Verbal fluency difficulties in aphasia: A combination of lexical and executive control deficits

The role of language-related functional brain regions and white matter tracts in network plasticity of post-stroke aphasia

The neural mechanisms underlying language recovery after a stroke remain controversial. This review aimed to summarize the plasticity and reorganization mechanisms of the language network through neuroimaging studies. Initially, we discussed the involvement of right language homologues, perilesional tissue, and domain-general networks. Subsequently, we summarized the white matter functional mapping and remodeling mechanisms associated with language subskills. Finally, we explored how non-invasive brain stimulation (NIBS) promoted language recovery by inducing neural network plasticity. It was observed that the recruitment of right hemisphere language area homologues played a pivotal role in the early stages of frontal post-stroke aphasia (PSA), particularly in patients with larger lesions. Perilesional plasticity correlated with improved speech performance and prognosis. The domain-general networks could respond to increased "effort" in a task-dependent manner from the top-down when the downstream language network was impaired. Fluency, repetition, comprehension, naming, and reading skills exhibited overlapping and unique dual-pathway functional mapping models. In the acute phase, the structural remodeling of white matter tracts became challenging, with recovery predominantly dependent on cortical activation. Similar to the pattern of cortical activation, during the subacute and chronic phases, improvements in language functions depended, respectively, on the remodeling of right white matter tracts and the restoration of left-lateralized language structural network patterns. Moreover, the midline superior frontal gyrus/dorsal anterior cingulate cortex emerged as a promising target for NIBS. These findings offered theoretical insights for the early personalized treatment of aphasia after stroke.

Microstructural analysis of verbal fluency performance in relapsing-remitting multiple sclerosis based on the impact of disability level

Verbal fluency (VF) evaluates language and cognitive abilities. This study compared VF in Relapsing-Remitting Multiple Sclerosis (RRMS) and healthy controls (HC), examining variables including correct responses (CR), mean cluster size (MCS), switches (S), and fluency difference score (FDS). RRMS participants were subgrouped by Expanded Disability Status Scale (EDSS), to explore the relationship between MS severity and VF. Twenty-four RRMS participants and matched HCs underwent Mini-Mental State Exam and VF Test. Statistical analysis compared VF between RRMS subgroups based on severity levels, and in HC. RRMS significantly impacted the CR, and S (CRSF p = 0.01, SSF p = 0.002; CRPF=0.002, SPF p = 0.002), while there was no significant difference in FDS between RRMS groups (p = 0.9). No significant relationship was found between EDSS scores, and VF subtests (CRSF p = 0.061, MCSSF p = 0.46, SSF p = 0.051, CRPF p = 0.521, MCSPF p = 0.966, SPF p = 0.599). In RRMS, our results demonstrate impairments in all VF parameters except the MCSSF+PF, and FDS. This study suggests that intact MCSSF+PF may reflect preserved verbal memory and word recall, while significant switching differences may indicate impaired cognitive flexibility. Similar FDS to those of HC suggest that no performance discrepancy in subtests in RRMS. Intact MCS might be a distinctive pattern in the early clinical stage of MS.

Clustering and Switching in Semantic Verbal Fluency: Their Development and Relationship with Word Productivity in Typically Developing Greek-Speaking Children and Adolescents

Performance in semantic verbal fluency (SVF) tasks, mainly measured by the number of words of a particular semantic category produced within a limited time, is a widely accepted measure of cognitive functioning used in the neuropsychological assessment of children and adults. Two strategic processes, Clustering and Switching (C&S) have been proposed to underlie fluency processes and affect performance in the task. However, few studies have reported on the development of those cognitive strategies and their relationship with word productivity in typically developing children. Even fewer studies have covered a broad developmental period from preschool to adolescence or measured the effect of contextual factors in this relationship. Based on a sample of 472 typically developing Greek-speaking children aged 4;0 to 16;11 years, we investigated the development of SVF performance and reported on the degree to which it is affected by C&S strategies, children's sex, and level of parental education. Results revealed a large effect of age on word productivity and on the use of C&S strategies. Two switching factors (number of clusters and number of switches) and two clustering factors (mean cluster size and a novel measure, maximum cluster size), appeared to be significantly associated with word productivity, with the largest effect being attributed to the two switching factors. C&S factors, together with children's age and parental education, predicted 91.7% of the variance in the SVF score. Children's sex was not found to have a significant effect on either word productivity or C&S strategies. Results are discussed for their theoretical implications on the strategic processes underlying word production in typically developing children.

Impacts of motor phenotype on cognitive function in patients with Parkinson's disease 1 year after subthalamic-nucleus deep brain stimulation

BACKGROUND

Parkinson's disease (PD) is a neurological disorder that affects both motor and cognitive functioning. This study aimed to examine the impact of motor phenotype on cognitive function 1 year after subthalamic-nucleus deep brain stimulation (STN-DBS).

METHODS

The prospectively collected data of 37 patients with PD were retrospectively analyzed. The patients were divided into two group according to their motor phenotype: the postural instability and gait disturbance (PIGD) group comprised 16 patients, and the tremor-dominant (TD) group comprised 21 patients. The clinical characteristics and cognitive functions of all patients were examined at baseline and at the 1-year follow-up after STN-DBS.

RESULTS

The data showed that STN-DBS significantly improved motor functions (P < 0.05). A repeated-measures analysis of variance indicated a considerable group × time interaction impact on the memory quotient score (P < 0.001) and T_min (P = 0.033).

CONCLUSIONS

A distinct relationship between the neuropsychological spectrum and motor phenotype of PD patients was observed at the 1-year follow-up after STN-DBS, with worse cognitive outcomes in patients with the PIGD phenotype. Geriatr Gerontol Int 2023; 23: 85-90.