Abstract
Verbal fluency refers to the ability to generate words quickly and efficiently according to predefined phonological or semantic criteria. Deficits in verbal fluency limit patients’ ability to communicate effectively and to function well in social setups. Multiple sclerosis (MS) patients suffer from various cognitive impairments, and some of them experience language deficits as well. The goal of this study is to examine the contribution of the dorsal and ventral language pathways to verbal fluency in MS patients. All patients (N = 33) underwent diffusion MRI (dMRI) and fluency measurements. Diffusion parameters were calculated along dorsal and ventral language-related pathways and their right-hemispheric homologs, identified individually in each patient. Significant correlations were found between fluency measures and mean fractional anisotropy (FA) in several pathways, including the left fronto-temporal arcuate fasciculus (AFft), bilateral inferior fronto-occipital fasciculus (IFOF), and bilateral frontal aslant tract. Along-tract correlations revealed a more selective pattern of associations: letter-based fluency was associated with FA in a segment of the left AFft (dorsal pathway), while category-based fluency was associated with FA in a segment of the right IFOF (ventral pathway). The observed pattern of associations, mapping letter-based fluency to the dorsal stream and category-based fluency to the ventral stream, fits well within the dual stream framework of language processing. Further studies will be necessary to assess whether these associations generalize to the typical adult population or whether they are tied to the clinical state.
Highlights
Verbal fluency concerns our ability to access and produce words quickly and efficiently, which is an essential prerequisite for effective communication and social functioning
We found a significant correlation between letterbased fluency and fractional anisotropy (FA) in a large segment of the left AFft, while category-based fluency correlated with FA in a posterior segment of the right inferior fronto-occipital fasciculus (IFOF)
Our results showed that segments of the left AFft and of the right IFOF were correlated with letter-based fluency and category-based fluency, respectively
Summary
Verbal fluency concerns our ability to access and produce words quickly and efficiently, which is an essential prerequisite for effective communication and social functioning. Tests of verbal fluency require search, access, selection, retrieval and pronunciation of as many words as possible in a restricted time period, based on a predefined criterion. This process may fail due to deficits in any of these cognitive components (Thompson-Schill et al, 1998; Troyer et al, 1998; Lacey et al, 2017). Fluency tasks are considered effective probes for executive function, and are commonly. Verbal Fluency Pathways in MS included in neuropsychological batteries that assess such executive skills (e.g., Kramer et al, 2014). Assessment of verbal fluency is conducted as part of the clinical protocol in many clinical populations with acute and degenerative conditions, including patients with multiple sclerosis, who are the focus of this study (Friend et al, 1999; Benedict et al, 2006; Grimberg Schneider, 2014; Gerstenecker et al, 2017)
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