Presentation of multiple task instructional sets impacts auditory Stroop performance during dual task locomotion.

The auditory Stroop is a modification of the classic Stroop paradigm commonly used in dual-task research when the motor task requires the visual system. Despite its use, there are gaps in our understanding of this tool. For example, in visual/auditory Stroop paradigms, neutral cues irrelevant to the required response, which theoretically cause less interference/facilitation, are used to elucidate effects of visual/auditory demands on neural processes. Specifically, in auditory Stroop paradigms the use and choice of neutral cue words is inconsistent. To address these gaps, we instrumented participants with kinematic markers and a digital microphone and asked them to respond to auditory Stroop cues and neutral cue words consisting of either one or two syllables, while simultaneously performing an unobstructed locomotor task. Two blocks of trials were collected. In one block, participants had prior knowledge that either an auditory Stroop or a neutral word stimulus would be presented (Known); a second block presented both types of cognitive cues in a random order to participants (Mixed). We observed main effects of cognitive task (neutral, incongruent, congruent) and instructional set (Known, Mixed) on response times, but not on center of mass velocity. Also, more time was required to verbally respond to an incongruent compared to congruent or neutral task across all conditions, and neutral task words with one syllable resulted in longer response times compared to two syllable neutral words. We recommend that researchers include neutral cues when using the auditory Stroop test and to carefully consider their neutral word choice.

Exploring the cognitive demands required for young adults to adjust online obstacle avoidance strategies.

Humans integrate visual information about their surrounding environment to properly adapt their locomotion to step over or around obstacles in their path. We know that cognition aids in the execution of locomotion and in complex maneuvers such as obstacle avoidance. However, the role of the cognitive system in performing online adjustments to an obstacle avoidance strategy during locomotion has not yet been elucidated. Nineteen young adults instrumented with kinematic markers were asked to step over or circumvent an obstacle to the left or right. In half of these trials, participants were required to adjust this strategy when cued by LED lights two steps prior to obstacle crossing. In 75% of trials, a cognitive task was simultaneously presented (incongruent or congruent auditory Stroop cue, or neutral cue). Center of mass position and velocity was estimated and gait metrics (eg. step length) were calculated to quantify how individuals performed this last-minute direction change and determine how these responses changed when simultaneously performing a cognitive task. Results showed statistically shorter crossing steps, where the trailing limb was placed further from the leading edge and the lead limb was placed closer to the trailing edge when responding to the auditory Stroop task. Performing these avoidance strategy changes also decreased cognitive task performance. Our findings suggest that visually integrating a new stepping pattern to cross an obstacle is a complex locomotor maneuver, and requires the aid of the cognitive system to be performed effectively in a young adult population.

Visual cue spatial context affects performance of anticipatory postural adjustments.

Past research indicates that anticipatory postural adjustment (APA) errors may be due to the incorrect selection of responses to visual stimuli. In the current study we used the Simon task as a methodological tool to challenge the response selection stage of processing by presenting visual cues with conflicting spatial context; in this case generating a step response to a left pointing arrow which appears to the participant's right side or vice versa. We expected greater mediolateral APA errors, delayed APA and step onset times, and greater lateral CoP displacement prior to stepping for visual cues with incongruent spatial contexts compared to cues with congruent. Thirteen healthy young adults completed step initiation trials (n = 40) from a force platform while whole-body kinematic motion was tracked. Participants were presented with arrows pointing to the left or right, indicating to step with the left or right limb, respectively. These arrows were presented on the same side as the desired step direction (congruent) or the opposite side (incongruent). Results revealed that incongruent trials resulted in significantly more incidences of mediolateral APA errors and greater mediolateral CoP deviations during the APA compared to congruent visual cue context trials. No effects were observed for the temporal outcomes, suggesting that young adults can maintain temporal execution of steps despite these motor control errors. This study demonstrates that the spatial context of visual information significantly impacts the success of response selection processes during step initiation, furthering our knowledge of how humans integrate visual information to initiate whole body movement.

High-Intensity Interval vs. Moderate-Intensity Continuous Training in Parkinson's Disease: A Randomized Trial.

Exercise training is recommended to improve quality of life in those living with Parkinson's Disease (PD); however, the optimal prescription to improve cardiorespiratory fitness and disease-related motor symptoms remains unknown. Twenty-nine participants with PD were randomly allocated to either 10-weeks of high-intensity interval training (HIIT) (n=15; 6 female) or moderate-intensity continuous training (MICT) (n=14; 5 female). The primary outcome was the change in maximal oxygen consumption (VO2peak). Secondary outcomes included changes in the Unified Parkinson's Disease Rating Scale (UPDRS) Part III motor score, Parkinson's Disease Fatigue Scale (PFS-16), resting and exercise cardiovascular measures, gait, balance, and knee extensor strength and fatigability. Exercise training increased VO2peak (main effect of time, P<0.01), with a clinically-meaningful difference in the change following HIIT vs. MICT (∆3.7±3.7 vs. 1.7±3.2 ml∙kg-1∙min-1, P=0.099). The UPDRS motor score improved over time (P<0.001) but without any differences between HIIT vs. MICT (∆-9.7±1.3 vs. -8.4±1.4, P=0.51). Self-reported subjective fatigue (PFS-16) decreased over time (P<0.01) but was similar between HIIT and MICT groups (P=0.6). Gait, balance, blood pressure, and heart rate were unchanged with training (all P>0.09). Knee extensor strength increased over time (P=0.03) but did not differ between HIIT vs. MICT (∆8.2±5.9 vs. 11.7±6.2 Nm, P=0.69). HIIT alone increased muscular endurance of the knee extensors during an isotonic task to failure (P=0.04). In participants with PD, HIIT and MICT both increased VO2peak and led to improvements in motor symptoms and perceived fatigue; HIIT may offer the potential for larger changes in VO2peak and reduced knee extensor fatigability.

Physiological and clinical responses to cycling 7850 km over 85 days in a physically active middle-aged man with idiopathic Parkinson's disease.

This case characterizes the clinical motor, perceived fatigue, gait and balance, cardiovascular, neuromuscular, and cardiopulmonary responses after cycling 7850 km over 85 days in a physically active 57-year-old male with idiopathic Parkinson's disease (PD). The participant cycled 73/85 days (86%); averaging 107.5 ± 48.9 km/day over 255.4 ± 108.8 min. Average cycling heart rate was 117 ± 11 bpm. The Unified Parkinson Disease Rating Scale (UPDRS) Part III motor score decreased from 46 to 26 (-44%), while the mean Parkinson Fatigue Scale (PFS-16) score decreased from 3.4 to 2.3 (-32%). Peak power output on a maximal aerobic exercise test increased from 326 to 357 W (+10%), while peak isotonic power of single-leg knee extension increased from 312 to 350 W (+12%). Maximal oxygen uptake following the trip was 53.1 mL/min/kg or 151% of predicted. Resting heart rate increased from 48 to 71 bpm (+48%). The systolic and diastolic blood pressure responses to a 2-min submaximal static handgrip exercise were near absent at baseline (∆2/∆2 mm Hg) but appeared normal post-trip (∆17/∆9 mm Hg). Gait and static balance measures were unchanged. This case report demonstrates the capacity for physiological and clinical adaptations to a high-volume, high-intensity cycling regiment in a physically active middle-aged male with PD.

The Role of Cognition When Executing an Online, Visually Evoked Adjustment to an Obstacle Circumvention Strategy.

We know that performing simultaneous cognitive tasks during locomotion results in reduced performance on either or both tasks, however the role of the cognitive system in the execution of last-minute changes to ongoing adaptive locomotor tasks is not fully understood. Nineteen participants were initially cued to circumvent to left, right, or step over an obstacle while an auditory cognitive task was simultaneously presented. In half of the trials, no change in avoidance strategy was required; in the remaining trials, participants were visually cued two steps in advance to execute a new circumvention strategy. Participants decreased gait velocity and increased cognitive task response times when executing changes in strategy, highlighting the important role the cognitive system plays in these complex tasks.

Visual Cues Promote Head First Strategies During Walking Turns in Individuals With Parkinson's Disease.

Anticipatory eye movement promotes cranio-caudal sequencing during walking turns. Clinical groups, such as Parkinson's disease (PD), do not produce anticipatory eye movements, leading to increased risk of falls. Visual cues may promote anticipatory eye movement by guiding the eyes into the turn. This study examined if visual cues could train anticipatory eye movement. Ten neurotypical young adults and 6 adults with PD completed three blocks of walking trials. Trials were blocked by visual condition: non-cued baseline turns (5 trials), visually cued turns (10 trials), and non-cued post turns (5 trials). A Delsys Trigno (Delsys, Boston, MA) recorded horizontal saccades at 1024 Hz via electrooculography (EOG). Two Optotrak cameras (Northern Digital Inc., ON, Canada) captured body segment kinematics at 120 Hz. Initiation of segment rotation with respect to ipsilateral foot contact (IFC1) prior to the turn was calculated. Neurotypical young adults (NYA) produced typical cranio-caudal rotation sequences during walking turns. Eyes led (407 ms prior to IFC1), followed by the head (50 ms prior to IFC1), then trunk and pelvis. In contrast, PD produced no anticipatory eye or segment movement at baseline. During pre-trials the eyes moved 96 ms after IFC1 and segment movement was initiated by the pelvis followed by trunk and head segments. After visual cue training however, PD produced anticipatory eye movements 161 ms prior to IFC1, followed by the head 88 ms following IFC1 but ahead of trunk and pelvis onset. These results suggest visual cues assist in producing cranio-caudal control during walking turns in PD.