Li Min Susan, Abbatecola Clement, Petro Lucy S, Muckli Lars
Centre for Cognitive Neuroimaging, School of Psychology and Neuroscience, University of Glasgow, Glasgow, United Kingdom.
Front Hum Neurosci. 2021 Nov 3;15:750417. doi: 10.3389/fnhum.2021.750417. eCollection 2021.
Peripheral vision has different functional priorities for mammals than foveal vision. One of its roles is to monitor the environment while central vision is focused on the current task. Becoming distracted too easily would be counterproductive in this perspective, so the brain should react to behaviourally relevant changes. Gist processing is good for this purpose, and it is therefore not surprising that evidence from both functional brain imaging and behavioural research suggests a tendency to generalize and blend information in the periphery. This may be caused by the balance of perceptual influence in the periphery between bottom-up (i.e., sensory information) and top-down (i.e., prior or contextual information) processing channels. Here, we investigated this interaction behaviourally using a peripheral numerosity discrimination task with top-down and bottom-up manipulations. Participants compared numerosity between the left and right peripheries of a screen. Each periphery was divided into a centre and a surrounding area, only one of which was a task relevant target region. Our top-down task modulation was the instruction which area to attend - centre or surround. We varied the signal strength by altering the stimuli durations i.e., the amount of information presented/processed (as a combined bottom-up and recurrent top-down feedback factor). We found that numerosity perceived in target regions was affected by contextual information in neighbouring (but irrelevant) areas. This effect appeared as soon as stimulus duration allowed the task to be reliably performed and persisted even at the longest duration (1 s). We compared the pattern of results with an ideal-observer model and found a qualitative difference in the way centre and surround areas interacted perceptually in the periphery. When participants reported on the central area, the irrelevant surround would affect the response as a weighted combination - consistent with the idea of a receptive field focused in the target area to which irrelevant surround stimulation leaks in. When participants report on surround, we can best describe the response with a model in which occasionally the attention switches from task relevant surround to task irrelevant centre - consistent with a selection model of two competing streams of information. Overall our results show that the influence of spatial context in the periphery is mandatory but task dependent.
与中央凹视觉相比，周边视觉对哺乳动物具有不同的功能优先级。其作用之一是在中央视觉专注于当前任务时监控环境。从这个角度来看，过于容易分心会适得其反，因此大脑应该对行为相关的变化做出反应。要点处理适合此目的，因此功能性脑成像和行为研究的证据表明在外围存在概括和融合信息的倾向也就不足为奇了。这可能是由自下而上（即感觉信息）和自上而下（即先验或上下文信息）处理通道在外围的感知影响平衡所导致的。在此，我们使用具有自上而下和自下而上操作的周边数字辨别任务，从行为学角度研究了这种相互作用。参与者比较屏幕左右周边的数字。每个周边被分为一个中心区域和一个周围区域，其中只有一个是与任务相关的目标区域。我们的自上而下任务调制是指示要关注的区域——中心区域还是周围区域。我们通过改变刺激持续时间来改变信号强度，即呈现/处理的信息量（作为自下而上和循环自上而下反馈因素的组合）。我们发现目标区域中感知到的数字受到相邻（但不相关）区域中的上下文信息影响。这种效应在刺激持续时间允许可靠执行任务时就会出现，并且即使在最长持续时间（1秒）时也会持续存在。我们将结果模式与理想观察者模型进行了比较，发现在周边区域中心区域和周围区域在感知上相互作用的方式存在质的差异。当参与者报告中心区域时，不相关的周围区域会作为加权组合影响反应——这与聚焦在目标区域的感受野概念一致，不相关的周围刺激会泄漏到该感受野中。当参与者报告周围区域时，我们可以用一个模型最好地描述反应，在该模型中，注意力偶尔会从与任务相关的周围区域切换到与任务无关的中心区域——这与两个竞争信息流的选择模型一致。总体而言，我们的结果表明周边空间上下文的影响是强制性的，但依赖于任务。
