The Brain in Action Laboratory, Department of Kinesiology, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada.
Exp Brain Res. 2022 Jan;240(1):135-145. doi: 10.1007/s00221-021-06241-2. Epub 2021 Oct 15.
We rely on accurate body representations to successfully interact with the environment. As adults, we rely on many years of experience with a body that has stayed relatively the same size. Children, however, go through periods of rapid growth and whether or not their body representation matches this physical growth is unknown. To address this question, we examined the developmental trajectory of the body model of the hand. The body model is the representation of our bodies that underlies position sense. We recruited a group of children (8-16 years) and a control group of young adults (18-26 years) and asked them to complete the body model task. In this task, participants estimated the location of ten different landmarks (the tips and metacarpophalangeal joints of each of their five fingers). The position (XY location) of each estimate was tracked using an Optotrak camera. From the XY locations we derived hand width and finger length. Not surprisingly, children's physical hand width and finger length were smaller than adults but remarkably, the body model, was similar for both groups. This result indicates that children overestimate hand size and suggests that the body model is ahead of physical growth. This result contradicts the notion that body representation lags physical growth during puberty, accounting for the clumsy motor behaviour characteristic of teens. We discuss the results in relation to the different taxonomies of body representation and how an enlarged representation of the hand during childhood may influence action.
我们依靠准确的身体表象来成功地与环境互动。作为成年人，我们依靠多年来与相对保持不变大小的身体的经验。然而，儿童经历了快速生长的时期，他们的身体表象是否与这种身体生长相匹配尚不清楚。为了解决这个问题，我们研究了手部身体模型的发展轨迹。身体模型是我们身体的表象，是位置感的基础。我们招募了一组儿童（8-16 岁）和一组年轻成年人（18-26 岁）对照组，并要求他们完成身体模型任务。在这个任务中，参与者估计了十个不同地标（他们五个手指的指尖和掌指关节）的位置。使用 Optotrak 摄像机跟踪每个估计的位置（XY 位置）。从 XY 位置我们得出了手宽和手指长度。不出所料，儿童的实际手宽和手指长度小于成年人，但令人惊讶的是，两组的身体模型相似。这一结果表明，儿童高估了手的大小，这表明身体模型领先于身体生长。这一结果与青春期身体表象滞后于身体生长的观点相矛盾，解释了青少年特有的笨拙运动行为。我们讨论了这些结果与身体表象的不同分类以及儿童时期手部表象的扩大如何影响动作的关系。
