Walking through Apertures in Individuals with Stroke

Trainability of affordance judgments in right and left hemisphere stroke patients

Whenever we are confronted with action opportunities in everyday life, e.g., when passing an opening, we rely on our ability to precisely estimate our own bodily capabilities in relation to the environmental conditions. So-called affordance judgments can be affected after brain damage. Previous studies with healthy adults showed that such judgments appeared to be trainable within one session. In the current study, we examined whether stroke patients with either right brain damage (n = 30) or left brain damage (n = 30) may similarly profit from training in an aperture task. Further, the role of neuropsychological deficits in trainability was investigated. In the administered task, stroke patients decided whether their hand would fit into a presented opening with varying horizontal width (Aperture Task). During one training session, patients were asked to try to fit their hand into the opening and received feedback on their decisions. We analyzed accuracy and the detection theory parameters perceptual sensitivity and judgment tendency. Both patients with right brain damage and patients with left brain damage showed improved performance during training as well as post training. High variability with differential profiles of trainability was revealed in these patients. Patients with impaired performance in a visuo-spatial or motor-cognitive task appeared to profit considerably from the target-driven action phase with feedback, but the performance increase in judgments did not last when the action was withdrawn. Future studies applying lesion analysis with a larger sample may shed further light on the dissociation in the trainability of affordance judgments observed in patients with versus without visuo-spatial or motor-cognitive deficits.

Approaching Process in Walking through an Aperture for Individuals with Stroke

Muroi et al. show that individuals with stroke have improved collision avoidance behavior when passing through an aperture while entering from the paretic-side of the body. However, the underlying mechanism remains unknown. We reanalyzed Muroi et al.'s data to reveal how individuals with stroke walk through an aperture by examining changes in walking velocity and behavioral complexity (i.e., sample entropy, an index of (ir)regularity of time series, regarded lower entropy as more regular and less complex) by focusing on the approaching process. The results showed that individuals with stroke reduced their walking velocity and behavioral complexity before passing through the narrow aperture when approaching from the paretic side. We interpreted that the improved obstacle avoidance when penetrating from the paretic side may be due to careful body rotation and adjusting the walking velocity in advance.

Training for walking through an opening improves collision avoidance behavior in subacute patients with stroke: a randomized controlled trial

PURPOSE

Paretic side collisions frequently occur in stroke patients, especially while walking through narrow spaces. We determined whether training for walking through an opening (T-WTO) while entering from the paretic side would improve collision avoidance behavior and prevent falls after 6 months.

MATERIALS AND METHODS

Thirty-eight adults with moderate-to-mild hemiparetic gait after stroke who were hospitalized in a rehabilitation setting were randomly allocated to the T-WTO (n = 20) or regular rehabilitation (R-Control; n = 18) program. Both groups received five sessions of 40 min per week, for three weeks total. T-WTO included walking through openings of various widths while rotating with the paretic side in front, and R-Control involved normal walking without body rotation. Obstacle avoidance ability, 10-m walking test, timed Up and Go test, Berg Balance Scale, Activities-specific Balance Confidence, the perceptual judgment of passability, and fall incidence were assessed.

RESULTS

Collision rate and time to passage of the opening in obstacle avoidance task significantly improved in the T-WTO group compared with those in the R-Control group. Contrast, T-WTO did not lead to significant improvements in other outcomes.

CONCLUSIONS

T-WTO improved efficiency and safety in managing subacute stroke patients. Such training could improve patient outcomes/safety because of the paretic body side during walking.

CLINICAL TRIAL REGISTRATION NO.

R000038375 UMIN000033926.

Pathophysiological and motor factors associated with collision avoidance behavior in individuals with stroke

BACKGROUND

High collision rates and frequency of entering the opening from non-paretic sides are associated with collision in individuals with stroke.

OBJECTIVE

To identify factors associated with collision avoidance behavior when individuals with stroke walked through narrow openings.

METHODS

Participants with subacute or chronic stroke walked through a narrow opening and had to avoid colliding with obstacles. Multiple regression analyses were conducted with pathophysiology, motor function, and judgment ability as predictor variables; collision rate and frequency of entering the opening from non-paretic sides were outcome variables.

RESULTS

Sixty-one eligible individuals with stroke aged 63±12 years were enrolled. Thirty participants collided twice or more and 37 entered the opening from the non-paretic side. Higher collision occurrence was associated with slower Timed Up and Go tests and left-right sway (odds ratios, 1.2 and 5.6; 95% confidence intervals, 1.1-1.3 and 1.3-28.2; p = .008 and.025, respectively). Entering from non-paretic sides was associated with lesions in the thalamus, left-sided hemiplegia, and Brunnstrom stage 3 or lower (odds ratios, 6.6, 8.7, and 6.7; 95% confidence intervals, 1.3-52.5, 2.5-36.5, and 1.2-57.5; and p = .038,.001, and.048, respectively).

CONCLUSION

Walking ability is associated with avoiding obstacle collision, while pathophysiological characteristics and degree of paralysis are associated with a preference for which side of the body enters an opening first. Interventions to improve walking ability may improve collision avoidance. Avoidance behavior during intervention varies depending on the lesion position.

Walking through a narrow opening improves collision avoidance behavior in a patient with stroke and unilateral spatial neglect: an ABA single-case design

We investigated the effect of a 3-week intervention-wherein a patient with unilateral spatial neglect walks through a narrow opening while entering from the contralesional side-to improve walking ability or ADL. A 66-year-old man was diagnosed with right parietal subcortical hemorrhage. We used an ABA single-case design; period B was set as the intervention. The intervention improved the continuous walking distance and balance ability and decreased the number of collisions when walking through the narrow opening; however, it exerted minimal effect on ADL. Thus, the intervention may effectively improve continuous physical or spatial attention behavior, regardless of ADL improvement.

Walking through an aperture while penetrating from the paretic side improves safety managing the paretic side for individuals with stroke who had previous falls

BACKGROUND

Safety management of the paretic side of the body is critical for individuals with stroke. We previously reported that individuals with stroke who walk through an aperture while penetrating from the paretic side had fewer collisions with the frame of an aperture than did those penetrating from the non-paretic side. We observed spontaneous behavior of collision avoidance in our previous study; this study thus used penetration from the paretic and non-paretic sides as independent variables to confirm the usefulness of penetrating from the paretic side.

OBJECTIVE

This study aimed to (1) reconfirm whether walking through a narrow space while penetrating from the paretic side leads to reduced frequency of collision only for individuals with stroke with previous falls by manipulating the direction of penetration as independent variables and to (2) determine whether the behavioral or cognitive characteristics of passing through the aperture are observed in individuals with stroke who had previous falls.

METHODS

Individuals with stroke (12 with previous falls, 13 without) were required to walk through a narrow space while penetrating from the paretic and non-paretic sides. The collision rate and kinematic characteristics at the moment of crossing the aperture (body rotation angle, deviation of body's midpoint, and movement speed) were recorded as dependent variables. We also confirmed whether the participants expected collision after passing.

RESULTS

Individuals with stroke with previous falls were less likely to have a collision when penetrating from the paretic side. The stroke fall group was likely to experience more collisions because of deleterious changes in body rotation angle and movement speed in narrow apertures. Moreover, individuals with stroke have many unexpected collisions, but the decline in anticipatory ability was not unique to the stroke fall group.

CONCLUSIONS

Penetrating a narrow space from the paretic side improved safety management of the paretic side in patients with previous falls despite poor adjustment to narrow apertures. Penetrating a narrow space from the paretic side may make it easier to view and pay attention to the paretic side.

Is This Within Reach? Left but Not Right Brain Damage Affects Affordance Judgment Tendencies

The ability to judge accurately whether or not an action can be accomplished successfully is critical for selecting appropriate response options that enable adaptive behaviors. Such affordance judgments are thought to rely on the perceived fit between environmental properties and knowledge of one's current physical capabilities. Little, however, is currently known about the ability of individuals to judge their own affordances following a stroke, or about the underlying neural mechanisms involved. To address these issues, we employed a signal detection approach to investigate the impact of left or right hemisphere injuries on judgments of whether a visual object was located within reach while remaining still (i.e., reachability). Regarding perceptual sensitivity and accuracy in judging reachability, there were no significant group differences between healthy controls (N = 29), right brain damaged (RBD, N = 17) and left brain damaged stroke patients (LBD, N = 17). However, while healthy controls and RBD patients demonstrated a negative response criterion and thus overestimated their reach capability, LBD patients' average response criterion converged to zero, indicating no judgment tendency. Critically, the LBD group's judgment tendency pattern is consistent with previous findings in this same sample on an affordance judgment task that required estimating whether the hand can fit through apertures (Randerath et al., 2018). Lesion analysis suggests that this loss of judgment tendency may be associated with damage to the left insula, the left parietal and middle temporal lobe. Based on these results, we propose that damage to the left ventro-dorsal stream disrupts the retrieval and processing of a stable criterion, leading to stronger reliance on intact on-line body-perceptive processes computed within the preserved bilateral dorsal network.

The downsized hand in personal neglect

Introduction: Personal neglect (PN) refers to a form of hemi-inattention toward the contralesional body space and it usually occurs following a right brain lesion. Recent studies suggest that PN indicates a disorder of body representation. Specifically, patients with PN show difficulties in identifying differences between left and right hands and have an altered visuospatial body map, which is associated with disrupted mental body representations. However, the metric representation of the body, and in particular the hands, has not been systematically addressed in patients showing this form of neglect. Method: In the present study, we have investigated this representation by testing the perceived hands' width of 11 hemiplegic patients with right hemisphere cerebral lesions (5 with PN) and 12 healthy controls on a judgment of passability task. Patients and controls were asked to imagine inserting their hand (left and right) through a series of vertical apertures of different sizes and to judge whether their hand could fit through. Due to the heterogeneity of the data, both parametric and non-parametric approaches were used. Furthermore, additional single-case analyses were conducted. Results: Study findings showed that patients with PN showed a significant underestimation of the left hand compared with their right hand. In contrast, whilst the right hand was equally distorted in both patients' groups, the hemiplegic patients with no evidence of PN tended to perceive the affected hand as larger than their ipsilesional one. Conclusions: In line with the literature, our findings confirm an underlying distorted body representation following right brain damage. However, for the first time, we report both a quantitative and qualitative difference in impact of hemiplegia and PN on body representation of the contralesional body space.

How Does a Walker Pass Between Two People Standing in Different Configurations? Influence of Personal Space on Aperture Passing Methods

Most studies on aperture passability focus on aperture passing involving non-human physical objects. In this study, we examined experimentally how participants pass between two box-shaped frames and between the same frames, each with a human confederate in it, facing various directions. Seven configuration conditions were set up, six of which differed in terms of the human confederates’ sets of directions in the two frames: face-to-face, back-to-back, facing toward or away from the participants, facing leftward or rightward from the participants’ perspective, and the empty frames condition without human confederates. There were seven aperture-width conditions—50, 55, 60, 65, 70, 75, and 80 cm—and participants walked at their normal speed through the apertures. We found that the participants’ shoulder rotation angle in the face-to-face condition was significantly greater than that in the empty frames condition. Further, the participants preferred to rotate their shoulders counterclockwise when our confederates in the aperture faced leftward, and clockwise, when they faced rightward. These results suggest that people change their passing-through methods by considering the social nature of the aperture as well as its width.

Does it fit? - Impaired affordance perception after stroke

Affordance perception comprises the evaluation of whether our given bodily capabilities and properties of the environment allow particular actions. Typical impairments after left brain damage in motor cognition as well as after right brain damage in visuo-spatial abilities may affect the evaluation of whether interactions with objects are possible. Further it is unclear whether deficient motor function is accounted for when deciding upon action opportunities. For these purposes we developed a paradigm with two tasks that differ in their type of demands on affordance perception and tested it in healthy young adults (Randerath and Frey, 2016). Here, we applied one of these two tasks in stroke patients and age matched healthy participants. A sample of 34 stroke patients with either left (LBD) or right brain damage (RBD) and 29 healthy controls made decisions about whether their hands would fit through a defined horizontal aperture presented in various sizes, while they remained still. Data was analyzed using a detection theory approach and included criterion, perceptual sensitivity and diagnostic accuracy as dependent variables. In addition we applied modern voxel based lesion analyses to explore neural correlates. Compared to controls, both patient groups demonstrated lower perceptual sensitivity. As predicted, increased motor cognitive deficiencies after left brain damage and visuo-spatial deficits after right brain damage were associated with worse performance. Preliminary lesion analyses demonstrated that next to lesions in ventro-dorsal regions, damage in the cortex-claustrum-cingulate pathway may affect perceptual sensitivity. Results were similar for left and right brain damage suggesting a bilateral network. Accordingly, we propose that perceptual sensitivity for affordance based judgments is a capability depending on motor-cognitive and visuo-spatial processing, which frequently is deficient after left or right brain damage, respectively. Further research on diagnostics and training in affordance perception after brain damage is needed.