Optimizing tDCS to Improve Dual Task Gait and Balance

NCT ID: NCT04295798

Last Updated: 2025-01-30

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 29 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2020-02-10
• Study Completion Date: 2023-03-02

Brief Summary

The objective of this study is to determine the acute effects of single sessions of optimized tDCS, conventional tDCS, and sham stimulation on dual task standing and walking in older adults who are free of overt disease yet who present with poor baseline dual task performance.

Detailed Description

Standing and walking are almost always completed in unison with other cognitive tasks such as talking, reading or making decisions. The ability to perform this important type of "dual tasking" is critical to daily activities and dependent upon one's capacity to effectively activate appropriate brain networks that include the left dorsolateral prefrontal cortex (dlPFC). Transcranial direct current stimulation (tDCS) is a safe, noninvasive technology that can selectively modulate brain excitability (i.e., the likelihood of activation) by passing low-level currents between electrodes placed upon the scalp. We have demonstrated through a series of studies that a single, 20-minute exposure of 'conventional' tDCS targeting the left dlPFC-administered via two large sponge electrodes-reduces dual task costs to metrics of standing postural control and gait, when tested immediately following stimulation. Still, we and others have also observed relatively high between-subject variability in the effects of this conventional bipolar form of tDCS. We contend that this variability in effectiveness arises in part from relatively diffuse and unspecific current flow when using large sponge electrodes, in combination with individual variability in head and brain anatomy that significantly alters current flow and the generated electric field in the target brain region.

In this project, we will 1) apply recent advances in tDCS modeling and administration to model the electric fields generated by conventional tDCS in older adults using their individual structural brain MRIs, and 2) develop and test an multi-channel tDCS montage designed to optimize current flow to the left dlPFC (i.e., 'optimized' tDCS). Our Specific Aim is to examine the immediate after-effects of conventional tDCS, optimized tDCS, and sham stimulation on dual task standing and walking in older adults. Our study population will be older men and women without overt disease or illness, yet with poor baseline dual task performance defined as a dual task cost (i.e., reduction) to gait speed of at least 10% induced by simultaneously performing a serial subtraction task when walking. We hypothesize that across participants, the effect of conventional tDCS on dual task standing and walking performance will correlate with a specific component of the electric field generated over the left dlPFC target. We also hypothesize that optimized tDCS will induce A) greater effects on dual task standing and walking performance as compared to conventional tDCS and sham stimulation, and B) these effects will be more consistent across individuals as compared to conventional tDCS.

This project will provide important insights into tDCS "dosage" that will enable us and many other researchers to better understand, control, and optimize this form of noninvasive brain stimulation to individual head and brain anatomy. It is also expected to demonstrate that optimized tDCS, as compared to the conventional approach, significantly improves the size and consistency of observed benefits to dual task standing and walking in vulnerable older adults.

Conditions

Aging

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: QUADRUPLE

Study Groups

Conventional tDCS

One 20-minute session of active tDCS using two 35 cm2 sponge electrodes targeting the left dlPFC.

Group Type: EXPERIMENTAL

Conventional tDCS

Intervention Type: DEVICE

The anode will be placed over F3 and the cathode over the contralateral supraorbital margin. At the beginning of stimulation, the current will be increased from 0.1 mA, in 0.1 mA increments over 60 seconds, up to a maximum of 1.8 mA. At the end of each session, current will be automatically ramped down to 0.0 mA over a 60 second period.

Optimized tDCS

One 20-minute session of active tDCS using eight gel electrodes with placement and current parameters optimized to the cohort targeting the left dlPFC.

Group Type: EXPERIMENTAL

Optimized tDCS

Intervention Type: DEVICE

This intervention will utilize eight gel electrodes with placement and current parameters optimized to the cohort, with the goal of generating an average nE over the left dlPFC of the same size as the one delivered by a conventional montage using sponges. The direct current delivered by any one electrode will however never exceed 2.0 mA; the total amount of current from all electrodes will not exceed 4 mA. Each 20- minute session will begin and end with a 60-second ramp up/down of current amplitude to maximize comfort.

Conventional sham

One 20-minute session of inactive sham tDCS delivered via two sponge electrodes for a short period of time before it is ramped down to zero for the remainder of the session.

Group Type: SHAM_COMPARATOR

Conventional Sham

Intervention Type: DEVICE

Conventional sham will be used to maximize blinding of conventional sponge-based stimulation. The same sponge placement, ramp-up procedure, and session duration described above will be used; however, current will be automatically ramped down 60 seconds after ramp-up.

Optimized Sham

One 20-minute session of active sham in which the Stimweaver optimization algorithm will be used with the objective of creating a null electric field on the target left dlPFC with the constraint that some gel electrodes deliver low-level currents that still induce cutaneous sensations.

Group Type: SHAM_COMPARATOR

Optimized Sham

Intervention Type: DEVICE

An active sham will be used in which very low-level currents (0.5 mA max) are transferred between the same electrodes used in the active condition throughout the entire 20-minute session. This intervention will be optimized to deliver currents designed to not significantly influence their cortical tissue, but still mimic the cutaneous sensations induced by tDCS. We have shown that this active sham effectively blinds participants and operators to stimulation condition and does not affect functional outcomes.

Interventions

Conventional tDCS

The anode will be placed over F3 and the cathode over the contralateral supraorbital margin. At the beginning of stimulation, the current will be increased from 0.1 mA, in 0.1 mA increments over 60 seconds, up to a maximum of 1.8 mA. At the end of each session, current will be automatically ramped down to 0.0 mA over a 60 second period.

Intervention Type: DEVICE

Optimized tDCS

This intervention will utilize eight gel electrodes with placement and current parameters optimized to the cohort, with the goal of generating an average nE over the left dlPFC of the same size as the one delivered by a conventional montage using sponges. The direct current delivered by any one electrode will however never exceed 2.0 mA; the total amount of current from all electrodes will not exceed 4 mA. Each 20- minute session will begin and end with a 60-second ramp up/down of current amplitude to maximize comfort.

Intervention Type: DEVICE

Conventional Sham

Conventional sham will be used to maximize blinding of conventional sponge-based stimulation. The same sponge placement, ramp-up procedure, and session duration described above will be used; however, current will be automatically ramped down 60 seconds after ramp-up.

Intervention Type: DEVICE

Optimized Sham

An active sham will be used in which very low-level currents (0.5 mA max) are transferred between the same electrodes used in the active condition throughout the entire 20-minute session. This intervention will be optimized to deliver currents designed to not significantly influence their cortical tissue, but still mimic the cutaneous sensations induced by tDCS. We have shown that this active sham effectively blinds participants and operators to stimulation condition and does not affect functional outcomes.

Intervention Type: DEVICE

Eligibility Criteria

Inclusion Criteria

• Men and women aged 65-85 years
• Poor dual task performance, defined as a preferred gait speed that is >10% slower when walking and simultaneously performing verbalized serial subtractions (i.e., dual tasking), as compared to walking normally (i.e. single tasking)

Exclusion Criteria

• Unwillingness to cooperate or participate in the study protocol
• An inability to walk or stand for 30 continuous seconds without an assistive device
• A diagnosis of a gait disorder, Parkinson's disease, Alzheimer's disease or dementia, multiple sclerosis, previous stroke or other neurodegenerative disorder
• Self-report of acute illness, injury or other unstable medical condition; Any report of severe lower-extremity arthritis or pain, physician-diagnosis of peripheral neuropathy, or other peripheral neuromuscular disease that may confound the effects of tDCS on gait or postural control
• Use of antipsychotics, anti-seizure, benzodiazepines, or other neuroactive medications
• Severe depression defined by a Geriatric Depression Scale score greater than 11;
• Any report or physician-diagnosis of schizophrenia, bipolar disorder or other psychiatric illness
• Contraindications to MRI or tDCS, including reported seizure within the past two years, use of neuro-active drugs, the risk of metal objects anywhere in the body, self-reported presence of specific implanted medical devices (e.g., deep brain stimulator, medication infusion pump, cochlear implant, pacemaker, etc.), or the presence of any active dermatological condition, such as eczema, on the scalp

• Minimum Eligible Age: 65 Years
• Maximum Eligible Age: 85 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Hebrew SeniorLife

OTHER

Sponsor Role: lead

Responsible Party

Brad Manor

Associate Scientist

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Brad Manor, PhD

Role: PRINCIPAL_INVESTIGATOR

Hebrew SeniorLife

Locations

Hebrew Rehabilitation Center

Roslindale, Massachusetts, United States

Countries

United States

Provided Documents

Document Type: Study Protocol

View Document

Document Type: Statistical Analysis Plan

View Document

Document Type: Informed Consent Form

View Document

Other Identifiers

2019-23

Identifier Type: -

Identifier Source: org_study_id