Abstract
BackgroundOvert repetition of auditorily presented words can facilitate picture naming performance in both unimpaired speakers and individuals with word retrieval difficulties, but the underlying neurocognitive mechanisms and longevity of such effects remain unclear. This study used functional magnetic resonance imaging to examine whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from an auditory repetition task in healthy older adults.ResultsThe behavioral results showed that both short- and long-term facilitated items were named significantly faster than unfacilitated items, with short-term items significantly faster than long-term items. Neuroimaging analyses identified a repetition suppression effect for long-term facilitated items, relative to short-term facilitated and unfacilitated items, in regions known to be associated with both semantic and phonological processing. A repetition suppression effect was also observed for short-term facilitated items when compared to unfacilitated items in a region of the inferior temporal lobe linked to semantic processing and object recognition, and a repetition enhancement effect when compared to long-term facilitated items in a posterior superior temporal region associated with phonological processing.ConclusionsThese findings suggest that different neurocognitive mechanisms underlie short- and long-term facilitation of picture naming by an auditory repetition task, reflecting both phonological and semantic processing. More specifically, the brain areas engaged were consistent with the view that long-term facilitation may be driven by a strengthening of semantic-phonological connections. Short-term facilitation, however, appears to result in more efficient semantic processing and/or object recognition, possibly in conjunction with active recognition of the phonological form.
Highlights
Overt repetition of auditorily presented words can facilitate picture naming performance in both unimpaired speakers and individuals with word retrieval difficulties, but the underlying neurocognitive mechanisms and longevity of such effects remain unclear
A further analysis on the reaction time data showed a main effect for condition (F2,1155 = 55.431, p = < 0.001) and post-hoc pairwise comparisons identified significant differences between all conditions (p < 0.001) with both short- and long-term facilitated items named faster than unfacilitated items and short-term items faster than long-term facilitated items
The present study found that long-term facilitation was driven by modulation of activity in regions associated with both phonological and semantic processing
Summary
Overt repetition of auditorily presented words can facilitate picture naming performance in both unimpaired speakers and individuals with word retrieval difficulties, but the underlying neurocognitive mechanisms and longevity of such effects remain unclear. One common form of word retrieval treatment involves repeating a target name in the presence of the target picture This task is often framed as a phonological treatment and is assumed by some to improve word retrieval by targeting phonological representations. Such a task may improve word retrieval by increased semantic (fMRI) to investigate in healthy older adults the effects associated with a commonly used treatment technique on subsequent picture naming performance. Ease of access to the phonological level from the semantic system relies on the strength of these links [6,7] These three component processes of picture naming (i.e., semantic, phonological and connections between) represent the basic architecture of the lexical system shared by most theoretical models of word production. Phonological processing, has implicated the posterior portion of the inferior frontal gyrus (but see [16]), the superior temporal gyrus and the supramarginal gyrus of the parietal lobe [8,9,11,14,17,18]
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