tDCS and Cognitive Efficiency in Ageing

Normal aging is associated with a progressive decline in cognitive functions, especially memory. This decline in cognitive function can negatively impact the quality of life of older adults. Although there are currently few possibilities to prevent and/or slow the signs of cognitive decline, both those associated with age and neurodegenerative pathologies, one of the non-invasive brain stimulation techniques that has gained attention in recent years is Transcranial Direct Current Stimulation (tDCS). tDCS is a technique based on the application of a low-intensity (\< 2 mA) direct electrical current between two large-area electrodes placed on various surface areas of the head. Moreover, according to safety-related meta-analyses it is a very safe technique, without any major side effects, provided that internationally established safety protocols are taken into account in its application. This technique has recently been investigated as a potential treatment for both healthy elderly people and people with mild cognitive impairment and Alzheimer's disease in several cognitive variables, having shown encouraging results in working memory learning curves, modulation of plasticity and recognition tasks. This project aims to implement an intervention using transcranial direct current stimulation in healthy older adults, MCI and AD. The main objective is to test if there is an improvement in cognitive efficiency and if the changes are maintained over time (1 month). For this purpose, the effect of the technique will be studied on participants assigned to treatment and control groups, analyzing the possible modifications in the following cognitive variables: cognitive plasticity and learning potential, recognition and familiarity and false alarms.

The clinical trial protocol involves the recruitment of participants from three different groups: healthy older adults, individuals with mild cognitive impairment (MCI), and patients with Alzheimer's disease (AD). Participants will be randomly assigned to either a treatment group or a control group.

For the treatment group, transcranial direct current stimulation (tDCS) will be administered over a specified period using a standard protocol involving the application of low-intensity electrical current (\< 2 mA) through electrodes placed on specific scalp areas. The duration and frequency of stimulation will be predetermined based on scientific literature and established safety recommendations.

The control group will receive a sham procedure where a low-intensity current, having no effect on neuronal activity, will be applied to maintain treatment masking.

Prior to commencing the intervention, a baseline assessment of participants' cognitive functions will be conducted using a battery of standardized tests, including measures of cognitive plasticity, memory, attention, executive functions, and other relevant cognitive abilities.

During the intervention period, regular tDCS or placebo sessions will be conducted according to participants' assigned groups. Additionally, data on potential side effects and tolerability of the technique will be collected.

At the end of the intervention period, a post-treatment assessment will be conducted to determine any changes in participants' cognitive functions. These data will be compared to baseline assessments to ascertain the intervention's efficacy.

Furthermore, participants will be followed up for a period of at least one month after the intervention to evaluate the persistence of effects and any potential long-term effects.

It is important to emphasize that this protocol will adhere to all ethical and safety regulations established by relevant regulatory authorities and ethics committees. Participants will be fully informed about the procedures and risks involved, and their informed consent will be obtained before their participation in the study.

Eligibility Criteria:
Inclusion Criteria:

For the group of healthy older adults:

* MEC score greater than 26 points.
* GDS between 1 and 3.

For the MCI group:

* MEC score between 21 and 26 points.
* GDS between 1 and 3.

For the mild EA group:

* MEC score between 18 and 23 points.
* GDS between 3 and 4.

Exclusion Criteria:

* Presentation of contraindications to tDCS (presence of intracranial metal implants, intracranial hypertension, comitial risk).
* Significant asymptomatic neurovascular disease
* History of previous symptomatic stroke
* Alcohol or drug abuse/dependence
* Severe psychiatric symptoms
* Depressive symptoms higher than mild