Effects of repetitive paired associative stimulation on brain plasticity and working memory in Alzheimer's disease: a pilot randomized double-blind-controlled trial.

DESIGN: Pilot randomized double-blind-controlled trial of repetitive paired associative stimulation (rPAS), a paradigm that combines transcranial magnetic stimulation (TMS) of the dorsolateral prefrontal cortex (DLPFC) with peripheral median nerve stimulation. OBJECTIVES: To study the impact of rPAS on DLPFC plasticity and working memory performance in Alzheimer's disease (AD). METHODS: Thirty-two patients with AD (females = 16), mean (SD) age = 76.4 (6.3) years were randomized 1:1 to receive a 2-week (5 days/week) course of active or control rPAS. DLPFC plasticity was assessed using single session PAS combined with electroencephalography (EEG) at baseline and on days 1, 7, and 14 post-rPAS. Working memory and theta-gamma coupling were assessed at the same time points using the N-back task and EEG. RESULTS: There were no significant differences between the active and control rPAS groups on DLPFC plasticity or working memory performance after the rPAS intervention. There were significant main effects of time on DLPFC plasticity, working memory, and theta-gamma coupling, only for the active rPAS group. Further, on post hoc within-group analyses done to generate hypotheses for future research, as compared to baseline, only the rPAS group improved on post-rPAS day 1 on all three indices. Finally, there was a positive correlation between working memory performance and theta-gamma coupling. CONCLUSIONS: This study did not show a beneficial effect of rPAS for DLPFC plasticity or working memory in AD. However, post hoc analyses showed promising results favoring rPAS and supporting further research on this topic. (Clinicaltrials.gov-NCT01847586).

Cell-based serum anticholinergic activity assay and working memory in cognitively healthy older adults before and after scopolamine: An exploratory study.

BACKGROUND: A new cell-based serum anticholinergic activity (cSAA) assay that measures anticholinergic activity specifically at muscarinic M1 receptors and eliminates many of the drawbacks of the existing assay was developed by our team. AIMS: We aimed to study the relationship between changes in working memory and executive function with changes in cSAA using the new assay in cognitively healthy older adults. METHODS: Cognitively healthy participants aged 50 years and above, received a single dose of 0.4 mg of intravenous scopolamine. Cognition and cSAA levels were measured before and 30 min after receiving scopolamine. Cognition was measured using the Cambridge Neuropsychological Test Automated Battery. RESULTS: Ten participants were recruited, and nine (mean age = 69.8, SD = 9.5, range 59-86 years) completed the study. Following scopolamine, participants experienced an increase in cSAA (cSAA pre = 0.90 ± 0.97 vs cSAA post = 12.0 ± 3.70 pmol/L; t-test (df = (8) = -9.5, p < 0.001). In addition, there was an association between change in cSAA and changes in working memory (Spearman's ρ = 0.68, p = 0.042) and executive function (Spearman's ρ = 0.72, p = 0.027). CONCLUSIONS: In our sample of cognitively healthy older adults, the new cSAA assay was able to quantify the scopolamine induced increase in anticholinergic load which correlated significantly with the observed decline in working memory and executive function.

The Impact of Anticholinergic Burden on Functional Capacity in Persons With Schizophrenia Across the Adult Life Span.

Anticholinergic burden (ACB) from medications impairs cognition in schizophrenia. Cognition is a predictor of functional capacity; however, little is known about ACB effect on functional capacity in this population. This study assesses the relationship between ACB and functional capacity across the life span in individuals with schizophrenia after controlling for ACB effect on cognition. A cross-sectional analysis was performed with data collected from 6 academic tertiary health centers. Two hundred and twenty-three community-dwelling participants with schizophrenia or schizoaffective disorder were included in this study. Main variables were ACB, antipsychotic olanzapine equivalents, functional capacity, cognition, and negative symptoms. Simultaneous linear regression analyses were performed to assess the association between ACB, functional capacity, and cognition and then between ACB and cognition. A mediation analysis was then performed to examine whether cognition mediated ACB effect on functional capacity if there was an association between ACB and cognition. Mean age of participants was 49.0 years (SD = 13.1, range 19-79), and 63.7% of participants had severe ACB, ie, a total score of 3 or above. Regression analyses revealed that ACB, age, education, and cognition independently predicted functional capacity and that ACB predicted cognition among those aged 55 years and older. Mediation analysis showed that cognition did partially mediate the effect of ACB on functional capacity in this older cohort. In conclusion, people with schizophrenia are exposed to severe ACB that can have a direct negative impact on functional capacity after controlling for its impact on cognition. Reducing ACB could improve functional capacity and potentially real-world function in schizophrenia.

Associations of visual paired associative learning task with global cognition and its potential usefulness as a screening tool for Alzheimer's Dementia.

OBJECTIVE: Appropriate screening is integral to the early diagnosis and management of Alzheimer's Dementia (AD). The Paired Associates Learning (PAL) task is a digital cognitive task that is free of cultural, language, and educational biases. This study examined the association between the PAL task performance and global cognition and the usefulness of the PAL task as a screening tool for AD. DESIGN: Cross-sectional. SETTING: Academic hospital. METHODS: Twenty-five participants with AD and 22 healthy comparators (HC) were included. The Cambridge Neuropsychological Test Automated Battery PAL task and the Montreal Cognitive Assessment (MoCA) were used to assess cognition. We assessed the relationship between the PAL task and MoCA performance using Pearson correlation and linear regression. We also examined the PAL task's ability to distinguish between AD and HC participants using Receiver Operating Characteristic curve (ROC) analysis. MEASUREMENTS: MoCA Total Score had a strong positive correlation with PAL Stages Completed score (r = 0.8, p < 0.001), and a strong negative correlation with PAL Total Errors (adjusted) score (r = -0.9, p < 0.001). Further, PAL Total Errors (adjusted) score predicted the MoCA Total Score (F (4, 46) = 37.2, p < 0.001). On ROC analysis, PAL Total Errors (adjusted) score cut-off of 54 errors had 92% sensitivity and 86% specificity to detect AD. CONCLUSIONS: Performance on the PAL task is highly associated with global cognition. Further, the PAL task can differentiate patients with AD from HCs with high sensitivity and specificity. Thus, the PAL task may hold potential usage as an easy-to-administer screening tool for AD.

Effects of bilateral transcranial direct current stimulation on working memory and global cognition in older patients with remitted major depression: A pilot randomized clinical trial.

OBJECTIVES: To assess the effects of a 10-day course of bilateral anodal transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) on working memory and global cognition in elderly participants with remitted major depressive disorder at 14 days (primary outcome) and 90 days (secondary outcome) post intervention. DESIGN: Randomized double blind controlled trial (clinicaltrials.gov # NCT02212366). SETTING: Community dwelling outpatient setting. PARTICIPANTS: Sixty or older with previous single or recurrent episodes of major depression currently in full remission. INTERVENTION: A 10 day course of active or sham bilateral DLPFC anodal tDCS. MEASUREMENTS: (a) Working memory assessed by a computerized N back task, and (b) global cognition assessed by a standard paper and pencil neuropsychological test battery. RESULTS: Thirty-three participants, (mean (SD) age = 66. 5 (5.7) year) were enrolled, out of which 18 (mean (SD) age = 66. 3 (5.8) year) were randomized to active tDCS and 15 (mean (SD) age = 66. 7 (5.8) years) to sham tDCS. All randomized participants except one from the sham group -completed the tDCS course. There were no differences between the groups on working memory performance or global cognition at 14 or 90 days post intervention. Both groups showed promising changes in working memory and global cognition over time. CONCLUSIONS: tDCS was well tolerated in older patients with remitted MDD, however, as compared to the sham group, it did not improve working memory or global cognition. Future studies should investigate tDCS with alternative parameters to enhance cognition in this population.

Theta-Gamma Coupling and Working Memory in Alzheimer's Dementia and Mild Cognitive Impairment.

Working memory deficits are common among individuals with Alzheimer's dementia (AD) or mild cognitive impairment (MCI). Yet, little is known about the mechanisms underlying these deficits. Theta-gamma coupling-the modulation of high-frequency gamma oscillations by low-frequency theta oscillations-is a neurophysiologic process underlying working memory. We assessed the relationship between theta-gamma coupling and working memory deficits in AD and MCI. We hypothesized that: (1) individuals with AD would display the most significant working memory impairments followed by MCI and finally healthy control (HC) participants; and (2) there would be a significant association between working memory performance and theta-gamma coupling across all participants. Ninety-eight participants completed the N-back working memory task during an electroencephalography (EEG) recording: 33 with AD (mean ± SD age: 76.5 ± 6.2), 34 with MCI (mean ± SD age: 74.8 ± 5.9) and 31 HCs (mean ± SD age: 73.5 ± 5.2). AD participants performed significantly worse than control and MCI participants on the 1- and 2-back conditions. Regarding theta-gamma coupling, AD participants demonstrated the lowest level of coupling followed by the MCI and finally control participants on the 2-back condition. Finally, a linear regression analysis demonstrated that theta-gamma coupling (ß = 0.69, p < 0.001) was the most significant predictor of 2-back performance. Our results provide evidence for a relationship between altered theta-gamma coupling and working memory deficits in individuals with AD and MCI. They also provide insight into a potential mechanism underlying working memory impairments in these individuals.

Anticholinergic Burden and Cognition in Older Patients With Schizophrenia.

OBJECTIVE: Older individuals with schizophrenia are at risk of being treated with anticholinergic medications due to the prevalence of medical comorbidities and polypharmacy. High anticholinergic burden impairs cognition and is a risk factor for Alzheimer's dementia. Thus, we assessed the impact of anticholinergic burden on Alzheimer's dementia-related and schizophrenia-related cognitive functions in older patients with schizophrenia. METHODS: Anticholinergic burden was measured using the Anticholinergic Cognitive Burden scale (ACB) in 60 community-dwelling patients aged ≥ 50 years who met DSM-IV criteria for schizophrenia between May 2007 and November 2011. Cognitive domains affected early in the course of Alzheimer's dementia were assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB) Alzheimer's Dementia Battery and the Repeatable Battery for the Assessment of Neuropsychological Status. Two CANTAB tests of executive function were used to assess deficits common in schizophrenia. Regression analyses were used to assess the relationships between anticholinergic burden and cognition. A receiver operating characteristic curve was constructed to determine an ACB cutoff score to identify those at risk of cognitive impairment. RESULTS: ACB scores were associated with spatial working (P = .04) and immediate (P = .004) memory and visuospatial ability (P = .02) and showed a trend toward association with impaired learning (P = .06), but were not associated with attention, executive function, language, or reaction time. An ACB cutoff score of ≤ 1.5 can detect cognitive impairment with a sensitivity of 90.3% and specificity of 48.3%. CONCLUSIONS: High anticholinergic burden contributes to specific cognitive deficits in older individuals with schizophrenia that resemble those commonly observed early in the course of Alzheimer's dementia. The ACB is a potentially useful screening tool that can help identify patients at risk of developing anticholinergic-related cognitive impairment.

Extent of Dorsolateral Prefrontal Cortex Plasticity and Its Association With Working Memory in Patients With Alzheimer Disease.

Importance: The extent of dorsolateral prefrontal cortex (DLPFC) plasticity in Alzheimer disease (AD) and its association with working memory are not known. Objectives: To determine whether participants with AD had impaired DLPFC plasticity compared with healthy control participants, to compare working memory between participants with AD and controls, and to determine whether DLPFC plasticity was associated with working memory. Design, Setting, and Participants: This cross-sectional study included 32 participants with AD who were 65 years or older and met diagnostic criteria for dementia due to probable AD with a score of at least 17 on the Mini-Mental State Examination and 16 age-matched control participants. Participants were recruited from a university teaching hospital from May 2013 to October 2016. Main Outcomes and Measures: Plasticity of the DLPFC measured as potentiation of cortical-evoked activity using paired associative stimulation (a combination of peripheral nerve electrical stimulation and transcranial magnetic stimulation) combined with electroencephalography. Working memory was assessed with the n-back task (1- and 2-back) and measured using the A' statistic. Results: Among the 32 participants with AD, 17 were women and 15 were men (mean [SD] age, 76.3 [6.3] years); among the 16 controls, 8 were men and 8 were women (mean [SD] age, 76.4 [5.1] years). Participants with AD had impaired DLPFC plasticity (mean [SD] potentiation, 1.18 [0.25]) compared with controls (mean [SD] potentiation, 1.40 [0.35]; F1,44 = 5.90; P = .02; between-group comparison, Cohen d = 0.77; P = .01). Participants with AD also had impaired performances on the 1-back condition (mean [SD] A' = 0.47 [0.30]) compared with controls (mean [SD] A' = 0.96 [0.01]; Cohen d = 1.86; P < .001), with similar findings for participants with AD on the 2-back condition (mean [SD] A' = 0.29 [0.2]) compared with controls (mean [SD], A' = 0.85 [0.18]; Cohen d = 2.83; P < .001). Plasticity of DLPFC was positively associated with working memory performance on the 1-back A' (parameter estimate B [SE] = 0.32 [0.13]; standardized ß = 0.29; P = .02) and 2-back A' (B [SE] = 0.43 [0.15]; ß = 0.39; P = .006) across both groups after controlling for age, education, and attention. Conclusions and Relevance: This study demonstrated impaired in vivo DLPFC plasticity in patients with AD. The findings support the use of DLPFC plasticity as a measure of DLPFC function and a potential treatment target to enhance DLPFC function and working memory in patients with AD.

An optimal combination of MCCB and CANTAB to assess functional capacity in older individuals with schizophrenia.

INTRODUCTION: Cognitive deficits predict functional capacity in patients with schizophrenia including in late life. The MATRICS Consensus Cognitive Battery (MCCB) and the Cambridge Neuropsychological Test Automated Battery (CANTAB) are widely used to assess cognition in this population. The aim of this study was to determine a minimal set of subtests across the two batteries that would be strongly associated with functional capacity in older patients with schizophrenia. METHODS: Sixty participants age 50 years or older with a diagnosis of schizophrenia or schizoaffective disorder and 30 control participants were enrolled. Cognition was assessed using the MCCB and the CANTAB. Functional capacity was assessed using the USCD Performance-based Skills Assessment (UPSA). Stepwise linear regressions were performed to determine the best set of cognitive tests associated with functional capacity. RESULTS: UPSA total score was negatively correlated with age and positively correlated with education and the MCCB global score. Most of the MCCB domains and subtests, and several of the CANTAB subtests correlated with UPSA total score. In the regression model, MCCB global score accounted for 42.5% of UPSA variance. In contrast, a combination of only four subtests (processing speed and verbal learning from the MCCB, and affective information processing and working memory from the CANTAB) accounted for 60% of UPSA variance. CONCLUSIONS: Performance on MCCB and CANTAB is strongly associated with functional capacity in older patients with schizophrenia. A selective combination of MCCB and CANTAB subtests may be as effective in assessing functional capacity in late life schizophrenia. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The influence of medical burden severity and cognition on functional competence in older community-dwelling individuals with schizophrenia.

OBJECTIVE: Cognition predicts functional competence among individuals with schizophrenia across the lifespan. However, as these individuals age, increasing levels of medical burden may also contribute to functional deficits both directly and indirectly through cognition. Thus, we assessed the relationship among, cognition, medical burden, and functional competence in older individuals with schizophrenia. METHODS: We analyzed data obtained from 60 community-dwelling participants with schizophrenia and 30 control participants aged 50 or above. Cognition was assessed using the MATRICS Consensus Cognitive Battery (MCCB), functional competence was assessed using the USCD Performance-Based Skills Assessment (UPSA), and medical burden was assessed using the Cumulative Illness Rating Scale for Geriatrics (CIRS-G). Group differences were assessed using independent samples t-tests or chi-square tests. Mediation analyses using bootstrapping techniques were used to assess whether cognition mediated the effects of medical burden on functional competence. RESULTS: Participants with schizophrenia had higher levels of medical burden, cognitive deficits, and functional impairments. In participants with schizophrenia, cognition, but not medical burden, predicted functional competence after adjusting for age, education, gender, clinical symptoms, and anticholinergic burden of medications. In control participants, cognition and medical burden both predicted functional competence after adjusting for age, education, and gender. Further, cognition was found to fully mediate the association between medical burden and functional competence in control participants. CONCLUSION: Cognition is a robust predictor of functional competence among older individuals with schizophrenia, regardless of medical burden. Cognitive deficits associated with schizophrenia may mask any further cognitive impairment associated with medical burden and its impact on function.