Cognitive deficits influence the quality of life of Parkinson’s disease (PD) patients. In order to reduce the impact of cognitive impairment in PD, cognitive rehabilitation programs have been developed. This study presents a systematic review and meta-analysis regarding the effectiveness of cognitive rehabilitation in non-demented PD patients. Twelve articles were selected according to PRISMA guidelines. The systematic review showed that attention, working memory, verbal memory, executive functions and processing speed were the most frequently improved domains. Meta-analysis results showed moderate effects on global cognitive status (g = 0.55) and working memory (g = 0.50); small significant effects on verbal memory (g = 0.41), overall cognitive functions (g = 0.39) and executive functions (g = 0.30); small non-significant effects on attention (g = 0.36), visual memory (g = 0.29), verbal fluency (g = 0.27) and processing speed (g = 0.24); and no effect on visuospatial and visuoconstructive abilities (g = 0.17). Depressive symptoms showed small effect (g = 0.24) and quality of life showed no effect (g = −0.07). A meta-regression was performed to examine moderating variables of overall cognitive function effects, although moderators did not explain the heterogeneity of the improvement after cognitive rehabilitation. The findings suggest that cognitive rehabilitation may be beneficial in improving cognition in non-demented PD patients, although further studies are needed to obtain more robust effects.

Although the use of transcranial electrical stimulation (tES) techniques on healthy population has been linked to facilitating language learning, studies on their effects on foreign language learning processes are scarce and results remain unclear. The objective of this study was to analyze whether tES enhances foreign language learning processes. Sixty-four healthy native Spanish-speaking participants were randomly assigned to four groups (transcranial direct current, transcranial random noise, tDCS-tRNS stimulation, or sham). They completed two intervention sessions with a two-week gap in between. During the first session the participants received stimulation (1.5 mA) while learning new English words and then performed recall and recognition tasks. Learning was assessed at follow-up, two weeks later. No differences in learning between groups were observed in the first session (F_(1,61)= .86; p = .36). At follow-up, significantly higher learning accuracy was observed after tRNS compared to sham (p = .037). These results suggest that tRNS could be helpful in improving the processes involved in foreign language vocabulary learning.

Several studies have analyzed the effects of transcranial direct current stimulation on verbal fluency tasks in non-clinical populations. Nevertheless, the reported effects on verbal fluency are inconsistent. In addition, the effect of other techniques such as transcranial random noise stimulation (tRNS) on verbal fluency enhancement has yet to be studied in healthy multilingual populations. This study aims to explore the effects of tRNS on verbal fluency in healthy multilingual individuals. Fifty healthy multilingual (Spanish, English and Basque) adults were randomly assigned to a tRNS or sham group. Electrodes were placed on the left dorsolateral prefrontal cortex and left inferior frontal gyrus. All participants performed phonemic and semantic verbal fluency tasks before, during (online assessment) and immediately after (offline assessment) stimulation in three different languages. The results showed significantly better performance by participants who received tRNS in the phonemic verbal fluency tasks in Spanish (in the online and offline assessment) and English (in the offline assessment). No differences between conditions were found in Basque nor semantic verbal fluency. These findings suggests that tRNS on the left prefrontal cortex could help improve phonemic, yet not semantic, fluency in healthy multilingual adults.

Emotion recognition is a core component of social cognition and is essential for effective interpersonal communication. A growing body of literature suggests that this ability is impaired in Alzheimer's disease (AD), although the magnitude and nature of the deficit remain unclear. This meta-analysis aimed to quantify emotion recognition impairments in individuals with AD relative to healthy older adults (HOA). A systematic search identified 24 eligible studies comparing emotion recognition performance in individuals with AD and HOA. Random-effects models were used to calculate pooled effect sizes (Hedges' g). Primary analyses were conducted after influence diagnostics, and sensitivity analyses examined the impact of influential studies. Subgroup analyses examined the role of stimulus modality, while meta-regressions assessed potential moderation by MMSE scores, age, and education. Publication bias analyses were also conducted. The primary meta-analysis revealed a large and statistically significant impairment in emotion recognition in AD (g = -1.059, p <.0001). MMSE scores significantly moderated the effect, with higher global cognitive status associated with smaller deficits. Age and education did not significantly influence outcomes. Subgroup analyses showed comparable impairments across facial and non-facial tasks, with no significant differences between stimulus modalities. Emotion recognition is substantially impaired in AD. Although the magnitude of this deficit is associated with global cognitive status, it is unlikely to be fully explained by it alone. These findings support the relevance of social cognitive dysfunction in AD, highlight the importance of more ecologically valid assessment paradigms, and have implications for person-centred care and everyday interpersonal functioning in dementia settings.