Improvement of Apraxia With Augmented Reality: Influencing Pantomime of Tool Use via Holographic Cues

Background: Defective pantomime of tool use is a hall mark of limb apraxia. Contextual information has been demonstrated to improve tool use performance. Further, knowledge about the potential impact of technological aids such as augmented reality for patients with limb apraxia is still scarce.Objective: Since augmented reality offers a new way to provide contextual information, we applied it to pantomime of tool use. We hypothesize that the disturbed movement execution can be mitigated by holographic stimulation. If visual stimuli facilitate the access to the appropriate motor program in patients with apraxia, their performance should improve with increased saliency, i.e., should be better when supported by dynamic and holographic cues vs. static and screen-based cues.Methods: Twenty one stroke patients and 23 healthy control subjects were randomized to mime the use of five objects, presented in two Environments (Screen vs. Head Mounted Display, HMD) and two Modes (Static vs. Dynamic) resulting in four conditions (ScreenStat, ScreenDyn, HMDStat, HMDDyn), followed by a real tool demonstration. Pantomiming was analyzed by a scoring system using video recordings. Additionally, the sense of presence was assessed using a questionnaire.Results: Healthy control participants performed close to ceiling and significantly better than patients. Patients achieved significantly higher scores with holographic or dynamic cues. Remarkably, when their performance was supported by animated holographic cues (e.g., striking hammer), it did not differ significantly from real tool demonstration. As the sense of presence increases with animated holograms, so does the pantomiming.Conclusion: Patients' performance improved with visual stimuli of increasing saliency. Future assistive technology could be implemented upon this knowledge and thus, positively impact the rehabilitation process and a patient's autonomy.

Proposing a new short screening test for upper limb apraxia

Background Apraxia has a major impact on activities of daily living in stroke patients. The proper assessment and treatment of apraxia is important for maintaining a good quality of life. We developed a short evaluation test for upper limb apraxia. Patients and Methods The present Screening Test of Gestures for Stroke consists of 10 items for each verbal instruction and imitation. Each item includes three meaningless gestures, three meaningful gestures and four pantomimes. The Screening Test of Gestures for Stroke is scored based on a 3-point system: 10, 5 or 0 (maximum score: 200). The test took approximately 2–5 min to complete. We recruited 65 patients admitted to our hospital with left hemisphere stroke and 50 healthy subjects. Results The reliability of the Screening Test of Gestures for Stroke was as follows: the intraclass correlation coefficient of intra-rater reliability was 0.93 for both verbal instructions and imitations, and the intraclass correlation coefficient total scores for inter-rater reliability for verbal instructions and for imitations were 0.97 and 0.95, respectively. The alpha coefficient was ≥0.80. Conclusions The Screening Test of Gestures for Stroke is a reliable and valid bedside test that has a short assessment time, does not require special equipment and can evaluate upper limb apraxia in stroke patients from the acute to the chronic phase.

Characterising factors underlying praxis deficits in chronic left hemisphere stroke patients

Limb apraxia, a disorder of skilled action not consequent on primary motor or sensory deficits, has traditionally been defined according to errors patients make on neuropsychological tasks. Previous models of the disorder have failed to provide a unified account of patients’ deficits, due to heterogeneity in the patients and tasks used. In this study we implemented principal component analysis (PCA) to elucidate core factors of the disorder in a cohort of 41 unselected left hemisphere chronic stroke patients who were tested on a comprehensive and validated apraxia screen. Three principal components were identified: posture selection, semantic control and multi-demand sequencing. These were submitted to a lesion symptom mapping (VBCM) analysis in a subset of 24 patients, controlled for lesion volume, age and time post-stroke. Although the first component revealed no significant structural correlates, the second and third components were related to regions in the ‘ventro-dorsal’ and ‘ventral’ and ‘dorsal’ pathways, respectively. These results challenge the previously reported distinction between ideomotor and ideational deficits and highlight a significant role of common cognitive functions in the disorder, which include action selection, semantic retrieval, sequencing and response inhibition. Further research using this technique would help elucidate the cognitive processes underlying limb apraxia and their relationship with other cognitive disorders.