Roxelyn & Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, USA.
Mesulam Cognitive Neurology and Alzheimer's Disease Center, Northwestern University, USA; Ken & Ruth Davee Department of Neurology, Northwestern University, USA.
Neuropsychologia. 2019 Nov;134:107192. doi: 10.1016/j.neuropsychologia.2019.107192. Epub 2019 Sep 13.
Impaired sentence comprehension is observed in the three major subtypes of PPA, with distinct performance patterns relating to impairments in comprehending complex sentences in the agrammatic (PPA-G) and logopenic (PPA-L) variants and word comprehension in the semantic subtype (PPA-S). However, little is known about basic combinatory processes during sentence comprehension in PPA, such the integration of verbs with their subject and object(s) (verb-argument integration).
The present study used visual-world eye-tracking to examine real-time verb-argument integration in individuals with PPA (12 with PPA-G, 10 with PPA-L, and 6 with PPA-S) and neurotypical older adults (15). Two baseline experiments probed eye movement control, using a non-linguistic task, and noun comprehension, respectively. Two verb-argument integration experiments examined the effects of verb meaning on (a) lexical access of the verb's direct object (argument access) and (b) selection of a semantically-appropriate direct object (argument selection), respectively. Eye movement analyses were conducted only for trials with correct behavioral responses, allowing us to distinguish accuracy and online processing.
The eye movement control experiment revealed no significant impairments in PPA, whereas the noun comprehension experiment revealed reduced accuracy and eye-movement latencies in PPA-S, and to a lesser extent PPA-G. In the argument access experiment, verb meaning facilitated argument access normally in PPA-G and PPA-L; in PPA-S, verb-meaning effects emerged on an atypical time course. In the argument selection experiment, significant impairments in accuracy were observed only in PPA-G, accompanied by markedly atypical eye movement patterns.
This study revealed two distinct patterns of impaired verb-argument integration in PPA. In PPA-S, impaired verb-argument integration was observed in the argument access experiment, indicating impairments in basic semantic combinatory processes which likely relate to damage in ventral language pathways. In contrast, listeners with PPA-G showed marked impairments of argument selection, likely relating to damage to left inferior frontal regions.
在三种主要的 PPA 亚型中，句子理解受损，与语法障碍（PPA-G）和失语法（PPA-L）变体中理解复杂句子以及语义障碍（PPA-S）中理解单词的能力受损相关的表现模式不同。然而，对于 PPA 患者在句子理解过程中的基本组合过程，例如动词与主语及其宾语（动词-宾语整合）的整合，人们知之甚少。
本研究使用视觉世界眼动追踪技术，分别在患有 PPA（12 名 PPA-G、10 名 PPA-L 和 6 名 PPA-S）和神经典型老年人（15 名）中检查实时动词-宾语整合。两个基线实验分别使用非语言任务和名词理解来探测眼动控制。两个动词-宾语整合实验分别检查动词意义对（a）动词直接宾语的词汇访问（宾语访问）和（b）语义上适当的直接宾语的选择（宾语选择）的影响。仅对具有正确行为反应的试验进行眼动分析，从而可以区分准确性和在线处理。
眼动控制实验未显示 PPA 存在显著的障碍，而名词理解实验则显示 PPA-S 的准确性降低且眼动潜伏期延长，而 PPA-G 的影响较小。在宾语访问实验中，动词意义在 PPA-G 和 PPA-L 中正常促进宾语访问；在 PPA-S 中，动词意义的影响出现在非典型的时间过程中。在宾语选择实验中，仅在 PPA-G 中观察到准确性的显著障碍，伴有明显异常的眼动模式。
本研究揭示了 PPA 中两种不同的动词-宾语整合受损模式。在 PPA-S 中，在宾语访问实验中观察到动词-宾语整合受损，表明基本语义组合过程受损，这可能与腹侧语言通路的损伤有关。相比之下，患有 PPA-G 的听者表现出明显的宾语选择障碍，可能与左额下回区域的损伤有关。
