Neural correlates of cognitive intervention in persons at risk of developing Alzheimer's disease.

Cognitive training is an emergent approach that has begun to receive increased attention in recent years as a non-pharmacological, cost-effective intervention for Alzheimer's disease (AD). There has been increasing behavioral evidence regarding training-related improvement in cognitive performance in early stages of AD. Although these studies provide important insight about the efficacy of cognitive training, neuroimaging studies are crucial to pinpoint changes in brain structure and function associated with training and to examine their overlap with pathology in AD. In this study, we reviewed the existing neuroimaging studies on cognitive training in persons at risk of developing AD to provide an overview of the overlap between neural networks rehabilitated by the current training methods and those affected in AD. The data suggest a consistent training-related increase in brain activity in medial temporal, prefrontal, and posterior default mode networks, as well as increase in gray matter structure in frontoparietal and entorhinal regions. This pattern differs from the observed pattern in healthy older adults that shows a combination of increased and decreased activity in response to training. Detailed investigation of the data suggests that training in persons at risk of developing AD mainly improves compensatory mechanisms and partly restores the affected functions. While current neuroimaging studies are quite helpful in identifying the mechanisms underlying cognitive training, the data calls for future multi-modal neuroimaging studies with focus on multi-domain cognitive training, network level connectivity, and individual differences in response to training

Semantic Memory Functional MRI and Cognitive Function After Exercise Intervention in Mild Cognitive Impairment

Mild cognitive impairment (MCI) is associated with early memory loss, Alzheimer\u27s disease (AD) neuropathology, inefficient or ineffective neural processing, and increased risk for AD. Unfortunately, treatments aimed at improving clinical symptoms or markers of brain function generally have been of limited value. Physical exercise is often recommended for people diagnosed with MCI, primarily because of its widely reported cognitive benefits in healthy older adults. However, it is unknown if exercise actually benefits brain function during memory retrieval in MCI. Here, we examined the effects of exercise training on semantic memory activation during functional magnetic resonance imaging (fMRI). Seventeen MCI participants and 18 cognitively intact controls, similar in sex, age, education, genetic risk, and medication use, volunteered for a 12-week exercise intervention consisting of supervised treadmill walking at a moderate intensity. Both MCI and control participants significantly increased their cardiorespiratory fitness by approximately 10% on a treadmill exercise test. Before and after the exercise intervention, participants completed an fMRI famous name discrimination task and a neuropsychological battery, Performance on Trial 1 of a list-learning task significantly improved in the MCI participants. Eleven brain regions activated during the semantic memory task showed a significant decrease in activation intensity following the intervention that was similar between groups (p-values ranged 0.048 to 0.0001). These findings suggest exercise may improve neural efficiency during semantic memory retrieval in MCI and cognitively intact older adults, and may lead to improvement in cognitive function. Clinical trials are needed to determine if exercise is effective to delay conversion to AD

Can a serious game-based cognitive training attenuate cognitive decline related to Alzheimer's disease? Protocol for a randomized controlled trial.

BACKGROUND Alzheimer's disease (AD) is a major public health issue. Cognitive interventions such as computerized cognitive trainings (CCT) are effective in attenuating cognitive decline in AD. However, in those at risk of dementia related to AD, results are heterogeneous. Efficacy and feasibility of CCT needs to be explored in depth. Moreover, underlying mechanisms of CCT effects on the three cognitive domains typically affected by AD (episodic memory, semantic memory and spatial abilities) remain poorly understood. METHODS In this bi-centric, randomized controlled trial (RCT) with parallel groups, participants (planned N = 162, aged 60-85 years) at risk for AD and with at least subjective cognitive decline will be randomized to one of three groups. We will compare serious game-based CCT against a passive wait list control condition and an active control condition (watching documentaries). Training will consist of daily at-home sessions for 10 weeks (50 sessions) and weekly on-site group meetings. Subsequently, the CCT group will continue at-home training for an additional twenty-weeks including monthly on-site booster sessions. Investigators conducting the cognitive assessments will be blinded. Group leaders will be aware of participants' group allocations. Primarily, we will evaluate change using a compound value derived from the comprehensive cognitive assessment for each of three cognitive domains. Secondary, longitudinal functional and structural magnetic resonance imaging (MRI) and evaluation of blood-based biomarkers will serve to investigate neuronal underpinnings of expected training benefits. DISCUSSION The present study will address several shortcomings of previous CCT studies. This entails a comparison of serious game-based CCT with both a passive and an active control condition while including social elements crucial for training success and adherence, the combination of at-home and on-site training, inclusion of booster sessions and assessment of physiological markers. Study outcomes will provide information on feasibility and efficacy of serious game-based CCT in older adults at risk for AD and will potentially generalize to treatment guidelines. Moreover, we set out to investigate physiological underpinnings of CCT induced neuronal changes to form the grounds for future individually tailored interventions and neuro-biologically informed trainings. TRIAL REGISTRATION This RCT was registered 1st of July 2020 at clinicaltrials.gov (Identifier NCT04452864)

Exercise Training and Functional Connectivity Changes in Mild Cognitive Empairment and Healthy Elders

Background: Effective interventions are needed to improve brain function in mild cognitive impairment (MCI), an early stage of Alzheimer’s disease (AD). The posterior cingulate cortex (PCC)/precuneus is a hub of the default mode network (DMN) and is preferentially vulnerable to disruption of functional connectivity in MCI and AD. Objective: We investigated whether 12 weeks of aerobic exercise could enhance functional connectivity of the PCC/precuneus in MCI and healthy elders. Methods: Sixteen MCI and 16 healthy elders (age range = 60–88) engaged in a supervised 12-week walking exercise intervention. Functional MRI was acquired at rest; the PCC/precuneus was used as a seed for correlated brain activity maps. Results: A linear mixed effects model revealed a significant interaction in the right parietal lobe: the MCI group showed increased connectivity while the healthy elders showed decreased connectivity. In addition, both groups showed increased connectivity with the left postcentral gyrus. Comparing pre to post intervention changes within each group, the MCI group showed increased connectivity in 10 regions spanning frontal, parietal, temporal and insular lobes, and the cerebellum. Healthy elders did not demonstrate any significant connectivity changes. Conclusion: The observed results show increased functional connectivity of the PCC/precuneus in individuals with MCI after 12 weeks of moderate intensity walking exercise training. The protective effects of exercise training on cognition may be realized through the enhancement of neural recruitment mechanisms, which may possibly increase cognitive reserve. Whether these effects of exercise training may delay further cognitive decline in patients diagnosed with MCI remains to be demonstrated

Cognitive functions during migraine attacks

Tese de doutoramento, Medicina (Neurologia), Universidade de Lisboa, Faculdade de Medicina, 2015Background: Attack-related cognitive symptoms in migraine are frequent yet scarcely characterized and undervalued as contributors of disability. Conflicting evidence arose about an increased risk of cognitive decline in older migraine patients. Objectives: (1) to study the occurrence of cognitive symptoms in migraine attacks; (2) to evaluate objective evidence of cognitive dysfunction in migraine attacks and its neuronal correlates and (3) to study the effect of persisting migraine in cognitive function or cognitive decline in older adults. Methods: Occurrence of attack-related cognitive symptoms was detailed by systematic literature review and a cross-sectional clinical-based systematic survey; their relevance to disability was studied prospectively using headache diaries. An instrument (Mig-SCog) was developed, validated and tested to identify and quantify attack-related subjective cognitive symptoms. Cognitive function during attacks was evaluated by a systematic literature review and a clinical-based prospective two-period randomized cross-over study using an extensive neuropsychological battery. A briefer battery was tested in repeated applications in interictal patients and controls. Brain perfusion during attacks was studied with arterial spin labeling magnetic resonance imaging (ASL-MRI) and cortical response to a working memory task with blood-oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI). A prospective controlled cross-sectional population-based study of neuropsychological performance of older adults with persisting migraine and non-migraine headache was followed by a 5 years re-evaluation of the same sample, to screen for cognitive decline. Results: Cognitive symptoms were the most frequent non-migraine defining symptoms reported in the prodromic(37%) and headache(38%) phases of migraine attacks in a systematic review of 28 series, with a total sample of 8392 patients. Cognitive symptoms are also present in the postdromic or resolution phase, although fatigue (71%) is reported more often. Of 165 patients prospectively surveyed, 87% reported an average of 2.5 attack-related symptoms, over two-thirds executive (attention, processing efficiency and speed). Cognitive symptoms were ranked prospectively by 34 migraine patients recording 229 attacks, being second only to pain in terms of intensity and attack-related disability. An instrument to quantify migraine attack-related symptoms was constructed from a set of 43 candidate items, using factor analysis. The reduced 9 item Mig-SCog is fast to apply covering executive functions and language, having good internal consistency (Cronbachs’ alpha 0.82) and reliability (Cohen’s kappa 0.55) and high correlation with external validity measures such as the 43-candidate item list (rho=0.69) and the Cognitive Failures Questionnaires(rho=0.61). The Mig-SCog presents negligible recall bias (no difference in scores obtained during an attack or while headache free) and Migraine patients score it higher for migraine higher for migraine (7.9±4.6) than for non-headache pain (2.3±2.9, p<0.0006) or pain free (1.6±2.4, p<0.0006). Comparing Mig-SCog scores in migraine and tension-type headache patients, those were higher for migraine in all scale items (p<0.0001) except those related to naming (8 and 9). The AUC of Mig-SCog score for the diagnosis of Migraine was 0.835 (95% CI of 0.763-0.906, p< 0.0001) reinforcing specificity for migraine. Ten studies of neuropsychological evaluation during migraine attacks are available in the literature, only half had data allowing comparison of cognitive performance within and outside attacks (encompassing 163 migraine patients). All these were able to demonstrate some type of impairment (most often executive) although some bias could not be excluded from their study design. In our sample of 24 patients which completed an extensive neuropsychological evaluation in these two conditions (attack and headache-free) controlling for the majority of relevant bias (in particular the practice effect), performance was worse during the attack in the majority of cognitive tests, in particular in word reading speed (p=0.013), verbal learning (p=0.01), short term verbal recall with (p=0.01) and without (p=0.013) semantic cueing and delayed recall with (p=0.003) and without (p=0.05) semantic cues. Another sample of 24 interictal migraine patients and 24 matched controls performed equally in a shorter battery focused on executive functions that was applied twice with a short interval (average 45 days) to test the practice effect of repeated evaluations that was demonstrated in all tests, being significant in Stroop Interference test (p=0.002, multiplicity corrected); a meaningful score change was determined for each raw test scores. We were unable to find any relevant brain perfusion nor brain activation differences evoked by a working memory task during a spontaneous migraine without aura attack of an average intensity of 6.8 on a 0-10 VAS scale and an average duration of 16 hours in a sample of 13 women, compared to being headache-free. Persistent migraine or headache after the age of 50 related to worse performance in some neuropsychological tests (attention and processing speed in migraine patients, n=61; sematic memory and memory retrieval in non-migraine headache, n=50) in a population sample of 478 individuals tested extensively. After 5 years, 275 (57.5%) of the same sample were screened for cognitive decline, that occurred in 14.9% of the sample. Neither migraine nor non-migraine headache influenced the odds of decline. Discussion: Attack-related cognitive symptoms are very frequent, mostly executive and contribute to disability, supporting that they should be addressed as endpoint in clinical trials of acute migraine treatments and included in disability assessments. An efficient way to assess attack-related subjective cognitive symptoms in clinical practice or research is now available – the Mig-SCog. Although migraine-related reversible cognitive dysfunction was demonstrated during attacks, no advances on potential brain mechanisms underlying these findings were made. Interest is focused to obtain more functional data, with studies of evoked activation paradigms, functional connectivity and combined imaging and neurophysiological studies. Although persisting headache in older adults seems to influence executive performance, these changes are most likely adaptive and do not seem to influence the process of brain degeneration and associated cognitive decline

Cognitive function in healthy aging – A theoretical overview on the effects of cognitive training combined with Transcranial Direct Current Stimulation (tDCS)

Nas últimas décadas, e como consequência do aumento progressivo da esperança de vida, diversos estudos se têm focado na população idosas e, em específico, no envelhecimento cerebral e respetivas consequências no funcionamento cognitivo. Mesmo no envelhecimento saudável, existe uma série de alterações cognitivas que se podem traduzir em perdas ao nível da funcionalidade. É urgente investigar formas de atenuar os efeitos do envelhecimento na função cognitiva e manter a autonomia da população idosa. O treino cognitivo (TC) consiste numa técnica que visa a restauração, reorganização ou compensação das perdas cognitivas, promovendo a manutenção da funcionalidade e mitigando o declínio cognitivo. Por outro lado, a estimulação elétrica transcraniana (EET) emerge enquanto técnica não-invasiva de neuromodulação, que pode causar um impacto positivo no funcionamento cognitivo, através do envio de corrente elétrica de baixa intensidade para o crânio. Ainda que exista já evidência da eficácia destas técnicas, estão ainda pouco exploradas e aplicadas em Portugal. A presente revisão teórica visa explorar de que forma a aplicação combinada destas duas técnicas pode melhorar o funcionamento cognitivo no envelhecimento saudável.n recent decades, and as a consequence of the progressive increase of lifespan, several studies have been focusing on the elderly population and specifically on brain ageing and its consequences on cognitive functioning. Even in healthy ageing, there is a series of cognitive changes, which may result in functional losses. It is urgent to investigate ways of attenuating the effects of ageing on cognitive function and maintain the autonomy of the elderly population. Cognitive training (CT is a technique aimed at restoring, reorganizing or compensating cognitive losses, promoting the maintenance of functionality and delaying cognitive decline. On the other hand, Transcranial electrical stimulation (TES) emerges as a non-invasive neuromodulation technique that can have a positive impact on cognitive functioning, by sending a low-intensity electrical current to the skull. Although there is already evidence of the effectiveness of these techniques, they are still poorly explored and applied in Portugal. This theoretical overview aims to explore how the combined application of these two techniques can enhance cognitive function in healthy ageing.info:eu-repo/semantics/publishedVersio

The Association of Late-Life Depression, Cognitive Functioning, and Sleep Disorder in Aging

The continuing growth in the demographic of aging individuals in the United States creates concern for diseases of aging that are chronic, notably unipolar depressive disorders. The high rates of depression in the aging population are a concern because of the strong association between late-life depression and cognitive impairment. Poor cognitive functioning is a hallmark of aging related neurological disorders, the most prevalent being Alzheimer’s Disease (AD). Sleep disorder is a core symptom of depression, and is definitively associated with the development of mild cognitive impairment (MCI), the prodrome of AD. MCI is also characterized by similar types of sleep disturbance including sleep fragmentation, which consists of excessive awakenings during the night that leads to atypical suppression of night-time full awakenings and chronic sleep debt that impairs daytime attention and cognition as a consequence of poor sleep quality. The main hypothesis of this study is that current or historical depression in older adults will be associated with poor sleep quality and cognitive impairment. Participants (N=50) from 65-85 years were assessed to determine the impact of depression status on sleep disturbance and cognitive variables. Individuals endorsing current depression (n=9), history of diagnosed depression but no current depression (n=7), or no current depression (n=34) were tested for 7 nights using wrist actigraphy and self-report sleep diaries to assess various sleep parameters used to identify sleep disturbance. Memory consolidation was probed surrounding one night of sleep using a simple procedural memory task and one-month follow-up assessment was used to assess a variety of neurocognitive domains including immediate and delayed recall, visuospatial abilities, etc. Results from this study revealed that individuals with current depression showed poorer sleep quality (i.e. shorter sleep time, lower mean sleep efficiency, longer sleep latency, etc.) and self-reported more sleep disturbances and greater daytime dysfunction when compared with individuals with no current depression or depressive history (p’s \u3c .05). Results of impairment on cognitive tasks from participants with current depression or a history of diagnosed depression were not found. These results provide evidence of an association between sleep disturbance and late-life depression. Cognitive performance of depressed older adults warrant further exploration

Cognitive Aging

Given the global demographic shift towards an aging population, there is a pressing need to understand how aging affects cognition. This collection of articles, from across the globe, represents some of the diverse aspects of cognitive aging. These articles investigate the fundamental processes and mechanisms underlying the neural and cognitive changes associated with normal and pathological aging. They describe the many facets of cognition, memory, language and thinking that are affected by the aging process. The articles will hopefully fascinate readers, and entice them to learn more about how such research is conducted, as well as serving as avenues for exploration to compensate for deficits in cognitive function. The studies are cutting edge and offer insight into the development of the theories that best account for the changes in brain and behaviour that affect us all

Imaging of cognitive outcomes in patients with autoimmune encephalitis

Die Autoimmunenzephalitis ist eine kürzlich beschriebene entzündliche Erkrankung des zentralen Nervensystems, die Gedächtnisdefizite, Psychosen, oder epileptische Anfälle hervorrufen kann. Derzeit ist hingegen noch nicht ausreichend verstanden, welche pathologischen Veränderungen zu den kognitiven Defiziten führen und welche neuropsychologischen und bildgebenden Langzeitoutcomes zu erwarten sind. Anhand von strukturellen und funktionellen Bildgebungsanalysen zeigt diese Dissertation, dass kognitive Defizite auch nach der akuten Phase der Autoimmunenzephalitis fortbestehen können. Bei der LGI1-Enzephalitis gehen Gedächtnisdefizite mit fokalen strukturellen Läsionen im Hippocampus einher. Durch eine funktionelle Störung der Resting-State-Konnektivität des Default-Mode- und Salienznetzwerkes beeinträchtigen diese Hippocampusläsionen auch Hirnregionen außerhalb des limbischen Systems. Bei Patient:innen mit NMDA-Rezeptor-Enzephalitis finden sich in der longitudinalen neuropsychologischen Untersuchung trotz guter allgemeiner Genesung auch noch mehrere Jahre nach der Akutphase persistierende Defizite des Gedächtnisses und exekutiver Funktionen. Zuletzt zeigt eine transdiagnostische Analyse, dass der anteriore Hippocampus eine erhöhte Vulnerabilität gegenüber immunvermittelten pathologischen Prozessen aufweist. Diese Ergebnisse legen nahe, dass kognitive Symptome auch noch nach der Entlassung aus der stationären Behandlung fortbestehen können. Sowohl umschriebene strukturelle Hippocampusläsionen als auch Veränderungen in makroskopischen funktionellen Hirnnetzwerken tragen zur pathophysiologischen Erklärung dieser Symptome bei. Zudem erlauben diese Ergebnisse einen Einblick in neuroplastische Veränderungen des Gehirns und haben weitreichende Implikationen für die Langzeitversorgung und das Design zukünftiger klinischer Studien.Autoimmune encephalitis is a recently described inflammatory disease of the central nervous system that can cause memory deficits, psychosis, or seizures. The trajectory of cognitive dysfunction and the underlying long-term imaging correlates are, however, not yet fully understood. By using advanced structural and functional neuroimaging, this thesis shows that cognitive deficits persist beyond the acute phase. In LGI1 encephalitis, MRI postprocessing revealed that memory deficits are related to focal structural hippocampal lesions. These hippocampal lesions propagate to brain areas outside the limbic system through aberrant resting-state connectivity of the default mode network (DMN) and the salience network. In NMDA receptor encephalitis, a longitudinal analysis of neuropsychological data describes persistent cognitive deficits, especially in the memory and executive domains, despite good physical recovery several years after the acute disease. Lastly, a transdiagnostic analysis reveals that the anterior hippocampus is particularly vulnerable to immune-mediated damage. In conclusion, these results demonstrate that cognitive symptoms in autoimmune encephalitis can persist beyond discharge from neurological care. Both discrete structural hippocampal damage and changes in macroscopic functional networks shed light on the pathophysiological basis of these symptoms. These findings help to explain how the brain responds to pathological damage and have substantial implications for long-term patient care and the design of future clinical studies