A deficit in semantic word learning in Huntington's disease

Previous studies investigating language deficits in Huntington's disease (HD) have reported relatively preserved lexical and semantic systems. Nevertheless, some aspects such as semantic word learning have never been previously explored. With this aim, in two experiments we used a well-known contextual word-learning paradigm to study two groups of early-stage HD patients with matched controls. The task required participants to infer the meaning of new words by extracting and integrating semantic cues from different sentences in a self-paced reading paradigm. The results showed that patients displayed difficulties to learn the meaning of new words from the context of the sentences (Exp. 1), which was reflected as more errors and null responses compared to controls, as well as increased reading times in conditions where meaning had to be integrated. Besides, we explored to which degree these learning differences could be attributed to working memory (WM) deficits. In Exp. 2 we ruled out this hypothesis, showing that semantic word learning was still impaired when reducing WM load. As a control condition, we also reported that these deficits remained even though patients had no impairment accessing synonyms or semantically related words of real words. These results strongly suggest a semantic learning impairment despite apparently preserved semantic processing abilities in HD patients. This research adds to growing evidence on the existence of subtle language-related impairments in HD patients, more specifically in complex language learning tasks.