Visual Neuroscience Laboratory, IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
Neuropsychologia. 2013 Sep;51(11):2120-9. doi: 10.1016/j.neuropsychologia.2013.07.007. Epub 2013 Jul 17.
In human cognition, most relevant stimuli, such as faces, are processed in central vision. However, it is widely believed that recognition of relevant stimuli (e.g. threatening animal faces) at peripheral locations is also important due to their survival value. Moreover, task instructions have been shown to modulate brain regions involved in threat recognition (e.g. the amygdala). In this respect it is also controversial whether tasks requiring explicit focus on stimulus threat content vs. implicit processing differently engage primitive subcortical structures involved in emotional appraisal. Here we have addressed the role of central vs. peripheral processing in the human amygdala using animal threatening vs. non-threatening face stimuli. First, a simple animal face recognition task with threatening and non-threatening animal faces, as well as non-face control stimuli, was employed in naïve subjects (implicit task). A subsequent task was then performed with the same stimulus categories (but different stimuli) in which subjects were told to explicitly detect threat signals. We found lateralized amygdala responses both to the spatial location of stimuli and to the threatening content of faces depending on the task performed: the right amygdala showed increased responses to central compared to left presented stimuli specifically during the threat detection task, while the left amygdala was better prone to discriminate threatening faces from non-facial displays during the animal face recognition task. Additionally, the right amygdala responded to faces during the threat detection task but only when centrally presented. Moreover, we have found no evidence for superior responses of the amygdala to peripheral stimuli. Importantly, we have found that striatal regions activate differentially depending on peripheral vs. central processing of threatening faces. Accordingly, peripheral processing of these stimuli activated more strongly the putaminal region, while central processing engaged mainly the caudate nucleus. We conclude that the human amygdala has a central bias for face stimuli, and that visual processing recruits different striatal regions, putaminal or caudate based, depending on the task and on whether peripheral or central visual processing is involved.
在人类认知中，大多数相关刺激，如面部，都在中央视觉中进行处理。然而，人们普遍认为，由于相关刺激（例如威胁性动物面孔）的生存价值，在周边位置识别这些刺激也很重要。此外，任务指令已被证明可以调节参与威胁识别的大脑区域（例如杏仁核）。在这方面，还存在争议的是，需要明确关注刺激威胁内容的任务与隐含处理是否会以不同的方式使参与情感评估的原始皮质下结构参与进来。在这里，我们使用动物威胁性与非威胁性面孔刺激来研究中央与周边处理在人类杏仁核中的作用。首先，在未经训练的受试者中使用具有威胁性和非威胁性动物面孔以及非面孔控制刺激的简单动物面孔识别任务（隐含任务）。然后，使用相同的刺激类别（但使用不同的刺激）执行后续任务，其中告知受试者明确检测威胁信号。我们发现，杏仁核的反应与刺激的空间位置和面孔的威胁内容有关，这取决于所执行的任务：在威胁检测任务中，与左呈现的刺激相比，右侧杏仁核对中央呈现的刺激的反应增加，而在动物面孔识别任务中，左侧杏仁核更倾向于将威胁性面孔与非面部显示区分开来。此外，在威胁检测任务中，右侧杏仁核对面孔有反应，但仅在中央呈现时才会有反应。此外，我们没有发现杏仁核对周边刺激有更好反应的证据。重要的是，我们发现，纹状体区域的反应根据威胁性面孔的周边或中央处理而有所不同。因此，这些刺激的周边处理更强烈地激活了壳核区域，而中央处理则主要涉及尾状核。我们得出结论，人类杏仁核对面部刺激具有中央偏向性，并且视觉处理根据任务以及是否涉及周边或中央视觉处理，会激活不同的纹状体区域，即壳核或尾状核。
