Development of reaching during mid-childhood from a Developmental Systems perspective.

Laura Golenia,Marina M Schoemaker,Leonora J Mouton,Raoul M Bongers,Egbert Otten,Gavin Buckingham

doi:10.1371/journal.pone.0193463

Laura Golenia, Marina M Schoemaker + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0193463

Copy DOI

Abstract

Inspired by the Developmental Systems perspective, we studied the development of reaching during mid-childhood (5–10 years of age) not just at the performance level (i.e., endpoint movements), as commonly done in earlier studies, but also at the joint angle level. Because the endpoint position (i.e., the tip of the index finger) at the reaching target can be achieved with multiple joint angle combinations, we partitioned variability in joint angles over trials into variability that does not (goal-equivalent variability, GEV) and that does (non-goal-equivalent variability, NGEV) influence the endpoint position, using the Uncontrolled Manifold method. Quantifying this structure in joint angle variability allowed us to examine whether and how spatial variability of the endpoint at the reaching target is related to variability in joint angles and how this changes over development. 6-, 8- and 10-year-old children and young adults performed reaching movements to a target with the index finger. Polynomial trend analysis revealed a linear and a quadratic decreasing trend for the variable error. Linear decreasing and cubic trends were found for joint angle standard deviations at movement end. GEV and NGEV decreased gradually with age, but interestingly, the decrease of GEV was steeper than the decrease of NGEV, showing that the different parts of the joint angle variability changed differently over age. We interpreted these changes in the structure of variability as indicating changes over age in exploration for synergies (a family of task solutions), a concept that links the performance level with the joint angle level. Our results suggest changes in the search for synergies during mid-childhood development.

Highlights

The development of goal-directed reaching is important as reaching is involved in many manual everyday life actions
Inspired by the Developmental Systems (DS) approach, we studied developmental trends not just at the performance level, as commonly done in earlier studies, and at joint angle level
Our results showed different statistical contrasts significant at different levels, which implies different developmental trends at each level, indicating the importance of focusing on different levels for achieving understanding of reaching development

Summary

Introduction

The development of goal-directed reaching is important as reaching is involved in many manual everyday life actions. Development of reaching during mid-childhood movements become more accurate and less variable with increasing age [1,2,3,4] and that reaching movements can be better adjusted to sudden changes in target location [5,6,7,8,9] Doing so, these studies did not emphasize the contribution and development of other levels of analysis involved in reaching, such as for instance the joint level (see for an exception Schneiberg et al [10]). These studies did not emphasize the contribution and development of other levels of analysis involved in reaching, such as for instance the joint level (see for an exception Schneiberg et al [10]) This might be attributed to the theoretical approach underlying these studies, such as the information processing approach or the computational neuroscience perspective (i.e., internal models and representations). Even though these studies and approaches have gathered important knowledge about mid-childhood development, we propose that if one wants to understand the full range and complexity of developmental changes, one should depart from studying just one level and should distinguish the development of individual levels contributing to reaching (see for detail criticism of earlier studies Golenia et al [14])

Objectives

Methods

Results

Conclusion