Fondazione Santa Lucia IRCCS, Roma, Italy.
Dipartimento di Psicologia, Università degli Studi di Roma 'La Sapienza', Roma, Italy; Fondazione Santa Lucia IRCCS, Roma, Italy.
Neuropsychologia. 2021 Apr 16;154:107773. doi: 10.1016/j.neuropsychologia.2021.107773. Epub 2021 Feb 7.
Whether the semantic representation of numbers is endowed with an intrinsic spatial component, so that smaller numbers are inherently represented to the left of larger ones on a Mental Number Line (MNL), is a central matter of debate in numerical cognition. To gain an insight into this issue, we investigated the performance of right brain damaged patients with left spatial neglect (N+) in a bimanual Magnitude Comparison SNARC task and in a uni-manual Magnitude Comparison Go/No-Go task (i.e. "is the number smaller or larger than 5?"). While the first task requires the use of contrasting left/right spatial codes for response selection, the second task does not require the use of these codes. In line with previous evidence, in the SNARC task N+ patients displayed a significant asymmetry in Reaction Times (RTs), with slower RTs to number "4", that was immediately precedent to the numerical reference "5", with respect to the number "6", that immediately followed the same reference. This RTs asymmetry was correlated with lesion of white matter tracts, i.e. Fronto-Occipital-Fasciculus, that allows prefrontal Ba 8 and 46 to regulate the distribution of attention on sensory and memory traces in posterior occipital, temporal and parietal areas. In contrast, no similar RTs asymmetry was found in the Go/No-Go task. These findings suggest that while in the SNARC task numbers get mentally organised from left-to-right as a function of their increasing magnitude, so that N+ patients display a delay in the processing of number-magnitudes that are immediately smaller than a given numerical reference, in the Go/No-Go task no left-to-right organization is activated. These results support the idea that it is the use of contrasting left/right spatial codes, whether motor or conceptual, that triggers the generation of a spatially left-to-right organised MNL and that the representation of number magnitude is not endowed with an inherent spatial component.
数字的语义表示是否具有内在的空间成分，使得较小的数字在心理数字线上（MNL）上固有地位于较大的数字的左侧，这是数值认知中争论的核心问题。为了深入了解这个问题，我们研究了患有左空间忽视（N+）的右脑损伤患者在双手 Magnitude Comparison SNARC 任务和单手 Magnitude Comparison Go/No-Go 任务（即“数字是小于还是大于 5？”）中的表现。虽然第一项任务要求使用对比的左/右空间代码进行响应选择，但第二项任务不需要使用这些代码。与之前的证据一致，在 SNARC 任务中，N+ 患者的反应时间（RT）表现出明显的不对称性，与紧随同一参考数字“5”的数字“6”相比，数字“4”的 RT 较慢，该参考数字立即在其之前。这种 RT 不对称性与白质束，即额枕束的损伤相关，该束允许前额叶 Ba8 和 46 调节注意力在后部枕叶、颞叶和顶叶区域的感觉和记忆痕迹上的分布。相比之下，在 Go/No-Go 任务中没有发现类似的 RT 不对称性。这些发现表明，虽然在 SNARC 任务中，数字会根据其递增的大小从左到右进行心理组织，因此 N+ 患者在处理立即小于给定数字参考的数字-数量时会出现延迟，但在 Go/No-Go 任务中不会激活从左到右的组织。这些结果支持这样的观点，即使用对比的左/右空间代码（无论是运动还是概念）会触发生成一个从左到右组织的 MNL，并且数字大小的表示没有内在的空间成分。
