Aging Intervention for MCI Population: The AIM Pilot Study

The current study is a mechanistic study to evaluate working memory gains from application of transcranial direct current stimulation (tDCS) in older adults with mild cognitive impairments (MCI) compared to cognitively healthy control

The current study is a mechanistic study to evaluate working memory gains with transcranial direct current stimulation (tDCS) in older adults with mild cognitive impairments (MCI) compared to cognitively healthy control. This study is funded by a mentored career award (The University of Florida, Clinical and Translational Science Institute [CTSI] Pilot Award) and thus the mentors (Drs. Cohen, DeKosky, Woods, Fang) are listed as additional Principal Investigators in this study. The proposed study investigates the effects of acute (one-time) tDCS application on working memory gains (i.e., behavior and functional) by evaluating brain structure and cognitive function relationships. tDCS is a method of non-invasive brain stimulation that directly stimulates brain regions involved in active cognitive function and enhances neural plasticity when paired with a training task. A mechanistic, in-scanner, crossover design tDCS study (active and sham stimulation) with 2milliamps (mA) fixed dosing application will enroll 20 participants comprising 10 cognitively normal/healthy older adults and 10 older adults with MCI. The study will employ multi-modal neuroimaging (structural and functional data), person-specific computational models, and machine learning to elucidate acute tDCS effects on working memory. Change in cognitive function (i.e., working memory performance) will be quantified using working memory tasks and magnetic resonance imaging (MRI). The investigators will compare changes in working memory performance resulting from active tDCS versus sham tDCS during 2-back task compared to 0-back task. The investigators will test the following hypotheses: Acute tDCS will increase working memory performance during active tDCS and larger degree of brain atrophy seen in MCI patients will significantly decrease current intensity in stimulated brain regions. Acute tDCS will significantly increase functional connectivity within the working memory network during active tDCS but not sham. To date, no studies have examined acute tDCS application in MCI cohort and directly comparing results to cognitively healthy cohort. The present study will provide insight into mechanisms underlying tDCS application in MCI population for combating cognitive decline in a rapidly aging population in the United States. Information gathered from this study may guide future intervention strategies to combat cognitive decline and improve the quality of life of aging population.

Cognitive Aging, Brain Stimulation, functional MRI, Computational Modeling, Finite Element Method (FEM)

Participants will enroll in a randomized double-blinded crossover within subject study. Each participant will undergo two MRI sessions. Each MRI session will include either one active tDCS or one sham tDCS. The order of delivering active or sham tDCS first will be randomized. A washout period between active and sham tDCS will be set for at least two-weeks to ensure no after-effect from the first stimulation session will be carried over to the second session.

A blinding code will be entered into the stimulation device to initiate the randomized stimulation condition.

AA neuroConn MR-safe 1x1 tDCS stimulator will be used to apply 12 minutes of 2.0 mA electrical current, with 30 seconds ramps up and 30 seconds ramps down. The electrical current will be applied by using two carbon rubber electrodes (one anode, one cathode) with added ten20 conductive paste. The electrode+paste will be affixed on the participant's scalp over the frontal cortices at F3 and F4 location (EEG 10-20 system). Inflow of current (anode) will occur at F4 location, and outflow of current will occur at F3 (cathode).

Sham stimulation will be performed with the same 1x1 device. Participants will receive 2 mA of direct current stimulation for 30 seconds with 30 seconds ramps up and down. This provides the tingling and prickling sensation on the scalp associated with tDCS while prevent delivering sufficient current (12 minutes) to penetrate the skull and stimulate the brain. Prep in sham conditions will be identical to active stimulation conditions. For each stimulation condition (active, sham), each participant will perform three runs of N-back working memory task (baseline/pre-stimulation, during stimulation, and after/post-stimulation) as detailed below. Sham efficacy will be evaluated as a direct comparison in N-back performance and connectivity results in active group versus sham group.

A neuroConn MR-safe 1x1 tDCS stimulator will be used to apply 12 minutes of 2.0 mA electrical current, with 30 seconds ramps up and 30 seconds ramps down. The electrical current will be applied by using two carbon rubber electrodes (one anode, one cathode) with added ten20 conductive paste. The electrode+paste will be affixed on the participant's scalp over the frontal cortices at F3 and F4 location (EEG 10-20 system). Inflow of current (anode) will occur at F4 location, and outflow of current will occur at F3 (cathode).

Sham stimulation will be performed with the same 1x1 device. Participants will receive 2 mA of direct current stimulation for 30 seconds with 30 seconds ramps up and down. This provides the tingling and prickling sensation on the scalp associated with tDCS while prevent delivering sufficient current (12 minutes) to penetrate the skull and stimulate the brain. Prep in sham conditions will be identical to active stimulation conditions. For each stimulation condition (active, sham), each participant will perform three runs of N-back working memory task (baseline/pre-stimulation, during stimulation, and after/post-stimulation) as detailed below. Sham efficacy will be evaluated as a direct comparison in N-back performance and connectivity results in active group versus sham group.

N-back accuracy as working memory performance will be analyzed as a percent accuracy score on the 2-back and 0-back task.

12 minutes versus 24 minutes, 12 minutes versus 36 minutes, 24 minutes versus 36 minutes for each active stimulation and sham stimulation. Then at each time point comparing active versus sham stimulation, separated by at least two weeks.

Inclusion Criteria: Age 60-95 years Montreal Cognitive Assessment (MoCA) score 18 and above (scores will be adjusted for education) Able to receive electrical stimulation Ability to comprehend conversational voices Adequate motor capacity to operate computer mouse and click-button in-scanner Ability to participate in the intervention and attend training sessions Exclusion Criteria: Failure to provide informed consent Contraindications to MRI recording (e.g., any kind of ferrous metallic stents or ferrous metal objects in the body, heart valve prosthesis, or other metal implants, claustrophobia, neurostimulation system, defibrillator, pacemaker, or other implanted device) Left-handed, or left hand dominant History of neurological, seizures, and psychiatric disorders, traumatic brain injury, incidence of stroke involving large vessel Terminal illness with life expectancy less than 12 months, as determined by physician Brain tumor or any foreign body known or previously identified in brain Cancer in active treatment, besides skin cancer Currently on GABAergic or glutamatergic medications, or on calcium or sodium channel blockers, which alter or block the ability of tDCS to facilitate tissue excitability Unable to communicate because of severe hearing loss or speech disorder Severe sensory impairment Inability to communicate in English Severe visual impairment, which would preclude completion of the assessment and/or intervention No physical impairment precluding motor response or lying still for an hour in the scanner that could confound study findings