Striemer Christopher L, Borza Carley A
Department of Psychology, MacEwan University, 10700-104 Avenue, Edmonton, AB, T5J 4S2, Canada.
Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.
Exp Brain Res. 2017 Oct;235(10):3193-3206. doi: 10.1007/s00221-017-5038-9. Epub 2017 Jul 28.
Damage to the temporal-parietal cortex in the right hemisphere often leads to spatial neglect-a disorder in which patients are unable to attend to sensory input from their contralesional (left) side. Neglect has been associated with both attentional and premotor deficits. That is, in addition to having difficulty with attending to the left side, patients are often slower to initiate leftward vs. rightward movements (i.e., directional hypokinesia). Previous research has indicated that a brief period of adaptation to rightward shifting prisms can reduce symptoms of neglect by adjusting the patient's movements leftward, toward the neglected field. Although prism adaptation has been shown to reduce spatial attention deficits in patients with neglect, very little work has examined the effects of prisms on premotor symptoms. In the current study, we examined this in healthy individuals using leftward shifting prisms to induce a rightward shift in the egocentric reference frame, similar to neglect patients prior to prism adaptation. Specifically, we examined the speed with which healthy participants initiated leftward and rightward reaches (without visual feedback) prior to and following adaptation to either 17° leftward (n = 16) or 17° rightward (n = 15) shifting prisms. Our results indicated that, following adaptation, participants were significantly faster to initiate reaches towards targets located in the direction opposite the prism shift. That is, participants were faster to initiate reaches to right targets following leftward prism adaptation and were faster to initiate reaches to left targets following rightward prism adaptation. Overall, these results are consistent with the idea that prism adaptation can influence the speed with which a reach can be initiated toward a target in the direction opposite the prism shift, possibly through altering activity in neural circuits involved in reach planning.
右半球颞顶叶皮质受损通常会导致空间忽视——一种患者无法注意到来自对侧（左侧）感觉输入的病症。忽视与注意力和运动前区缺陷都有关联。也就是说，除了难以注意左侧外，患者向左与向右运动的启动通常更慢（即方向运动减退）。先前的研究表明，短暂适应向右偏移的棱镜可以通过将患者的运动向左调整至被忽视区域来减轻忽视症状。尽管棱镜适应已被证明可减少忽视患者的空间注意力缺陷，但很少有研究探讨棱镜对运动前区症状的影响。在本研究中，我们在健康个体中进行了此项研究，使用向左偏移的棱镜在自我中心参照系中诱发向右偏移，类似于棱镜适应前的忽视患者。具体而言，我们考察了健康参与者在适应17°向左（n = 16）或17°向右（n = 15）偏移棱镜之前和之后（无视觉反馈）启动向左和向右伸手动作的速度。我们的结果表明，适应后，参与者启动向与棱镜偏移方向相反的目标伸手动作的速度显著加快。也就是说，向左棱镜适应后参与者启动向右侧目标伸手动作更快，向右棱镜适应后参与者启动向左侧目标伸手动作更快。总体而言，这些结果与以下观点一致，即棱镜适应可能通过改变参与伸手动作规划的神经回路活动，来影响向与棱镜偏移方向相反的目标伸手动作的启动速度。
