Synchronization of Neurophysiological and Biomechanical Data in a Real-Time Virtual Gait Analysis System (GRAIL): A Proof-of-Principle Study

The investigation of gait and its neuronal correlates under more ecologically valid conditions as well as real-time feedback visualization is becoming increasingly important in neuro-motor rehabilitation research. The Gait Real-time Analysis Interactive Lab (GRAIL) offers advanced opportunities for gait and gait-related research by creating more naturalistic yet controlled environments through immersive virtual reality. Investigating the neuronal aspects of gait requires parallel recording of brain activity, such as through mobile electroencephalography (EEG) and/or mobile functional near-infrared spectroscopy (fNIRS), which must be synchronized with the kinetic and /or kinematic data recorded while walking. This proof-of-concept study outlines the required setup by use of the lab streaming layer (LSL) ecosystem for real-time, simultaneous data collection of two independently operating multi-channel EEG and fNIRS measurement devices and gait kinetics. In this context, a customized approach using a photodiode to synchronize the systems is described. This study demonstrates the achievable temporal accuracy of synchronous data acquisition of neurophysiological and kinematic and kinetic data collection in the GRAIL. By using event-related cerebral hemodynamic activity and visually evoked potentials during a start-to-go task and a checkerboard test, we were able to confirm that our measurement system can replicate known physiological phenomena with latencies in the millisecond range and relate neurophysiological and kinetic data to each other with sufficient accuracy.

Distracting tasks have persisting effects on young and older drivers' braking performance

It is well established that car driving performance suffers when the driver concurrently engages in a distracting activity, such as talking on a cell phone. The present study investigates whether the effects of driver distraction are short-lived, or rather persist for some time. Age-related differences are evaluated as well. Sixty-three young and 61 older adults were tested in a driving simulator. They were asked to follow a lead car that drove at a constant speed, and to concurrently engage in a pseudorandom sequence of distracting tasks (typing, reasoning, memorizing). When the lead car braked, participants had to brake as well to prevent a collision. The stimulus onset asynchrony between the braking task and the last preceding distraction was 11.49 ± 1.99 s. Each person was tested once in a multitasking condition (as described above), and once in a control condition without distracting tasks. Outcome measures quantified distance keeping and lane keeping while participants braked to the lead car. We found that braking responses differed significantly between conditions; this difference could be interpreted as a combination of performance deficits and compensatory strategies in the multitasking condition compared to the control condition. We also found significant differences between age groups, which could be interpreted similarly. Differences between age groups were less pronounced in the multitasking than in the control condition. All observed effects were associated with participants' executive functioning. Our findings confirm that distractions have an impact on braking responses, and they document for the first time that this impact can persist for about 11.5 s. We attribute this persistence to a task set effect, and discuss the practical relevance of our findings.

Benefits of Higher Cardiovascular and Motor Coordinative Fitness on Driving Behavior Are Mediated by Cognitive Functioning: A Path Analysis

Driving is an important skill for older adults to maintain an independent lifestyle, and to preserve the quality of life. However, the ability to drive safely in older adults can be compromised by age-related cognitive decline. Performing an additional task during driving (e.g., adjusting the radio) increases cognitive demands and thus might additionally impair driving performance. Cognitive functioning has been shown to be positively related to physical activity/fitness such as cardiovascular and motor coordinative fitness. As such, a higher fitness level might be associated with higher cognitive resources and may therefore benefit driving performance under dual-task conditions. For the first time, the present study investigated whether this association of physical fitness and cognitive functioning causes an indirect relationship between physical fitness and dual-task driving performance through cognitive functions. Data from 120 healthy older adults (age: 69.56 ± 3.62, 53 female) were analyzed. Participants completed tests on cardiovascular fitness (cardiorespiratory capacity), motor coordinative fitness (composite score: static balance, psychomotor speed, bimanual dexterity), and cognitive functions (updating, inhibition, shifting, cognitive processing speed). Further, they performed a virtual car driving scenario where they additionally engaged in cognitively demanding tasks that were modeled after typical real-life activities during driving (typing or reasoning). Structural equation modeling (path analysis) was used to investigate whether cardiovascular and motor coordinative fitness were indirectly associated with lane keeping (i.e., variability in lateral position) and speed control (i.e., average velocity) while dual-task driving via cognitive functions. Both cardiovascular and motor coordinative fitness demonstrated the hypothesized indirect effects on dual-task driving. Motor coordinative fitness showed a significant indirect effect on lane keeping, while cardiovascular fitness demonstrated a trend-level indirect effect on speed control. Moreover, both fitness domains were positively related to different cognitive functions (processing speed and/or updating), and cognitive functions (updating or inhibition), in turn, were related to dual-task driving. These findings indicate that cognitive benefits associated with higher fitness may facilitate driving performance. Given that driving with lower cognitive capacity can result in serious consequences, this study emphasizes the importance for older adults to engage in a physically active lifestyle as it might serve as a preventive measure for driving safety.

Neurophysiological correlates of age differences in driving behavior during concurrent subtask performance

Driving is a complex cognitive-motor task that requires the continuous integration of multisensory information, cognitive processes, and motor actions. With higher age, driving becomes increasingly challenging as a result of naturally declining neurophysiological resources. Performing additional subtasks, such as conversations with passengers or interactions with in-vehicle devices (e.g., adjusting the radio), may further challenge neurocognitive resources that are required to maintain driving performance. Based on declining brain physiological resources and inferior neurocognitive functioning, older adults (OA) may show higher brain activation and larger performance decrements than younger adults (YA) when engaging in additional subtasks during driving. Age differences, however, may further vary for different neurocognitive task demands, such that driving performance of OA might be particularly affected by certain subtasks. In this study, we hence investigated the brain functional correlates of age differences in driving behavior during concurrent subtask performance in YA and OA. Our final sample consisted of thirty younger (21.80 ± 1.73y, 15 female) and thirty older (69.43 ± 3.30y, 12 female) regular drivers that drove along a typical rural road (25 - 30 min) in a driving simulator and performed three different concurrent subtasks that were presented auditorily or visually: typing a 3-digit number (TYPE), comparing traffic news and gas station prices (working memory, WM), and stating arguments (ARG). We measured variability in lateral car position, velocity, and following distance to a frontal lead car as the standard deviation from 0 to 15 s after subtask onset. Brain activity was continuously recorded using functional near-infrared spectroscopy over the dorsolateral prefrontal cortex. Both YA and OA particularly varied in their lateral position during TYPE with a more pronounced effect in OA. For YA, in contrast, ARG led to higher variability in velocity compared to TYPE and WM, whereas OA showed no task-specific differences. Substantiating our behavioral findings, OA revealed the largest brain functional response to TYPE, while YA demonstrated a very distinct activation during ARG and smaller hemodynamic responses to TYPE and WM. Brain activity in the DLPFC was, overall, not significantly, but small to moderately related to certain behavioral performance parameters (mainly lateral position). We conclude that both OA and YA are vulnerable to distractive subtasks while driving. Age differences, however, seem to largely depend on neurocognitive task demands. OA may be at higher risk for accidents when performing visuo-motor subtasks (e.g., interacting with navigational systems) during driving while YA may be more (cognitively) distracted when talking to passengers.