Effects of Transcranial Direct Current Stimulation Associated With Cognitive Training in Alzheimer's Disease

Alzheimer's disease (AD) is characterized by a progressive decline in cognitive functions, interfering with autonomy and independence. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM 5), mnemonic dysfunction in AD must be related to aphasia, apraxia, agnosia, or changes in executive function. The clinical picture of the disease can be described as mild, moderate and severe. In the mild phase, the patient is disoriented and with difficulties in thinking, in later stages memory lapses become more intense and frequent. The symptoms of apraxia, aphasia and agnosia appear, causing a noticeable impact on the performance of simple daily activities, and neuropsychiatric and behavioral symptoms are expressed. Existing pharmacological treatments for AD treatment are able to minimize the symptoms of the disease, but are not able to promote cure. Therefore, studies have sought to better understand non-pharmacological strategies, aiming at optimizing the benefits of using the drug. Studies have suggested that tDCS promotes significant effects on cognitive processes assessed through cognitive tasks, not only in healthy individuals but also in clinical populations. Cognitive training (TCog) has similarly shown excellent results in the treatment of cognitive deficits due to AD. Thus, the present study aims to investigate when (before, during or after) the tDCS should be applied to potentiate the effects of TCog in people with AD by comparing four protocols of application of neurostimulation associated with TCog.

It consists of a randomized, triple-blind, placebo-controlled clinical trial. The AETCC must be associated with the Tcog. Patients diagnosed in mild to moderate AD will be randomized into four groups: G1, aETCC before TCog; G2, aETCC during TCog; G3 aETCC after TCog and G4: simulated aETCC during TCog. Groups G1, G2 and G3 will receive the active current, while G4 will receive the simulated current. In each condition, an initial baseline assessment (T0) will be performed after 12 sessions (T1) and three weeks after the end of interventions (T2). The outcomes evaluated will be: cognition, executive function, functionality, neuropsychiatric symptoms and occupational performance. For all analyzes, SPSS (Statistical Package for Social Sciences - SPSS Inc, Chicago IL, USA) for Windows, Version 20.0, will be used and considered as significant, an alpha value of 5% (p \<0.05 ).

Eligibility Criteria:
Inclusion Criteria:

Patients will be included in this study following the following requirements: (a) age between 55 and 85 years; (b) probable diagnosis AD; (c) scores higher than 18 on the Mini Mental State Examination (MMSE); (e) did not receive regular cognitive intervention within 3 months prior to the start of this clinical trial.

Exclusion Criteria:

* Patients will be excluded from this study while not meeting the following criteria: (a) individuals with severe metabolic and / or cardiac disorders, alcoholism, focal neurological disorders and associated psychiatric disorders; (b) use of hypnotics and benzodiazepines two weeks prior to study initiation; or (c) use of medication with cholinergic inhibitors and memantine for more than two months prior to this clinical trial; (d) or with any condition that could impair the neuropsychological assessment process or receive a cognitive intervention protocol from the study will be excluded from the study. In addition, participants with transient or definitive pacemakers, cochlear implants, or intracranial aneurysm clips will be excluded; (e) individuals with a history of seizures; (f) the presence of tumors, epilepsy or substance abuse.