Functional MRI evidence for the decline of word retrieval and generation during normal aging

International audienceThis fMRI study aimed to explore the effect of normal aging on word retrieval and generation. The question addressed is whether lexical production decline is determined by a direct mechanism, which concerns the language operations or is rather indirectly induced by a decline of executive functions. Indeed, the main hypothesis was that normal aging does not induce loss of lexical knowledge, but there is only a general slowdown in retrieval mechanisms involved in lexical processing , due to possible decline of the executive functions. We used three tasks (verbal fluency, object naming , and semantic categorization). Two groups of participants were tested (Young, Y and Aged, A), without cognitive and psychiatric impairment and showing similar levels of vocabulary. Neuropsychological testing revealed that older participants had lower executive function scores, longer processing speeds, and tended to have lower verbal fluency scores. Additionally, older participants showed higher scores for verbal automa-tisms and overlearned information. In terms of behav-ioral data, older participants performed as accurate as younger adults, but they were significantly slower for the semantic categorization and were less fluent for verbal fluency task. Functional MRI analyses suggested that older adults did not simply activate fewer brain regions involved in word production, but they actually showed an atypical pattern of activation. Significant correlations between the BOLD (Blood Oxygen Level Dependent) signal of aging-related (A > Y) regions and cognitive scores suggested that this atypical pattern of the activation may reveal several compensatory mechanisms (a) to overcome the slowdown in retrieval, due to the decline of executive functions and processing speed and (b) to inhibit verbal automatic processes. The BOLD signal measured in some other aging-dependent regions did not correlate with the behavioral and neuro-psychological scores, and the overactivation of these uncorrelated regions would simply reveal dedifferentia-tion that occurs with aging. Altogether, our results suggest that normal aging is associated with a more difficult access to lexico-semantic operations and representations by a slowdown in executive functions, without any conceptual loss

More than Words:Cross-Linguistic Exploration of Parkinson’s Disease Identification from Speech

This study investigates the effect of listeners’ first language and expertise on their perception of speech produced by people with Parkinson’s Disease (PD). We compared assessment scores and identification accuracy of expert and non-expert Czech and Dutch listeners on two tasks: perception of speech healthiness and recognition of sentence type intonation. We collected speech data from 30 Dutch speakers diagnosed with PD and 30 Dutch speaking healthy controls. Short phrases from intonation tasks and spontaneous monologues were used as stimuli in an online perception experiment. 40 people (20 expert and 20 non-expert listeners) participated. Results show that both expertise and language familiarity are important factors in perception of speech of people with PD, however differences in identification accuracy depend on the task type. In recognition of PD speech, there are prominent acoustic cues that trigger perception of “unhealthiness” in the non-expert listeners, while experience with phonetics may lead to a different focus in their perception of such cues. In intonation accuracy recognition, both Czech and Dutch expert groups outperform both non-expert groups, indicating the added value of phonetic experience for the prosodic task. Yet, there is a clear benefit for having Dutch as the first language for both tasks, as Dutch listeners performed more accurately in both healthiness and sentence type recognition tasks