BackgroundWalking is a complex cognitive motor task that is commonly completed while performing another task such as talking or making decisions. Gait assessments performed under normal and “dual-task” walking conditions thus provide important insights into health. Such assessments, however, are limited primarily to laboratory-based settings.ObjectiveThe objective of our study was to create and test a smartphone-based assessment of normal and dual-task walking for use in nonlaboratory settings.MethodsWe created an iPhone app that used the phone’s motion sensors to record movements during walking under normal conditions and while performing a serial-subtraction dual task, with the phone placed in the user’s pants pocket. The app provided the user with multimedia instructions before and during the assessment. Acquired data were automatically uploaded to a cloud-based server for offline analyses. A total of 14 healthy adults completed 2 laboratory visits separated by 1 week. On each visit, they used the app to complete three 45-second trials each of normal and dual-task walking. Kinematic data were collected with the app and a gold-standard–instrumented GAITRite mat. Participants also used the app to complete normal and dual-task walking trials within their homes on 3 separate days. Within laboratory-based trials, GAITRite-derived heel strikes and toe-offs of the phone-side leg aligned with smartphone acceleration extrema, following filtering and rotation to the earth coordinate system. We derived stride times—a clinically meaningful metric of locomotor control—from GAITRite and app data, for all strides occurring over the GAITRite mat. We calculated stride times and the dual-task cost to the average stride time (ie, percentage change from normal to dual-task conditions) from both measurement devices. We calculated similar metrics from home-based app data. For these trials, periods of potential turning were identified via custom-developed algorithms and omitted from stride-time analyses.ResultsAcross all detected strides in the laboratory, stride times derived from the app and GAITRite mat were highly correlated (P<.001, r2=.98). These correlations were independent of walking condition and pocket tightness. App- and GAITRite-derived stride-time dual-task costs were also highly correlated (P<.001, r2=.95). The error of app-derived stride times (mean 16.9, SD 9.0 ms) was unaffected by the magnitude of stride time, walking condition, or pocket tightness. For both normal and dual-task trials, average stride times derived from app walking trials demonstrated excellent test-retest reliability within and between both laboratory and home-based assessments (intraclass correlation coefficient range .82-.94).ConclusionsThe iPhone app we created enabled valid and reliable assessment of stride timing—with the smartphone in the pocket—during both normal and dual-task walking and within both laboratory and nonlaboratory environments. Additional work is warranted to expand the functionality of this tool to older adults and other pa...

Alzheimer's disease (AD) is an irreversible, progressive brain disorder that can cause dementia (Alzheimer's disease-related dementia, ADRD) with growing cognitive disability and vast physical, emotional, and financial pressures not only on the patients but also on caregivers and families. Loss of memory is an early and very debilitating symptom in AD patients and a relevant predictor of disease progression. Data from rodents, as well as human studies, suggest that dysregulation of specific brain oscillations, particularly in the hippocampus, is linked to memory deficits. Animal and human studies demonstrate that non-invasive brain stimulation (NIBS) in the form of transcranial alternating current stimulation (tACS) allows to reliably and safely interact with ongoing oscillatory patterns in the brain in specific frequencies. We developed a protocol for patient-tailored home-based tACS with an instruction program to train a caregiver to deliver daily sessions of tACS that can be remotely monitored by the study team. We provide a discussion of the neurobiological rationale to modulate oscillations and a description of the study protocol. Data of two patients with ADRD who have completed this protocol illustrate the feasibility of the approach and provide pilot evidence on the safety of the remotely-monitored, caregiver-administered, home-based tACS intervention. These findings encourage the pursuit of a large, adequately powered, randomized controlled trial of home-based tACS for memory dysfunction in ADRD.

Objective Among older adults, the ability to stand or walk while performing cognitive tasks (ie, dual‐tasking) requires coordinated activation of several brain networks. In this multicenter, double‐blinded, randomized, and sham‐controlled study, we examined the effects of modulating the excitability of the left dorsolateral prefrontal cortex (L‐DLPFC) and the primary sensorimotor cortex (SM1) on dual‐task performance “costs” to standing and walking. Methods Fifty‐seven older adults without overt illness or disease completed 4 separate study visits during which they received 20 minutes of transcranial direct current stimulation (tDCS) optimized to facilitate the excitability of the L‐DLPFC and SM1 simultaneously, or each region separately, or neither region (sham). Before and immediately after stimulation, participants completed a dual‐task paradigm in which they were asked to stand and walk with and without concurrent performance of a serial‐subtraction task. Results tDCS simultaneously targeting the L‐DLPFC and SM1, as well as tDCS targeting the L‐DLPFC alone, mitigated dual‐task costs to standing and walking to a greater extent than tDCS targeting SM1 alone or sham (p < 0.02). Blinding efficacy was excellent and participant subjective belief in the type of stimulation received (real or sham) did not contribute to the observed functional benefits of tDCS. Interpretation These results demonstrate that in older adults, dual‐task decrements may be amenable to change and implicate L‐DPFC excitability as a modifiable component of the control system that enables dual‐task standing and walking. tDCS may be used to improve resilience and the ability of older results to walk and stand under challenging conditions, potentially enhancing everyday functioning and reducing fall risks. ANN NEUROL 2021;90:428–439

Major depressive disorder (MDD) is a worldwide cause of disability in older age, especially during the covid pandemic. Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that has shown encouraging efficacy for treatment of depression. Here, we investigate the feasibility of an innovative protocol where tDCS is administered within the homes of older adults with MDD (patient participants) with the help of a study companion (i.e. caregiver). We further analyze the feasibility of a remotely-hosted training program that provides the knowledge and skills to administer tDCS at home, without requiring them to visit the lab. We also employed a newly developed multi-channel tDCS system with real-time monitoring designed to guarantee the safety and efficacy of home-based tDCS. Patient participants underwent a total of 37 home-based tDCS sessions distributed over 12 weeks. The protocol consisted of three phases each lasting four weeks: an acute phase, containing 28 home-based tDCS sessions, a taper phase containing nine home-based tDCS sessions, and a follow up phase, with no stimulation sessions. We found that the home-based, remotely-supervised, study companion administered, multi-channel tDCS protocol for older adults with MDD was feasible and safe. Further, the study introduces a novel training program for remote instruction of study companions in the administration of tDCS. Future research is required to determine the translatability of these findings to a larger sample.Clinical Trial Registration:https://clinicaltrials.gov/ct2/show/NCT04799405?term=NCT04799405&amp;draw=2&amp;rank=1, identifier NCT04799405.

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Background Parkinson disease (PD) is a common movement disorder. Patients with PD have multiple gait impairments that result in an increased risk of falls and diminished quality of life. Therefore, gait measurement is important for the management of PD. Objective We previously developed a smartphone-based dual-task gait assessment that was validated in healthy adults. The aim of this study was to test the validity of this gait assessment in people with PD, and to examine the association between app-derived gait metrics and the clinical and functional characteristics of PD. Methods Fifty-two participants with clinically diagnosed PD completed assessments of walking, Movement Disorder Society Unified Parkinson Disease Rating Scale III (UPDRS III), Montreal Cognitive Assessment (MoCA), Hamilton Anxiety (HAM-A), and Hamilton Depression (HAM-D) rating scale tests. Participants followed multimedia instructions provided by the app to complete two 20-meter trials each of walking normally (single task) and walking while performing a serial subtraction dual task (dual task). Gait data were simultaneously collected with the app and gold-standard wearable motion sensors. Stride times and stride time variability were derived from the acceleration and angular velocity signal acquired from the internal motion sensor of the phone and from the wearable sensor system. Results High correlations were observed between the stride time and stride time variability derived from the app and from the gold-standard system (r=0.98-0.99, P<.001), revealing excellent validity of the app-based gait assessment in PD. Compared with those from the single-task condition, the stride time (F1,103=14.1, P<.001) and stride time variability (F1,103=6.8, P=.008) in the dual-task condition were significantly greater. Participants who walked with greater stride time variability exhibited a greater UPDRS III total score (single task: β=.39, P<.001; dual task: β=.37, P=.01), HAM-A (single-task: β=.49, P=.007; dual-task: β=.48, P=.009), and HAM-D (single task: β=.44, P=.01; dual task: β=.49, P=.009). Moreover, those with greater dual-task stride time variability (β=.48, P=.001) or dual-task cost of stride time variability (β=.44, P=.004) exhibited lower MoCA scores. Conclusions A smartphone-based gait assessment can be used to provide meaningful metrics of single- and dual-task gait that are associated with disease severity and functional outcomes in individuals with PD.

Objective Symptomatic head trauma associated with American‐style football (ASF) has been linked to brain pathology, along with physical and mental distress in later life. However, the longer‐term effects of such trauma on objective metrics of cognitive–motor function remain poorly understood. We hypothesized that ASF‐related symptomatic head trauma would predict worse gait performance, particularly during dual task conditions (ie, walking while performing an additional cognitive task), in later life. Methods Sixty‐six retired professional ASF players aged 29 to 75 years completed a health and wellness questionnaire. They also completed a validated smartphone‐based assessment in their own homes, during which gait was monitored while they walked normally and while they performed a verbalized serial‐subtraction cognitive task. Results Participants who reported more symptomatic head trauma, defined as the total number of impacts to the head or neck followed by concussion‐related symptoms, exhibited greater dual task cost (ie, percentage increase) to stride time variability (ie, the coefficient of variation of mean stride time). Those who reported ≥1 hit followed by loss of consciousness, compared to those who did not, also exhibited greater dual task costs to this metric. Relationships between reported trauma and dual task costs were independent of age, body mass index, National Football League career duration, and history of musculoskeletal surgery. Symptomatic head trauma was not correlated with average stride times in either walking condition. Interpretation Remote, smartphone‐based assessments of dual task walking may be utilized to capture meaningful data sensitive to the long‐term impact of symptomatic head trauma in former professional ASF players and other contact sport athletes. ANN NEUROL 2020;87:75–83

Dual task walking assessments provide valuable insights into cognitive-motor function in aging. To date, such assessments have been limited primarily to laboratory-based settings. We thus created a smartphone App utilizing multi-media instructions and the phone’s motion sensors to record movements during normal and dual task walking, with the phone placed in the user’s pants pocket. Thirty younger and older adults completed two lab visits, during which walking data were simultaneously acquired by the App and the GAITRite mat. Participants also completed App-based assessments in their homes on three separate days. Across all detected strides in laboratory trials, gait metrics derived from the App correlated closely with those derived from the GAITRite mat (r2>0.96). Across trials, gait metrics demonstrated excellent test-retest reliability, both within and between laboratory visits and home-based assessments (ICC: 0.79–0.90). Remote, smartphone-based dual task walking assessments may therefore be feasible for relatively healthy younger and older adults.