Freezing of Gait in Parkinson’s Disease: A Perceptual Cuase for a Motor Impairment?

While freezing of gait (FOG) is typically considered a motor impairment, the fact that it occurs more frequently in confined spaces suggests that perception of space might contribute to FOG. The present study evaluated how doorway size influenced characteristics of gait that might be indicative of freezing. Changes in spatiotemporal aspects of gait were evaluated while walking through three different-sized doorways (narrow (0.675 m wide X 2.1 m high), normal (0.9 m wide X 2.1 m high) and wide (1.8 m wide X 2.1 m high)) in three separate groups: 15 individuals with Parkinson’s disease confirmed to be experiencing FOG at the time of test; 16 non-FOG individuals with Parkinson’s disease and 16 healthy age-matched control participants. Results for step length indicated that the FOG group was most affected by the narrow doorway and was the only group whose step length was dependent on upcoming doorway size as indicated by a significant interaction of group by condition (F(4,88)=2.73, p\u3c0.034). Importantly, the FOG group also displayed increased within-trial variability of step length and step time, which was exaggerated as doorway size decreased (F(4,88)=2.99, p\u3c0.023). A significant interaction between group and condition for base of support measures indicated that the non-FOG participants were also affected by doorway size (similar to Parkinson’s disease FOG) but only in the narrow doorway condition. These results support the notion that some occurrences of freezing may be the result of an underlying perceptual mechanism that interferes with online movement planning

Evaluating the Contributors of Dynamic Flow to Freezing Gait in Parkinson’s Disease

Although visual cues can improve gait in Parkinson’s disease (PD), their underlying mechanism is poorly understood. Previous research suggests that cues contribute optical flow that is essential to elicit gait improvement. The present study manipulated how optic flow was provided, and how this might influence freezing of gait (FOG) in PD. Therefore, three groups; 15 PD FOG, 16 PD non-FOG, and 16 healthy controls were tested in 3 narrow doorway conditions; baseline (Narrow), ground lines (Ground), and laser (Laser). Step length indicated that the PD FOG group was only able to improve with ground lines, while the laser increased gait variability and double support time. These results suggest that optic flow in itself is not enough to elicit gait improvement in PD. When PD patients use visual cues, gait becomes less automatically controlled and hence preplanned conscious control may be an important factor contributing to gait improvement

The Relationship Between Motor Planning and Freezing of Gait in Parkinson’s Disease

Objective: To examine how a cued change in motor plan influences Parkinson’s disease (PD) patients with freezing of gait (FOG) (PD FOG; n=10), compared with those without FOG (PD non-FOG; n=10) and healthy controls (n=10). Methods: Participants walked through a doorway in three experimental conditions: no cue; cue before gait initiation; and cue after gait initiation. The light cue was presented at the end of the pathway and signified that individuals must walk to the cue, turn around and return to starting position. Results: Step-to-step variability (a known precursor to FOG) revealed a significant main effect of group (F2,27=32.83, p\u3c0.001), where PD FOG walked with greater step length variability than PD non-FOG and the control group. A significant interaction (F4,54=3.035, p=0.025) demonstrated that only the PD FOG group was most variable when the cue was present before gait initiation. Conclusion: This study concludes that motor planning deficits affect gait, specifically in individuals who experience FOG. This may have important implications for the design of therapeutic interventions in PD FOG

A Manipulation of Visual Feedback during Gait Training in Parkinson's Disease

Visual cues are known to improve gait in Parkinson's disease (PD); however, the contribution of optic flow continues to be disputed. This study manipulated transverse line cues during two gait training interventions (6 weeks). PD subjects (N = 42) were assigned to one of three groups: treadmill (TG), overground (OG), or control group (CG). Participants walked across lines placed on either treadmills or 16-meter carpets, respectively. The treadmill (TG) offered a reduced dynamic flow from the environment, while lines presented on the ground (OG) emphasized optic flow related to the participant's own displacement. Both interventions significantly improved (and maintained through retention period) step length, thus improving walking velocity. Only the OG improved in the TUG test, while only the TG showed hints of improving (and maintaining) motor symptoms. Since gait improvements were found in both training groups, we conclude that by reducing optic flow, gait benefits associated with visual cueing training can still be achieved

Screening for Parkinson’s Disease with Response Time Barriers: A Pilot Study

Background: Although significant response time deficits (both reaction time and movement time) have been identified in numerous studies of patients with Parkinson’s disease (PD), few attempts have been made to evaluate the use of these measures in screening for PD. Methods: Receiver operator characteristic curves were used to identify cutoff scores for a unitweighted composite of two choice response tasks in a sample of 40 patients and 40 healthy participants. These scores were then cross-validated in an independent sample of 20 patients and 20 healthy participants. Results: The unit-weighted movement time composite demonstrated high sensitivity (90%) and specificity (90%) in the identification of PD. Movement time was also significantly correlated (r = 0.59, p \u3c 0.025) with the motor score of the Unified Parkinson’s Disease Rating Scale (UPDRS). Conclusions: Measures of chronometric speed, assessed without the use of biomechanically complex movements, have a potential role in screening for PD. Furthermore, the significant correlation between movement time and UPDRS motor score suggests that movement time may be useful in the quantification of PD severity

Acute effects of aerobic exercise on cognitive function in individuals with Parkinson’s disease

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.neulet.2018.01.056 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Deficits in executive functions are highly prevalent in Parkinson’s disease (PD). Although chronic physical exercise has been shown to improve executive functions in PD, evidence of acute exercise effects is limited. This study aimed to evaluate the effects of an acute bout of exercise on cognitive processes underlying executive functions in PD. Twenty individuals with PD were assessed in both a Control and an Exercise conditions. In each condition, individuals started performing a simple and a choice reaction time (RT) task. Subsequently, participants were asked to sit on a cycle ergometer (Control) or cycle (Exercise) for 20 min in counterbalanced order. Participants were asked to repeat both reaction time tasks after 15-min rest period in both conditions. While no differences were found in simple RT, participants showed faster choice RT post Exercise as well as Control conditions (p = .012). Participants had slower choice RT for target stimulus compared to non-target stimuli irrespective of time or experimental condition (p < .001). There was no change in accuracy following experimental conditions. Results suggest that individuals with PD may not respond behaviourally to a single bout of exercise. The lack of selective effects of exercise on cognition suggests that practice effects may have influenced previous research. Future studies should assess whether neurophysiological changes might occur after an acute bout of exercise in PD