Executive functions in primary progressive aphasia: A meta-analysis.

Executive functions (EFs) refer to a set of cognitive processes, specifically shifting, inhibition, updating of working memory, and are involved in the cognitive control of behavior. Conflicting results have been reported regarding impairments of EFs in Primary Progressive Aphasia (PPA). We performed a multi-level meta-analysis to confirm whether deficits of EFs exist in this population, focusing on a common EFs composite, and the components shifting, inhibition and updating separately. We included 141 studies that report on 294 EFs tasks. The overall mean weighted effect size was large (d = -1,28), indicating poorer EFs in PPA as compared to age-matched cognitively healthy controls. Differences between effect sizes of the EFs components were not significant, indicating all components are affected similarly. Overall, moderator analysis revealed that PPA variant and disease duration were significant moderators of performance, while task modality and years of education were not. The non-fluent/agrammatic PPA and the logopenic PPA variants were similarly affected, but the semantic variant was affected to a lesser extent. We discuss implications for clinical and research settings, and future research.

A Systematic Review of Transcranial Direct Current Stimulation in Primary Progressive Aphasia: Methodological Considerations.

A variety of tDCS approaches has been used to investigate the potential of tDCS to improve language outcomes, or slow down the decay of language competences caused by Primary Progressive Aphasia (PPA). The employed stimulation protocols and study designs in PPA are generally speaking similar to those deployed in post-stroke aphasic populations. These two etiologies of aphasia however differ substantially in their pathophysiology, and for both conditions the optimal stimulation paradigm still needs to be established. A systematic review was done and after applying inclusion and exclusion criteria, 15 articles were analyzed focusing on differences and similarities across studies especially focusing on PPA patient characteristics (age, PPA variant, language background), tDCS stimulation protocols (intensity, frequency, combined therapy, electrode configuration) and study design as recent reviews and group outcomes for individual studies suggest tDCS is an effective tool to improve language outcomes, while methodological approach and patient characteristics are mentioned as moderators that may influence treatment effects. We found that studies of tDCS in PPA have clinical and methodological and heterogeneity regarding patient populations, stimulation protocols and study design. While positive group results are usually found irrespective of these differences, the magnitude, duration and generalization of these outcomes differ when comparing stimulation locations, and when results are stratified according to the clinical variant of PPA. We interpret the results of included studies in light of patient characteristics and methodological decisions. Further, we highlight the role neuroimaging can play in study protocols and interpreting results and make recommendations for future work.

Constraint-induced aphasia therapy versus intensive semantic treatment in fluent aphasia.

OBJECTIVE: The authors compared the effectiveness of 2 intensive therapy methods: Constraint-Induced Aphasia Therapy (CIAT; Pulvermüller et al., 2001) and semantic therapy (BOX; Visch-Brink & Bajema, 2001). METHOD: Nine patients with chronic fluent aphasia participated in a therapy program to establish behavioral treatment outcomes. Participants were randomly assigned to one of two groups (CIAT or BOX). RESULTS: Intensive therapy significantly improved verbal communication. However, BOX treatment showed a more pronounced improvement on two communication-namely, a standardized assessment for verbal communication, the Amsterdam Nijmegen Everyday Language Test (Blomert, Koster, & Kean, 1995), and a subjective rating scale, the Communicative Effectiveness Index (Lomas et al., 1989). All participants significantly improved on one (or more) subtests of the Aachen Aphasia Test (Graetz, de Bleser, & Willmes, 1992), an impairment-focused assessment. There was a treatment-specific effect. BOX treatment had a significant effect on language comprehension and semantics, whereas CIAT treatment affected language production and phonology. CONCLUSION: The findings indicate that in patients with fluent aphasia, (a) intensive treatment has a significant effect on language and verbal communication, (b) intensive therapy results in selective treatment effects, and (c) an intensive semantic treatment shows a more striking mean improvement on verbal communication in comparison with communication-based CIAT treatment.

Cognitive, linguistic and affective disturbances following a right superior cerebellar artery infarction: a case study.

The cerebellar cognitive affective syndrome (CCAS) is a neurobehavioral syndrome that may develop after congenital and acquired cerebellar lesions. The syndrome consists of deficits in executive functioning, spatial cognition, visual-spatial memory and language and also involves personality and behavioral changes. We describe a 58-year-old right-handed man who in addition to affective disturbances presented with a unique combination of cognitive and linguistic deficits following an ischemic infarction in the vascular territory of the right superior cerebellar artery (SCA). Neurocognitive and neurolinguistic examinations were performed in the acute phase (10 days post-onset) and lesion phase (four weeks post-onset) of the stroke. A Tc-99m-ECD SPECT study was performed five weeks after the stroke. Acute phase data revealed a generalized cognitive decline and mild transcortical sensory aphasia. In the lesion phase, the neurobehavioral tableau was dominated by executive dysfunctions, disrupted divided attention, disturbed visual-spatial organization and behavioral abnormalities. Neurolinguistic investigations disclosed visual dyslexia and surface dysgraphia. Reading of words and visual lexical decision tasks of words and nonwords were severely defective and predominantly characterized by visual errors. In addition, writing irregular and ambiguous words resulted in regularization errors (phonologically plausible errors based on phoneme-grapheme correspondence rules). In the absence of any structural damage in the supratentorial brain regions, a quantified SPECT study showed a relative hypoperfusion in the right cerebellar hemisphere and the left medial frontal lobe. CCAS is for the first time reported in association with visual dyslexia and surface dysgraphia. We hypothesize that the cognitive and linguistic deficits might result from functional disruption of the cerebellar-encephalic pathways, connecting the cerebellum to the frontal supratentorial areas which subserve attentional and planning processes. This phenomenon of crossed cerebellar-cerebral diaschisis is supported by SPECT findings revealing a hypoperfusion in the anatomoclinically suspected brain regions. The constellation of cognitive, linguistic and behavioral symptoms adds new evidence to the multifaceted area of cerebellar neurocognition and demonstrates that the cerebellum might play a crucial role in cognitive, linguistic, and affective processing.

Impairment of syntax and lexical semantics in a patient with bilateral paramedian thalamic infarction.

Bilateral vascular thalamic lesions are rare. Although a variety of neurobehavioral manifestations have been described, the literature is less documented with regard to accompanying linguistic disturbances. This article presents an in-depth neurolinguistic analysis of the language symptoms of a patient who incurred bilateral paramedian ischemic damage of the thalamus. In the post-acute phase of the stroke, a unique combination of transcortical sensory aphasia with syntactic impairment was found. Because of this atypical semiological association, additional analyses of spontaneous speech were performed. In spite of the typological affinity with the grammatic characteristic of marked simplification of syntax observed in Broca's aphasia, only a wordclass specific, lexical-semantic deficit for verbs was objectified. The hypothesis that lexical-semantic disturbances in our patient might result from a functional deafferentiation of both thalami with the frontal lobe is supported by: (1) associated neuropsychological deficits of frontal origin and (2) frontal-like behavioral disturbances.