HOme-based Brain Monitoring With a GARment-EEG to Study Cognitive Decline in the Aging Population

General Inclusion Criteria: * Native Spanish speaker. * Agree to the examination procedures and tests. * Ability to involve a close family member or friend for functional evaluation. * Normal or corrected-to-normal color vision. * No medical condition requiring chronic systemic medication with psychoactive effects causing confusion. * No severe psychiatric (according to DSM-V) or neurological diseases (epilepsy with frequent seizures (\>1/month) in the last year, multiple sclerosis, etc.). * No diseases that may interfere with cognitive functions (renal insufficiency on hemodialysis, liver cirrhosis, chronic pulmonary disease with oxygen therapy, solid organ transplant, fibromyalgia, active cancer under treatment). * No severe hearing and/or visual impairments, neurodevelopmental, or psychomotor disorders. * No brain injuries that may interfere with cognitive functions (history of traumatic brain injury with parenchymal injury or macroscopic ischemic stroke of large extra-axial vessels or hemorrhagic stroke, brain surgery, brain tumors, or other causes that could result in acquired brain damage such as brain chemotherapy or radiotherapy). * No treatment with antipsychotic agents in the 6 months prior to the initial assessment. * No medical condition requiring chronic systemic medication with psychoactive effects causing confusion. No psychiatric or neurological medication. * No alcohol or drug abuse. * No serious health problems in the last 12 months (especially neurological or cardiac disorders). Inclusion Criteria 'Mild Dementia' group: * Diagnosis of Alzheimer's type dementia, based on a clinical and cognitive assessment conducted by a physician. * Diagnosis of vascular or mixed type dementia, based on a clinical and cognitive assessment conducted by a physician. * Lack of autonomy in: 1. basic activities according to the Barthel Index; 2. instrumental activities according to the Lawton Index. Both indices assess dependence associated with the diagnosis of dementia, distinguishing it from the diagnosis of mild cognitive impairment. Inclusion Criteria 'Mild Cognitive Impairment' group: * Diagnosis of mild cognitive impairment, based on a clinical and cognitive assessment conducted by a physician. * Preserved autonomy in: 1. basic activities according to the Barthel Index; 2. instrumental activities according to the Lawton Index. Both indices assess dependence associated with the diagnosis of dementia, distinguishing it from the diagnosis of mild cognitive impairment Inclusion Criteria 'Subjective Cognitive Decline' group: * Adherence to SCD-I criteria. * Attendance at primary care consultation with memory complaints lasting more than 6 months. * Absence of a diagnosis of mild cognitive impairment or dementia. * Onset of subjective cognitive decline in the last 5 years. * Concerns related to subjective cognitive decline (not associated with an acute event) expressed by the participant and/or an informant. * Cognitive performance within the normal range on cognitive tests (MMSE (Mini Mental State Exam) \< 26 / MIS (Memory Impairment Screen) \< 6). * No severe depressive symptoms, indicated by scores \> 17\* on the 30-item Geriatric Depression Scale. Inclusion criteria No impairment group: * Cognitive performance within the normal range on cognitive tests (MMSE \< 26 / MIS \< 6). * Absence of a diagnosis of mild cognitive impairment or dementia. * Not meeting the criteria for SCD-I \[21\]. * Independent person living in their own home. * No subjective memory complaints.