Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
Faculty of Psychology, Education and Sport Science, Institute of Psychology, University of Regensburg, Germany; Centre For Mind/Brain Sciences (CIMeC), University of Trento, Italy.
Neuropsychologia. 2020 Dec;149:107673. doi: 10.1016/j.neuropsychologia.2020.107673. Epub 2020 Nov 10.
The general aim of this study was to assess the effect produced by visuo-spatial attention on both behavioural performance and brain activation in hemianopic patients following visual stimulus presentation to the blind hemifield. To do that, we tested five hemianopic patients and six age-matched healthy controls in an MRI scanner during the execution of a Posner-like paradigm using a predictive central cue. Participants were instructed to covertly orient attention toward the blind or sighted hemifield in different blocks while discriminating the orientation of a visual grating. In patients, we found significantly faster reaction times (RT) in valid and neutral than invalid trials not only in the sighted but also in the blind hemifield, despite the impairment of consciousness and performance at chance. As to the fMRI signal, in valid trials we observed the activation of ipsilesional visual areas (mainly lingual gyrus - area 19) during the orientation of attention toward the blind hemifield. Importantly, this activation was similar in patients and controls. In order to assess the related functional network, we performed a psychophysiological interactions (PPI) analysis that revealed an increased functional connectivity (FC) in patients with respect to controls between the ipsilesional lingual gyrus and ipsilateral fronto-parietal as well as contralesional parietal regions. Moreover, the shift of attention from the blind to the sighted hemifield revealed stronger FC between the contralesional visual areas V3/V4 and ipsilateral parietal regions in patients than controls. These results indicate a higher cognitive effort in patients when paying attention to the blind hemifiled or when shifting attention from the blind to the sighted hemfield, possibly as an attempt to compensate for the visual loss. Taken together, these results show that hemianopic patients can covertly orient attention toward the blind hemifield with a top-down mechanism by activating a functional network mainly including fronto-parietal regions belonging to the dorsal attentional network.
本研究的总体目的是评估在向盲视野呈现视觉刺激后，视空间注意对偏盲患者的行为表现和大脑激活的影响。为此，我们在 MRI 扫描仪中对五名偏盲患者和六名年龄匹配的健康对照者进行了测试，在执行类似于 Posner 的范式时使用预测性中央线索。参与者被指示在不同的块中，当辨别视觉光栅的方向时，将注意力隐蔽地转向盲视或视力视野。在患者中，我们发现不仅在视力视野中，而且在盲视野中，与无效试验相比，有效和中性试验的反应时间（RT）明显更快，尽管意识和表现都低于机会水平。至于 fMRI 信号，在有效试验中，我们观察到在将注意力转向盲视野时，同侧视觉区域（主要是舌回 - 区域 19）的激活。重要的是，这种激活在患者和对照组中是相似的。为了评估相关的功能网络，我们进行了心理生理相互作用（PPI）分析，结果表明患者相对于对照组，同侧舌回与同侧额顶叶以及对侧顶叶区域之间的功能连接（FC）增加。此外，当注意力从盲视野转移到视力视野时，患者的对侧视觉区域 V3/V4 和同侧顶叶区域之间的 FC 比对照组更强。这些结果表明，当患者注意盲视野或从盲视野转移到视力视野时，他们会付出更高的认知努力，这可能是试图补偿视力丧失。总之，这些结果表明，偏盲患者可以通过激活主要包括属于背侧注意网络的额顶叶区域的自上而下机制，将注意力隐蔽地转向盲视野。
