Bosco Annalisa, Piserchia Valentina, Fattori Patrizia
Department of Pharmacy and Biotechnology, University of BolognaBologna, Italy.
Front Hum Neurosci. 2017 Jun 23;11:323. doi: 10.3389/fnhum.2017.00323. eCollection 2017.
Reaching behavior represents one of the basic aspects of human cognitive abilities important for the interaction with the environment. Reaching movements towards visual objects are controlled by mechanisms based on coordinate systems that transform the spatial information of target location into appropriate motor response. Although recent works have extensively studied the encoding of target position for reaching in three-dimensional space at behavioral level, the combined analysis of reach errors and movement variability has so far been investigated by few studies. Here we did so by testing 12 healthy participants in an experiment where reaching targets were presented at different depths and directions in foveal and peripheral viewing conditions. Each participant executed a memory-guided task in which he/she had to reach the memorized position of the target. A combination of vector and gradient analysis, novel for behavioral data, was applied to analyze patterns of reach errors for different combinations of eye/target positions. The results showed reach error patterns based on both eye- and space-centered coordinate systems: in depth more biased towards a space-centered representation and in direction mixed between space- and eye-centered representation. We calculated movement variability to describe different trajectory strategies adopted by participants while reaching to the different eye/target configurations tested. In direction, the distribution of variability between configurations that shared the same eye/target relative configuration was different, whereas in configurations that shared the same spatial position of targets, it was similar. In depth, the variability showed more similar distributions in both pairs of eye/target configurations tested. These results suggest that reaching movements executed in geometries that require hand and eye dissociations in direction and depth showed multiple coordinate systems and different trajectory strategies according to eye/target configurations and the two dimensions of space.
伸手行为是人类认知能力的基本方面之一，对与环境的交互很重要。朝向视觉物体的伸手动作由基于坐标系的机制控制，该坐标系将目标位置的空间信息转换为适当的运动反应。尽管最近的研究在行为层面广泛研究了在三维空间中伸手时目标位置的编码，但到目前为止，很少有研究对伸手误差和运动变异性进行综合分析。在这里，我们通过在一项实验中测试12名健康参与者来进行综合分析，在该实验中，在中央凹和周边视觉条件下，伸手目标在不同深度和方向呈现。每个参与者执行一项记忆引导任务，其中他/她必须到达目标的记忆位置。一种结合向量和梯度分析的方法（这对行为数据来说是新颖的）被应用于分析不同眼/目标位置组合的伸手误差模式。结果显示了基于以眼睛为中心和以空间为中心的坐标系的伸手误差模式：在深度上更偏向以空间为中心的表示，在方向上则在以空间为中心和以眼睛为中心的表示之间混合。我们计算了运动变异性，以描述参与者在伸手到测试的不同眼/目标配置时采用的不同轨迹策略。在方向上，共享相同眼/目标相对配置的配置之间的变异性分布不同，而在共享相同目标空间位置的配置中，变异性分布相似。在深度上，在测试的两对眼/目标配置中，变异性显示出更相似的分布。这些结果表明，在需要手和眼在方向和深度上分离的几何结构中执行的伸手动作，根据眼/目标配置和空间的两个维度，显示出多个坐标系和不同的轨迹策略。
