tDCS and Cognitive Efficiency (FRtDCS)

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 stimulation time was 20 minutes, with an initial and final ramp of 30 seconds so that the participant could adapt to the sensation of the current. 10 sesions. Constant current intensity of 2 mA The anode was placed on position F7, coinciding with the dorsolateral prefrontal cortex, and the cathode was placed on Fp2, coinciding with the right supraorbital area (rSO).

10 sessions of tDCS stimulation on dorsolateral prefrontal cortex with the apparatus HDC stimulator (Newronika TM)

The sham group received direct current only on the ramps to generate a sensation of the effect.10 sessions

The evaluator reads a 16-word shopping list in five different essays and in each of them the evaluated person must mention those words that he or she remembers. After 20 minutes, the subject is asked to remember them again

The digits forward task assesses immediate recall. It requires the participant to repeat a sequence of numbers in the same order in which they were read. On the digits backward task, the subject must repeat a sequence of numbers in the reverse order of their presentation. The task is used to assess working memory.

The Half condition included two lists of 50 words each, formed entirely from the following letters of the Spanish alphabet: a, e, u, b, d, g, j, n, r, z (List A) or i, o, c, f, h, l, m, p, s, t, v, y (List B). List C (Entire condition) contained 50 words formed from the entire alphabet, with the only criterion being that each word had to contain at least one letter from List A and at least one letter from List B.

This test is evaluated on a maximum of 30 points. Participants with scores equal to or below 23 would be considered cognitively deficient.

In this test, the subject is considered to have a good categorical evocation when he is able to evoke more than 16 animals in 1 minute and a good verbal fluency when he is able to evoke more than 19 words beginning with "p" in 3 minutes

This test is evaluated on a maximum of 30 points. Participants with scores equal to or below 23 would be considered cognitively deficient.

This cognitive test is evaluated on a maximum of 50 points. The optimal cut-off point for distinguishing mild cognitive impairment of the amnesiac type from subjective memory complaints is 37 points. The optimal cut-off point for Alzheimer's disease is 31 points.

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

All the information of the study, as well as its results, will be shared in scientific publications and conferences related to the research area. The information that is intended to be published in scientific journals includes: 1) Study Protocol, 2) Statistical Analysis, 3) Informed Consent Form, 4) Clinical Study Results.

Dedoncker J, Brunoni AR, Baeken C, Vanderhasselt MA. A Systematic Review and Meta-Analysis of the Effects of Transcranial Direct Current Stimulation (tDCS) Over the Dorsolateral Prefrontal Cortex in Healthy and Neuropsychiatric Samples: Influence of Stimulation Parameters. Brain Stimul. 2016 Jul-Aug;9(4):501-17. doi: 10.1016/j.brs.2016.04.006. Epub 2016 Apr 12.

Deldar Z, Rustamov N, Blanchette I, Piche M. Improving working memory and pain inhibition in older persons using transcranial direct current stimulation. Neurosci Res. 2019 Nov;148:19-27. doi: 10.1016/j.neures.2018.12.007. Epub 2019 Jan 4.

Galli G, Vadillo MA, Sirota M, Feurra M, Medvedeva A. A systematic review and meta-analysis of the effects of transcranial direct current stimulation (tDCS) on episodic memory. Brain Stimul. 2019 Mar-Apr;12(2):231-241. doi: 10.1016/j.brs.2018.11.008. Epub 2018 Nov 17.

Hill AT, Fitzgerald PB, Hoy KE. Effects of Anodal Transcranial Direct Current Stimulation on Working Memory: A Systematic Review and Meta-Analysis of Findings From Healthy and Neuropsychiatric Populations. Brain Stimul. 2016 Mar-Apr;9(2):197-208. doi: 10.1016/j.brs.2015.10.006. Epub 2015 Oct 23.

Huo L, Zheng Z, Huang J, Li R, Li J, Li J. Transcranial Direct Current Stimulation Enhances Episodic Memory in Healthy Older Adults by Modulating Retrieval-Specific Activation. Neural Plast. 2020 Dec 5;2020:8883046. doi: 10.1155/2020/8883046. eCollection 2020.

Nissim NR, O'Shea A, Indahlastari A, Kraft JN, von Mering O, Aksu S, Porges E, Cohen R, Woods AJ. Effects of Transcranial Direct Current Stimulation Paired With Cognitive Training on Functional Connectivity of the Working Memory Network in Older Adults. Front Aging Neurosci. 2019 Dec 16;11:340. doi: 10.3389/fnagi.2019.00340. eCollection 2019.

Perceval G, Martin AK, Copland DA, Laine M, Meinzer M. Multisession transcranial direct current stimulation facilitates verbal learning and memory consolidation in young and older adults. Brain Lang. 2020 Jun;205:104788. doi: 10.1016/j.bandl.2020.104788. Epub 2020 Mar 19.

Summers JJ, Kang N, Cauraugh JH. Does transcranial direct current stimulation enhance cognitive and motor functions in the ageing brain? A systematic review and meta- analysis. Ageing Res Rev. 2016 Jan;25:42-54. doi: 10.1016/j.arr.2015.11.004. Epub 2015 Nov 30.