Universal grammar in the frontotemporal dementia spectrum: evidence of a selective disorder in the corticobasal degeneration syndrome.

INTRODUCTION: While sentence comprehension has been reported to be defective in frontotemporal dementia (FTD), it is still unclear if this disorder reflects the presence of syntactic impairment, or may be attributed to other factors, such as executive or working memory dysfunction. In order to assess the status of syntactic knowledge in a group of patients belonging to the FTD spectrum, we investigated their ability to detect violations of Universal Grammar principles in a sentence judgement task.
METHODS: The group included four semantic dementia patients (SD), nine frontal variant of FTD patients (FvFTD), 15 progressive supranuclear palsy (PSP) patients, and 11 corticobasal degeneration syndrome (CBDS) patients. Their performance was compared to a group of 10 patients with mild probable Alzheimer disease (AD) and to 10 healthy volunteers. The patients underwent a standard aphasia test and a sentence comprehension test. The experimental study included five kinds of violations: semantic coherence (SC), verb-subject agreement (VSAgr), pronominalization involving clitic movement (ClM), interrogatives (WhS) and contrastive focus constructions (CFC).
RESULTS: The FTD patients performed within normal range in the aphasia test, and in the sentence comprehension test. Within the FTD subgroups, only patients with CBDS were significantly impaired in detecting three of the five kinds of violations. AD patients were also impaired in the detection of WhS and SC anomalies and in sentence comprehension. DISCUSSION: The present findings indicate that, within the FTD spectrum, an impairment of syntactic knowledge can be found only in CBDS patients, even in the absence of clinical evidence of aphasia.