Previous work has used dual test measures to evaluate athletes with recent concussion. Our protocol is significant because we've created a shorter, cost efficient measure that permits simultaneous neuroimaging. If effective at eliciting greater dual task cost in athletes with concussion, our dual task screen measure will be applicable for use in a variety of clinical settings.
For a single condition lower extremity sub-task, place three yoga blocks in a horizontal position exactly 4.5 meters apart along an 18 meter walkway and firmly attach smart devices to both of the participant's ankles. Instruct the participant that they will have to walk as quickly as possible while stepping over the obstacles and quickly tap both accelerometers to start the test using a stopwatch to measure the time it takes the participant to complete the task. As the participant's heel strikes the ground, raw data will be generated that can be analyzed to assess the participant's gait characteristics.
At the end of the task, inform the participant of the time it took them to complete the task from their single motor condition. Then ask the participant to say as many words as they can that begin with a particular letter. For a dual lower extremity sub-task, after instructing the participant how to perform the task, tap both accelerometers to start the task and time the participant while they step over obstacles as quickly as possible while simultaneously stating as many words as possible that begin with a particular letter.
For a single upper extremity sub-task, use masking tape to mark a 1.5 meter distance from a wall and instruct the participant to stand behind the tape. Place a basket of tennis balls next to the participant and have the participant complete a wall toss with alternating hands for 30 seconds using a new ball from the basket for any balls they fail to catch. At the end of the task, ask the participant to sequentially subtract seven from a given number for 30 seconds.
For a dual upper extremity sub-task, have the participant perform the wall toss with alternating hands while sequentially subtracting seven from a given number for 30 seconds, selecting a new ball from the basket after any misses as necessary. To set up a neuroimaging compatible task, place yoga blocks in a vertical position to mark the start and end of a 15-meter walkway and place two yoga blocks in a horizontal position exactly five meters apart along the 15 meter walkway. Then mark a 1.5 meter distance away from a smooth wall surface.
Next, measure the participant's head circumference and place an appropriately sized fNIRS cap with pre-placed optodes and short channel detectors onto the participant's head. Turn on a dedicated acquisition laptop and connect the laptop to the fNIRS device WiFi network. In the fNIRS acquisition software, select the fNIRS device and perform a calibration to optimize the light intensity.
At the end of the calibration, check the optodes'signal levels which should be acceptable or excellent. To fix any optodes with a less than acceptable signal level, remove the optode from the cap and part the participant's hair to ensure a direct connection to the participant's scalp. To acquire lower extremity sub-task neuroimaging data, open the stimulus presentation software and select the lower extremity sub-task file.
Have the participant sit in a chair and click start to begin collecting baseline fNIRS data. Enter the subject ID, lower extremity, age, and sex into the popup window and click start experiment. Inform the participant that a quiet rest period is beginning and press the Space Bar to start a 60-second rest period.
At the end of the rest period, explain the lower extremity task schedule to the participant and press the Space Bar to start the first trial. After 15 randomized trials of the lower extremity sub-tasks have been performed, have the participant rest for another 60 seconds in the chair. At the end of the rest period, exit out of the sub-task file in the stimulus presentation software and stop the data acquisition in the fNIRS data acquisition software.
Then remove the accelerometers from the participant's ankles and use the software to perform the upper extremity analysis as demonstrated. At the end of the rest period, explain the upper extremity task schedule to the participant and press the Space Bar to start the first trial. In these representative analyses of three male participants, a slower gait speed, longer average step duration, and greater variability in step duration are observed during dual compared to single condition tasks.
In contrast, two of three participants showed no changes in the number of total steps or the average step length under single motor versus dual task conditions. Two out of three participants also generated fewer words during the dual cognitive task condition compared to the single task condition. All three male participants had a dual task motor cost with fewer successful catches observed during the dual task condition compared to the single motor condition.
Fewer correct subtractions during the dual task condition were also observed in two of the three participants compared to the single task condition. Here, a map of the placement of the 15 LED sources and 15 detectors on the participant's head can be observed. Use of the fNIRS cap during the lower and upper extremity sub-task trials allows measurement and comparison of the oxygenated hemoglobin levels produced by the participant during the dual and single motor sub-tasks.
During the neuroimaging compatible dual test screen, the most important thing to remember is to provide the participant with the correct instructions for the tasks and to ensure their comprehension. Because fNIRS only allows us to evaluate superficial cortical structures, our data may suggest that we should complete complimentary neuroimaging using something like fMRI to evaluate deeper brain structures.
