as their peers, but have more difficulty doing so for multi-movement or complex sequences. Based on the assumption that the efficiency of such motor planning is dependent on the integrity of internal modelling systems, we argue that our study provides indirect support for the internal modelling deficit hypothesis.

The effect of aging and contextual information on manual asymmetry in tool use

Healthy aging affects manual asymmetries in simple motor tasks, such as unilateral reaching and aiming. The effects of aging on manual asymmetries in the performance of a complex, naturalistic task are unknown, but are relevant for investigating the praxis system. This study examined how aging influences manual asymmetry in different contexts in a tool manipulation task. Fifty healthy, right-hand-dominant young (N = 29; 21.41 ± 2.87 years), and elderly (N = 21; mean: 74.14 ± 6.64 years) participants performed a 'slicing' gesture in response to a verbal command in two contexts: with (tool) and without the tool (pantomime). For interjoint relationships between shoulder plane of elevation and elbow flexion, a HAND × AGE × CONTEXT interaction existed (F_1,43 = 4.746, p = 0.035). In pantomime, interjoint control deviated more in the left (non-dominant) than the right (dominant) limb in the elderly adult group (Wilcoxon, p = 0.010). No such differences existed in the young adult group (Wilcoxon, p = 0.471). Furthermore, contextual information reduced interjoint deviation in young adults when the task was performed with the right (dominant) hand (Wilcoxon, p = 0.001) and in the elderly adults when the task was performed with the left (non-dominant) hand (Wilcoxon, p = 0.012). The presence of the tool did not reduce interjoint deviation for the right hand in the elderly group (Wilcoxon, p = 0.064) or the left hand in the young group (Wilcoxon, p = 0.044). Deviation within trials (i.e., intrasubject deviation) in elbow flexion was higher in the elderly relative to the young adult group (p = 0.003). Finally, resultant peak velocities were smaller (p = 0.002) and cycle duration longer (p < 0.0001) in the elderly adult group. This study provides novel evidence that aging affects manual asymmetries and sensorimotor control in a naturalistic task and warrants that aging research considers the context in which the task is performed.

End-state comfort in two object manipulation tasks: Investigating how the movement context influences planning in children, young adults, and older adults

The movement context (pantomime, pantomime with image/object as guide, and actual use) has been shown to influence end-state comfort-the propensity to prioritize a comfortable final hand position over an initially comfortable one-across the lifespan. The present study aimed to assess how the movement context (pantomime, using a dowel as the tool, and actual use) influences end-state comfort when acting with objects (glass/hammer) that differ in use-dependent experience. Children (ages 6-11, n = 70), young adults (n = 21), and older adults (n = 21) picked up an overturned glass to pour water and a hammer to hit a nail, where the handle faced away from the participant. End-state comfort was assessed in each movement context. Findings provide support for an increase in end-state comfort with age, adult-like patterns at age 10, and no difference between older adults and 8- to 9-year-old children. In addition, this work revealed that perception of "graspability" led to an increase in end-state comfort in the hammering task; therefore, suggesting our ability to act with objects and tools in the environment is influenced by use-dependent experience and object perception. Results add to our understanding of changes in motor planning abilities with age, and factors underlying these changes.

End-State Comfort Across the Lifespan: A Cross-Sectional Investigation of How Movement Context Influences Motor Planning in an Overturned Glass Task

Young adults plan actions in advance to minimize the cost of movement. This is exemplified by the end-state comfort (ESC) effect. A pattern of improvement in ESC in children is linked to the development of cognitive control processes, and decline in older adults is attributed to cognitive decline. This study used a cross-sectional design to examine how movement context (pantomime, demonstration with image/glass as a guide, actual grasping) influences between-hand differences in ESC planning. Children (5- to 12-year-olds), young adults, and two groups of older adults (aged 60-70, and aged 71 and older) were assessed. Findings provide evidence for adult-like patterns of ESC in 8-year-olds. Results are attributed to improvements in proprioceptive acuity and proficiency in generating and implementing internal representations of action. For older adults early in the aging process, sensitivity to ESC did not differ from young adults. However, with increasing age, differences reflect challenges in motor planning with increases in cognitive demand, similar to previous work. Findings have implications for understanding lifespan motor behavior.

Decisions in motion: passive body acceleration modulates hand choice

In everyday life, we frequently have to decide which hand to use for a certain action. It has been suggested that for this decision the brain calculates expected costs based on action values, such as expected biomechanical costs, expected success rate, handedness, and skillfulness. Although these conclusions were based on experiments in stationary subjects, we often act while the body is in motion. We investigated how hand choice is affected by passive body motion, which directly affects the biomechanical costs of the arm movement due to its inertia. With the use of a linear motion platform, 12 right-handed subjects were sinusoidally translated (0.625 and 0.5 Hz). At 8 possible motion phases, they had to reach, using either their left or right hand, to a target presented at 1 of 11 possible locations. We predicted hand choice by calculating the expected biomechanical costs under different assumptions about the future acceleration involved in these computations, being the forthcoming acceleration during the reach, the instantaneous acceleration at target onset, or zero acceleration as if the body were stationary. Although hand choice was generally biased to use of the dominant hand, it also modulated sinusoidally with the motion, with the amplitude of the bias depending on the motion's peak acceleration. The phase of hand choice modulation was consistent with the cost model that took the instantaneous acceleration signal at target onset. This suggests that the brain relies on the bottom-up acceleration signals, and not on predictions about future accelerations, when deciding on hand choice during passive whole body motion.NEW & NOTEWORTHY Decisions of hand choice are a fundamental aspect of human behavior. Whereas these decisions are typically studied in stationary subjects, this study examines hand choice while subjects are in motion. We show that accelerations of the body, which differentially modulate the biomechanical costs of left and right hand movements, are also taken into account when deciding which hand to use for a reach, possibly based on bottom-up processing of the otolith signal.