Martuzzi Roberto, Murray Micah M, Maeder Philippe P, Fornari Eleonora, Thiran Jean- Philippe, Clarke Stephanie, Michel Christoph M, Meuli Reto A
Service de Radiodiagnostic et Radiologie Interventionnelle, Center Hospitalier Universitaire Vaudois, rue du Bugnon 46, Lausanne, Switzerland.
Exp Brain Res. 2006 Apr;170(4):472-87. doi: 10.1007/s00221-005-0232-6. Epub 2005 Nov 24.
Whether different brain networks are involved in generating unimanual responses to a simple visual stimulus presented in the ipsilateral versus contralateral hemifield remains a controversial issue. Visuo-motor routing was investigated with event-related functional magnetic resonance imaging (fMRI) using the Poffenberger reaction time task. A 2 hemifield x 2 response hand design generated the "crossed" and "uncrossed" conditions, describing the spatial relation between these factors. Both conditions, with responses executed by the left or right hand, showed a similar spatial pattern of activated areas, including striate and extrastriate areas bilaterally, SMA, and M1 contralateral to the responding hand. These results demonstrated that visual information is processed bilaterally in striate and extrastriate visual areas, even in the "uncrossed" condition. Additional analyses based on sorting data according to subjects' reaction times revealed differential crossed versus uncrossed activity only for the slowest trials, with response strength in infero-temporal cortices significantly correlating with crossed-uncrossed differences (CUD) in reaction times. Collectively, the data favor a parallel, distributed model of brain activation. The presence of interhemispheric interactions and its consequent bilateral activity is not determined by the crossed anatomic projections of the primary visual and motor pathways. Distinct visuo-motor networks need not be engaged to mediate behavioral responses for the crossed visual field/response hand condition. While anatomical connectivity heavily influences the spatial pattern of activated visuo-motor pathways, behavioral and functional parameters appear to also affect the strength and dynamics of responses within these pathways.
不同的脑网络是否参与对同侧与对侧半视野中呈现的简单视觉刺激产生单手反应，仍然是一个有争议的问题。使用事件相关功能磁共振成像（fMRI）和波芬伯格反应时任务研究了视觉运动通路。一个2半视野×2反应手的设计产生了“交叉”和“不交叉”条件，描述了这些因素之间的空间关系。两种条件下，无论用左手还是右手执行反应，激活区域的空间模式都相似，包括双侧的纹状和纹外区域、辅助运动区（SMA）以及与反应手对侧的初级运动皮层（M1）。这些结果表明，即使在“不交叉”条件下，视觉信息在纹状和纹外视觉区域也是双侧处理的。根据受试者反应时间对数据进行分类的进一步分析显示，仅在最慢的试验中交叉与不交叉活动存在差异，颞下皮层的反应强度与反应时间的交叉-不交叉差异（CUD）显著相关。总体而言，这些数据支持一种平行、分布式的脑激活模型。半球间相互作用的存在及其导致的双侧活动并非由初级视觉和运动通路的交叉解剖投射决定。对于交叉视野/反应手条件，不需要不同的视觉运动网络来介导行为反应。虽然解剖连接性严重影响激活的视觉运动通路的空间模式，但行为和功能参数似乎也会影响这些通路内反应的强度和动态。
