The School of Psychology University of East Anglia Norwich, NR4 7TJ UK.
Cortex. 2013 Oct;49(9):2525-41. doi: 10.1016/j.cortex.2012.12.014. Epub 2013 Jan 8.
Humans are more efficient when performing actions towards objects presented in the lower visual field (VF) than in the upper VF. The present study used slow event-related functional magnetic resonance imaging (fMRI) to examine whether human brain areas implicated in action would show such VF preferences. Participants were asked to fixate one of four different positions allowing objects to be presented in the upper left, upper right, lower left or lower right VF. In some trials they reached to grasp the object with the right hand while in others they passively viewed the object. Crucially, by manipulating the fixation position, rather than the position of the objects, the biomechanics of the movements did not differ across conditions. The superior parieto-occipital cortex (SPOC) and the left precuneus, brain areas implicated in the control of reaching, were significantly more activated when participants grasped objects presented in the lower VF relative to the upper VF. Importantly, no such VF preferences were observed in these regions during passive viewing. This finding fits well with evidence from the macaque neurophysiology that neurons within visuomotor regions over-represent the lower VF relative to the upper VF and indicate that the neural responses within these regions may reflect a functional lower VF advantage during visually-guided actions.
当人们对呈现在下视野 (VF) 中的物体执行动作时，比呈现在上 VF 中的物体更有效率。本研究使用慢事件相关功能磁共振成像 (fMRI) 来检查涉及动作的人脑区域是否会表现出这种 VF 偏好。参与者被要求注视四个不同位置中的一个，允许物体呈现在左上方、右上方、左下方或右下方的 VF 中。在一些试验中，他们用右手伸手去抓物体，而在另一些试验中，他们被动地观察物体。至关重要的是，通过操纵注视位置而不是物体的位置，运动的生物力学在不同条件下没有差异。上顶叶枕区 (SPOC) 和左侧楔前叶，与伸手控制有关的大脑区域，当参与者抓取呈现在下 VF 中的物体时，比呈现在上 VF 中的物体明显更活跃。重要的是，在被动观察期间，这些区域没有观察到这种 VF 偏好。这一发现与猕猴神经生理学的证据非常吻合，即视觉运动区域内的神经元对上 VF 的代表性过高，而下 VF 的代表性过低，这表明这些区域内的神经反应可能反映了在视觉引导动作期间下 VF 的功能优势。
