University of Trento.
J Cogn Neurosci. 2013 May;25(5):697-705. doi: 10.1162/jocn_a_00349. Epub 2012 Dec 18.
Exact computation of numerosity requires the selective individuation of the elements to be enumerated so that each element is counted once and only once. Such a mechanism should operate not only when the elements to be enumerated are presented in isolation but also when they are presented in cluttered scenes. To uncover the electrophysiological correlates of the level of object representation necessary for exact enumeration, we examined ERP measures during the execution of a target enumeration task. A variable number (1-4) of lateralized targets were presented with or without distracters on the target side. An early nonlateralized response (N1, 120-180 msec) was modulated by target numerosity only when presented without distracters. By contrast, the amplitudes of a lateralized and later response (N2pc, 180-300 msec) increased as a function of target numerosity both with and without distracters, reaching a plateau at three targets. We propose that the stage of processing reflected in the N2pc corresponds to the component of individuation that binds specific indexes to properties and locations and that this provides the representation type necessary for exact enumeration.
精确计算数量需要选择性地对要计数的元素进行个体识别，以使每个元素被计数一次且仅计数一次。这种机制不仅应该在要计数的元素单独呈现时起作用，而且应该在它们在杂乱场景中呈现时起作用。为了揭示精确计数所需的对象表示水平的电生理相关性，我们在执行目标计数任务期间检查了 ERP 测量。在没有分心物的情况下，以侧化的方式呈现 1-4 个变量数量的目标。只有在没有分心物的情况下，早期的非侧化反应（N1，120-180ms）才会受到目标数量的调制。相比之下，侧化和后来的反应（N2pc，180-300ms）的幅度随着目标数量的增加而增加，无论是有分心物还是没有分心物，在三个目标时达到平台。我们提出，N2pc 所反映的处理阶段对应于将特定索引绑定到属性和位置的个体化组件，并且这提供了用于精确计数的表示类型。
