Dual-task Training in Older Adults

In order to functionally move through one's community, it is vital to be able to perform simultaneous motor and cognitive tasks (cognitive-motor dual-task). This allows us to talk to another person, scan the environment for oncoming traffic, and avoid objects that are in our path when walking. This even allows high level sporting participation, such as predicting an opponents' path when sprinting and cutting to score a goal. Unfortunately, aging is associated with increased difficulty in performing cognitive-motor tasks. A classical example is when older adults stop walking in order to talk to another person. Several studies have established that an increase in age is associated with increased cognitive resources required to perform normally automatic motor tasks. Deficits in cognitive-motor dual-task capabilities have been observed not only in older adults, but also in those with neuromuscular compromise due to factors such as stroke and Parkinson's, and even with altered cognition in mild cognitive impairment and Attention Deficit Disorder.

Although these early investigations suggest a relationship between physical and cognitive capabilities, little is known regarding the appropriate level of cognitive task difficulty that will result in improvements or delays in learning a motor task. Conflicting results are noted in the few studies that have investigated this line of research. Some support that a concurrent cognitive task provides a context that facilitates motor learning, while other show that cognitive load prevents individuals from fully learning the motor task . Further, there are very few studies that investigate the effect of cognitive load on the transfer of motor learning to new task conditions for weight-bearing activities. Early evidence suggests that generalizability of learning diminishes the further participants are from the initial task conditions. Interestingly, cognition has been suggested to play a vital role in motor learning, performance, and dual-task capability. Working memory capacity, or the process that allows the maintenance and manipulation of information over a short period of time, has been shown to strongly relate to the rate at which younger adults learn motor sequences, and moderately relate the motor learning of older adults. Executive function, or the properties of cognitive flexibility, problem-solving, and response maintenance, also plays a role in motor learning and performance. Decrements in executive function has been shown to precede mobility limitations, and might even predict gains in mobility from a physical intervention. Executive function may also predict a large portion of the variability when under the context of simultaneously having a cognitive load. There continues to be a lack of understanding of what cognitive capacity is required to perform simultaneous mobility and cognitive tasks with the least risk of injury, and what dose of intervention in both physical and cognitive realms are necessary to induce an improvement in function of both systems.

Purpose: To determine the impact an intervention using simultaneous cognitive and motor tasks on the capacity of healthy adults to improve in functional mobility and cognition.

Research Question: Does a cognitive-motor intervention impact functional mobility and cognition of healthy older adults?

Following obtaining consent from the subject, testing will take place three times a week for 8 weeks. Subjects are randomly assigned to one of each of the three groups: control group, simple cognitive group, or complex cognitive group.

Subjects will be informed that they are randomly assigned to one of three possible groups. Subjects will then be asked to perform either a visuomotor task only (control group), or a visuomotor task with a simultaneous cognitive task (simple cognitive group and complex cognitive group). The visuomotor task is the same regardless of group assignment. The difference in intervention between groups is based on the simultaneous task that the individual will perform: the control group will perform no cognitive task, the simple cognitive group will perform a task of counting a defined letter that appears on the screen, and the complex cognitive group will be assigned the task of counting two assigned letters that appear on the screen. The visuomotor task consists of performing a standing in-place march, lifting alternating knees to 60 degrees of hip flexion, eight cycles on each leg. A custom computer program displays a real-time video of the individual on the screen with an overlay of markers indicating computerized detection (Microsoft Kinect) of the knee joint. A prescribed marching rate is determined by an ellipse on the screen that prescribes the displacement (degrees of hip flexion) and rate of movement (speed) in which to move. Subjects will be allowed light touch for balance if required. One minute of seated rest will be provided between trials with the option of longer rest as needed. Video of the subject is saved in a de-identified format consisting of the view of the individual on the screen and the target task only during the duration of each individual trial. The cognitive task is displayed on the same screen as the motor task. Letters of different orientations and colors appear and disappear on the screen. Each of the 24 sessions will involve performing approximately 20 trials of the visuomotor and cognitive task (control group: visuomotor task only, intervention groups: visuomotor + cognitive task).

Additional details regarding the visuomotor and cognitive tasks are as follows. On the first day, 13th, and 24th days, subjects will perform 20 training trials at a medium speed of the marching task (training), followed by 5 trials of varying marching speeds (testing) by altering the speed (not the amplitude) of a target ellipse that moves on the screen. Then, subjects will be asked to perform one trial of each the simple and the complex cognitive tasks without performing the marching task (cognitive task only). On days 13, and 24 days, subjects will also perform the 5 testing trials under each of the other groups' cognitive task assignment (e.g. a subject assigned to the simple cognitive task group would first perform 5 training and 5 testing trials while performing the simple cognitive task, they would then perform 5 testing trials with the complex cognitive task followed by 5 trials while only performing the motor task). During all other days of the 24 interventions, subjects will perform 20 trials of the medium speed visuomotor task, performing only the cognitive task required of their assigned group.

Additionally, on the 1st,13th, and 24th day, the investigators will take height, weight, and use a scale that measures the participant's body fat percentage (by standing barefoot on the scale). Subjects will be asked to fill out questionnaires which will include information about medical, physical and social life, cognition, activity level, sleep quality and pain levels (see attached forms). Subjects will then be asked to undergo computerized testing of general cognitive function and perceived health via the NIH Toolbox Cognition Battery and PROMIS (via iPad app), and a paper-based assessment of cognition (Montreal Cognitive Assessment). During the NIH Toolbox Cognition Battery test, subjects will sit comfortably in a chair with their arm resting on a table and will perform four tests: the Flanker Inhibitory Control and Attention Test (FLCAT), The List Sorting Working memory Test (LSWMT), The Dimensional Change Card Sort Test (DCCST), and the Processing Speed Test (PST). The FLCAT, DCCST, and PST tests require the user to select an object on the screen using their finger as quickly as possible; the LSWMT will require no movement, but to recite objects of animals and fruits that appear on the screen of the iPad. The Subjects are free to skip any questions or tests that they would prefer not to answer or complete. A test of balance is performed asking the individual to stand on a pressure sensitive mat (Zeno Mat) to record foot pressures and amount of body sway. They will be asked to stand in place with their 1) eyes open, 2) eyes closed, and 3) performing a cognitive task while standing on each foot (single limb stance). Subjects will then be asked to perform a Timed Up and Go (TUG) test under conditions of performing a cognitive task (TUG Cognitive), and without a secondary task (TUG). The TUG test consists of moving as quickly as possible through standing from sitting, walking 3 meters, turning around, and returning three meters to return to the starting seated position. Each test is usually performed in under 30 seconds. Subjects will then be asked to perform a 10-meter walk test, where in the middle of the 8 meters of self-selected walking, they will walk over a pressure sensitive mat (ZenoMat) to determine properties of gait. The 10m walk test will be perform with and without a simultaneous cognitive task at a speed that they feel is normal for them, and then as quickly as they can walk safely.

On days 1, 2, 13, and 24, the investigators will use wireless electrodes with a disposable adhesive interface will be placed over the alcohol abraded skin of lower extremity muscles in order to collect surface electromyography. Following placement of electrodes subjects will be asked to perform three maximal volitional isometric contraction (MVIC) for each muscle. Each MVIC is achieved by the experimenter applying manual resistance in serial with a hand-held dynamometer at the distal most portion of the segment (leg) to which the muscle attaches. The subject is then provided with verbal encouragement to move the limb being tested in the primary direction of muscle movement (eg. For the quadriceps muscles, resistance is applied to the distal tibia at the level of just proximal to the malleoli during knee extension). Between each maximal effort, 1-min rest will be provided to prevent fatigue.