Jefferies International Limited , London, UK.
Department of Neurobiology, Stanford University School of Medicine , Stanford, CA, USA ; Howard Hughes Medical Institute , Stanford, CA, USA.
Front Psychol. 2015 Mar 2;6:155. doi: 10.3389/fpsyg.2015.00155. eCollection 2015.
In order to deal with a large amount of information carried by visual inputs entering the brain at any given point in time, the brain swiftly uses the same inputs to enhance processing in one part of visual field at the expense of the others. These processes, collectively called bottom-up attentional selection, are assumed to solely rely on feedforward processing of the external inputs, as it is implied by the nomenclature. Nevertheless, evidence from recent experimental and modeling studies points to the role of feedback in bottom-up attention. Here, we review behavioral and neural evidence that feedback inputs are important for the formation of signals that could guide attentional selection based on exogenous inputs. Moreover, we review results from a modeling study elucidating mechanisms underlying the emergence of these signals in successive layers of neural populations and how they depend on feedback from higher visual areas. We use these results to interpret and discuss more recent findings that can further unravel feedforward and feedback neural mechanisms underlying bottom-up attention. We argue that while it is descriptively useful to separate feedforward and feedback processes underlying bottom-up attention, these processes cannot be mechanistically separated into two successive stages as they occur at almost the same time and affect neural activity within the same brain areas using similar neural mechanisms. Therefore, understanding the interaction and integration of feedforward and feedback inputs is crucial for better understanding of bottom-up attention.
为了处理在任何特定时刻进入大脑的大量视觉输入所携带的信息,大脑会迅速利用相同的输入来增强视野中某一部分的处理,而牺牲其他部分。这些过程统称为自下而上的注意选择,据其名称可知,它们被认为仅依赖于外部输入的前馈处理。然而,最近的实验和建模研究的证据表明,反馈在自下而上的注意中起着作用。在这里,我们回顾了行为和神经证据,表明反馈输入对于形成可以根据外部输入引导注意选择的信号很重要。此外,我们回顾了一项建模研究的结果,该研究阐明了在神经群体的连续层中出现这些信号的机制,以及它们如何依赖于来自更高视觉区域的反馈。我们使用这些结果来解释和讨论最近的发现,这些发现可以进一步揭示自下而上注意的前馈和反馈神经机制。我们认为,虽然将自下而上注意的前馈和反馈过程分开进行描述在描述上是有用的,但这些过程不能在机制上分为两个连续的阶段,因为它们几乎同时发生,并使用类似的神经机制影响同一大脑区域的神经活动。因此,理解前馈和反馈输入的相互作用和整合对于更好地理解自下而上的注意至关重要。