Abstract
It is well established that off-line sentence judgment tasks (oSJTs) typically rely on phonological working memory (WM), beyond specific linguistic processing. Nevertheless, empirical findings suggest that a juvenile level of performance in an oSJT could be associated with the recruitment of age-specific additional supportive neural network in healthy aging. In particular, in one of our previous study, healthy elderlies showed the additional activation of associative visual cortices when compared with young controls. We suggested that age-related hyperactivations, during an auditory sentence judgment task, might represent the neurofunctional correlate of the recruitment of compensatory strategies that are necessary to maintain a juvenile level of performance. To explicitly test this hypothesis we adopted repetitive transcranial magnetic stimulation (rTMS). Twelve healthy elderlies and 12 young participants were engaged in an off-line semantic plausibility judgment task while rTMS was delivered over: (1) the left inferior frontal gyrus (LIFG; i.e., a core region of the WM network); (2) the precuneus; and (3) a Control Site (vertex). Results showed a significant main effect of Stimulation Site and a significant Group-by-Stimulation Site interaction effect. In particular, the rTMS stimulation of the LIFG slowed down reaction times (RTs) both in young and healthy elderly participants, while only healthy elderlies showed an increment of RTs during the stimulation of the precuneus. Taken together our results further support the idea that the maintenance of a juvenile level of performance in graceful aging may be associated with task-specific compensatory processes that would manifest them-selves, from the neurofunctional point of view, by the recruitment of additional neural supportive regions.
Highlights
Age-Related Changes in Working Memory Can Affect Sentence ComprehensionWhen one has to face with spoken messages the verbal information becomes available a bit at time and, temporally discontinuous inputs must be bound together to let the meaning of the entire message emerge
Age-Related Changes in Sentence Comprehension (Caplan and Waters, 1999; Waters and Caplan, 2005; Caplan et al, 2011), the contribution of this temporary storage and processing system is critical for post-interpretative processes that are typically called into cause during off-line sentence judgment tasks
We investigated the neurofunctional signatures of age-related changes underlying an off-line sentence judgment tasks (oSJTs)
Summary
Age-Related Changes in Working Memory Can Affect Sentence ComprehensionWhen one has to face with spoken messages the verbal information becomes available a bit at time and, temporally discontinuous inputs must be bound together to let the meaning of the entire message emerge. Age-Related Changes in Sentence Comprehension (Caplan and Waters, 1999; Waters and Caplan, 2005; Caplan et al, 2011), the contribution of this temporary storage and processing system is critical for post-interpretative processes (i.e., processes that occur after the meaning of sentences has been extracted) that are typically called into cause during off-line sentence judgment tasks (oSJTs). Some behavioral studies suggest that, while the processing of plausible sentences (PSs; true sentences) may just be based on the activation of the semantic information conveyed by the sentence it-self, the processing of false sentences may involve additional cognitive steps as, in this last case, subjects have to solve a conflict between the sentence information stored in the WM and the semantic knowledge stored in long-term memory (Collins and Quillian, 1969; Glass and Holyoak, 1974). The task resembles the typical recall of a trace from WM, while in the second case (i.e., with false sentences) participants may rely on additional reasoning, problem-solving or mental imagery skills
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