A network approach to subjective cognitive decline: Exploring multivariate relationships in neuropsychological test performance across Alzheimer's disease risk states.

Subjective cognitive decline (SCD) is characterized by subjective concerns of cognitive change despite test performance within normal range. Although those with SCD are at higher risk for developing further cognitive decline, we still lack methods using objective cognitive measures that reliably distinguish SCD from cognitively normal aging at the group level. Network analysis may help to address this by modeling cognitive performance as a web of intertwined cognitive abilities, providing insight into the multivariate associations determining cognitive status. Following previous network studies of mild cognitive impairment (MCI) and Alzheimer's dementia (AD), the current study centered upon the novel visualization and analysis of the SCD cognitive network compared to cognitively normal (CN) older adult, MCI, and AD group networks. Cross-sectional neuropsychological data from CIMA-Q and COMPASS-ND cohorts were used to construct Gaussian graphical models for CN (n = 122), SCD (n = 207), MCI (n = 210), and AD (n = 79) groups. Group networks were explored in terms of global network structure, prominent edge weights, and strength centrality indices. CN and SCD group networks were contrasted using the Network Comparison Test. Results indicate that CN and SCD groups did not differ in univariate cognitive performance or global network structure. However, measures of strength centrality, principally in executive functioning and processing speed, showed a CN-SCD-MCI gradient where subtle differences within the SCD network suggest that SCD is an intermediary between CN and MCI stages. Additional results may indicate a distinctiveness of network structure in AD, a reversal in network influence between age and general cognitive status as clinical impairment increases, and potential evidence for cognitive reserve. Together, these results provide evidence that network-specific metrics are sensitive to cognitive performance changes across the dementia risk spectrum and can help to objectively distinguish SCD group cognitive performance from that of the CN group.

Impact of Stimulation Frequency on Verbal Fluency Following Bilateral Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease.

OBJECTIVE: The effects of stimulation frequency on verbal fluency (VF) following subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson's disease (PD) are not well understood. The present study examines the impact stimulation frequency has on VF following bilateral STN-DBS in PD. METHODS: Prospective study of 38 consecutive patients with PD with low frequency STN-DBS (LFS) (n = 10) and high frequency STN-DBS (HFS) (n = 14), and a non-operated PD control group consisting of patients with fluctuating response to dopaminergic medication (n = 14) homogeneous in age, education, disease duration, and global cognitive function. Patients were evaluated on VF tasks (letter, semantic, action verbs, alternating). A one-way analysis of variance (ANOVA) was conducted to assess distinctions between groups. Pre- and post-surgical comparisons of fluencies were performed for operated groups. A mixed ANOVA was applied to the data to evaluate the interaction between treatment (HFS vs. LFS) and time (pre- vs. post-surgery). Strategy use (clustering and switching) was evaluated. RESULTS: Semantic and letter fluency performance revealed significant differences between HFS and LFS groups. Pre- and post-surgical comparisons revealed HFS negatively affected letter, semantic, and action fluencies, but LFS had no effect on VF. No interaction effect or main effect of treatment was found. Main effect of time was significant for semantic and action fluencies indicating a decrease in postoperative fluency performance. Patients with LFS produced larger average cluster sizes than patients with HFS. CONCLUSION: LFS may be less detrimental to VF, but these findings suggest that VF decline following STN-DBS is not caused by stimulation frequency alone.

Evolving trends in neuropsychological profiles of post COVID-19 condition: A 1-year follow-up in individuals with cognitive complaints.

Cognitive difficulties are reported as lasting sequelae within post COVID-19 condition. However, the chronicity of these difficulties and related factors of fatigue, mood, and perceived health have yet to be fully determined. To address this, the current longitudinal study aimed to clarify the trends of cognitive test performance and cognitive domain impairment following COVID-19 onset, and whether hospitalization influences outcomes. 57 participants who reported subjective cognitive difficulties after confirmed COVID-19 infection were assessed at baseline (~6 months post COVID-19) and follow-up (~15 months later) visits. Assessments included measures across multiple cognitive domains and self-report questionnaires of fatigue, mood, and overall health. Analyses were conducted in three stages: at the test score level (raw and adjusted scores), at the cognitive domain level, and stratified by hospitalization status during infection. Results at the test-score level indicate that cognitive performance remains relatively stable across assessments at the group level, with no significant improvements in any adjusted test scores at follow-up. Cognitive domain analyses indicate significant reductions in attention and executive functioning impairment, while memory impairment is slower to resolve. On self-report measures, there was a significant improvement in overall health ratings at follow-up. Finally, those hospitalized during infection performed worse on timed cognitive measures across visits and accounted for a larger proportion of cases with short-term and working memory impairment at follow-up. Overall, our findings indicate that cognitive difficulties persist both at test score and cognitive domain levels in many cases of post COVID-19 condition, but evidence suggests some improvement in global measures of attention, executive functioning and overall self-rated health. Furthermore, an effect of hospitalization on cognitive symptoms post COVID-19 may be more discernible over time.

Background Music and Memory in Mild Cognitive Impairment: The Role of Interindividual Differences.

BACKGROUND: Recent research has shown that background music may improve memory consolidation and retrieval. Nevertheless, in the clinical conditions preceding dementia such as mild cognitive impairment (MCI), there is no current evidence speaking to what effect background music during memory tasks has on impaired cognition. OBJECTIVE: Across three experiments, we investigated if background music is able to improve memory performance, the most impacted cognitive domain in amnestic MCI. METHODS: We tested the effect of background music by using a face recognition memory task in patients with amnestic MCI. In Experiment 1, we tested the effect of background music on memory when it was played solely during an encoding phase. In Experiment 2, we explored effects of background music when played during both encoding and recognition phases. In Experiment 3, we explored the role of musically induced arousal on memory. RESULTS: The main finding from these three experiments was that background music played during a memory task did not improve or worsen participant performance. However, when exposed to high-arousal music, memory performance was predicted by individual mood regulation. For low-arousal music conditions, there was a negative relationship between rating scores for music pleasantness and performance on the memory task. CONCLUSION: Our results suggest that the benefits of background music on memory in individuals with MCI are modulated by interindividual preferences towards music.

Post-COVID-19 fatigue: the contribution of cognitive and neuropsychiatric symptoms.

Fatigue in its many forms of physical, mental, and psychosocial exhaustion is a common symptom of post-COVID-19 condition, also known as "Long COVID." Persistent fatigue in COVID-19 patients is frequently accompanied by cognitive dysfunction and neuropsychiatric symptoms; however, less is known about the relationships between these components of post-COVID-19 condition and fatigue itself. Consequently, the present study sought to (1) distinguish the types of fatigue experienced by participants, and (2) investigate whether cognitive deficits across various domains and neuropsychiatric conditions predicted these different types of fatigue. The study included 136 COVID-19 patients referred for neuropsychological evaluation due to cognitive complaints 8 months on average after SARS-CoV-2 infection. Measures included self-reported fatigue (physical, cognitive, and psychosocial), neuropsychiatric questionnaires (assessing symptoms of depression, anxiety, apathy, and executive functioning), a comprehensive neuropsychological assessment, and self-reported quality of life and everyday functioning. Results showed that reports of clinical significant fatigue were pervasive in our sample (82.3% of participants), with physical fatigue rated highest on average relative to the subscale maximum. Elevated levels of apathy, anxiety, and executive dysfunction in neuropsychiatric measures along with executive and attentional difficulties on cognitive tests were found to be consistently important predictors among different types of fatigue. This implicates both cognitive and neuropsychiatric symptoms as predictors of fatigue in post-COVID-19 condition, and stresses the importance of a holistic approach in assessing and considering potential treatment for COVID-19 patients experiencing fatigue.

Neuropsychological deficits in patients with cognitive complaints after COVID-19.

BACKGROUND: While much of the scientific focus thus far has been on cognitive sequelae in patients with severe COVID-19, subjective cognitive complaints are being reported across the spectrum of disease severity, with recent studies beginning to corroborate patients' perceived deficits. In response to this, the aims of this study were to (1) explore the frequency of impaired performance across cognitive domains in post-COVID patients with subjective complaints and (2) uncover whether impairment existed within a single domain or across multiple. METHODS: Sixty-three patients with subjective cognitive complaints post-COVID were assessed with a comprehensive protocol consisting of various neuropsychological tests and mood measures. Cognitive test performance was transformed into T scores and classified based on recommended guidelines. After performing a principal component analysis to define cognitive domain factors, distributions of test scores within and across domains were analyzed. RESULTS: Results revealed pervasive impact on attention abilities, both as the singularly affected domain (19% of single-domain impairment) as well as coupled with decreased performance in executive functions, learning, and long-term memory. These salient attentional and associated executive deficits were largely unrelated to clinical factors such as hospitalization, disease duration, biomarkers, or affective measures. DISCUSSION: These findings stress the importance of comprehensive evaluation and intervention to address cognitive sequelae in post-COVID patients of varying disease courses, not just those who were hospitalized or experienced severe symptoms. Future studies should investigate to what extent these cognitive abilities are recuperated over time as well as employ neuroimaging techniques to uncover underlying mechanisms of neural damage.

Voluntary Language Switching in the Context of Bilingual Aphasia.

As studies of bilingual language control (BLC) seek to explore the underpinnings of bilinguals' abilities to juggle two languages, different types of language switching tasks have been used to uncover switching and mixing effects and thereby reveal what proactive and reactive control mechanisms are involved in language switching. Voluntary language switching tasks, where a bilingual participant can switch freely between their languages while naming, are being utilized more often due to their greater ecological validity compared to cued switching paradigms. Because this type of task had not yet been applied to language switching in bilingual patients, our study sought to explore voluntary switching in bilinguals with aphasia (BWAs) as well as in healthy bilinguals. In Experiment 1, we replicated previously reported results of switch costs and mixing benefits within our own bilingual population of Catalan-Spanish bilinguals. With Experiment 2, we compared both the performances of BWAs as a group and as individuals against control group performance. Results illustrated a complex picture of language control abilities, indicating varying degrees of association and dissociation between factors of BLC. Given the diversity of impairments in BWAs' language control mechanisms, we highlight the need to examine BLC at the individual level and through the lens of theoretical cognitive control frameworks in order to further parse out how bilinguals regulate their language switching.

Semantic Processing in Bilingual Aphasia: Evidence of Language Dependency.

Individuals with aphasia frequently show lexical retrieval deficits due to increased interference of semantically related competitors, a phenomenon that can be observed in tasks such as naming pictures grouped by semantic category. These deficits are explained in terms of impaired semantic control, a set of abilities that are to some extent dependent upon executive control (EC). However, the extent to which semantic control abilities can be affected in a second and non-dominant language has not been extensively explored. Additionally, findings in healthy individuals are inconclusive regarding the degree to which semantic processing is shared between languages. In this study, we explored the effect of brain damage on semantic processing by comparing the performance of bilingual individuals with aphasia on tasks involving semantic control during word production and comprehension. Furthermore, we explored whether semantic deficits are related to domain-general EC deficits. First, we investigated the naming performance of Catalan-Spanish bilinguals with fluent aphasia and age-matched healthy controls on a semantically blocked cyclic naming task in each of their two languages (Catalan and Spanish). This task measured semantic interference in terms of the difference in naming latencies between pictures grouped by the same semantic category or different categories. Second, we explored whether lexical deficits extend to comprehension by testing participants in a word-picture matching task during a mixed language condition. Third, we used a conflict monitoring task to explore the presence of EC deficits in patients with aphasia. We found two main results. First, in both language tasks, bilingual patients' performances were more affected than those of healthy controls when they performed the task in their non-dominant language. Second, there was a significant correlation between the speed of processing on the EC task and the magnitude of the semantic interference effect exclusively in the non-dominant language. Taken together, these results suggest that lexical retrieval may be selectively impaired in bilinguals within those conditions where semantic competition is higher, i.e.,- in their non-dominant language; this could possibly be explained by an excessive amount of inhibition placed upon this language. Moreover, lexico-semantic impairments seem to be at least somewhat related to conflict monitoring deficits, suggesting a certain degree of overlap between EC and semantic control.