Investigating Different Frequencies of Transcranial Electrical Stimulations in Dementia Population

About 100 participants with either mild cognitive impairment (MCI) or a probable early or moderate dementia type excluding Parkinsonian dementia (as confirmed by their treating physician), will be recruited and tested over the course of this study.

Participants will have the option to choose to do the stimulation and cognitive exercise from home or at Riverview Health Centre. However, all assessments will be completed at Riverview Health Centre. One of the main limitations of human research is the small sample size as recruitment and enrollment of eligible participants especially in dementia population is a major challenge. Thus, a longitudinal study. Each participant will receive all 4 tES protocols in a randomized order while playing cognitive exercises:

1. Personalized gamma tACS

2. Personalized theta tACS

3. tDCS (zero frequency)

4. Sham tES The protocol for all tES treatments will be 4 weeks, 5 days/week (excluding weekends), two 30-min training sessions/day with 15 to 30 min break in between, all tutored either in-person or virtually. Participants will be assessed the week before each new treatment block, within a week of post-treatment and a month after the end of treatment block (follow-up). Between the different tES treatment protocols, 8-week to 20-week washout period will take place with no treatment. The time period for each participant to receive all 4 protocols will be around one year and a half depending on the duration of the washout period. After the participant completes all 4 protocols, there is one more treatment protocol where the participant will receive tACS at the personalized gamma over the regular placement of electrodes (left dorsolateral prefrontal cortex and the reference electrode on the contralateral supraorbital area) for the first 30-min training session and then over the precuneus (one electrode over Pz on the 10-20 EEG system and the other over the right deltoid muscle) during the second 30-min training session. Then the investigators will offer the treatment type (any of the above 5 experimental types) with the highest efficacy for each participant. In other words, the investigators will offer an optimized treatment after the one year and a half.

The eligibility criteria for enrolling individuals into this study are: 50 y<age<95 y, 5<MoCA<24.

Exclusion criteria are any of the followings:

• Being diagnosed with Parkinson's, Parkinsonian dementia, Huntington disease, speech significant aphasia and intellectual disability, major depression/anxiety, bipolar disorder, schizophrenia or any other major mood disorder.

• Having a History of epileptic seizures or epilepsy

• Inability to adequately communicate in English

• Impaired vision or hearing severe enough to impair performance in cognitive tests

• Current substance abuse disorder

• Currently participating in another therapeutic study for dementia

The global objective of the proposed study is to investigate the effects of different tES in improving the cognitive status of older adults with dementia, when paired simultaneously with cognitive training. The general objectives include the following:

1. Run a human research randomized and double-blind study to address the global objective of the study with statistical rigor.

2. Investigate the correlation of fNIRS outcomes with those of the primary outcome measures of the study in Objective 1 as well as its predictivity to the treatment at baseline.

3. Investigate the effects of different tES on EEG recordings as well as its predictivity to the treatment at baseline.

4. Investigate the effects of different tES on balance for older adults with cognitive impairment.

5. Investigate the correlation of EVestG outcomes with those of the primary outcome measures of the study in Objective 1 as well as its predictively to the treatment at baseline.

6. Disseminate the project results and design the next follow up project.