Optimal visuotactile integration for velocity discrimination of self-hand movements

Illusory hand movements can be elicited by a textured disk or a visual pattern rotating under one's hand, while proprioceptive inputs convey immobility information (Blanchard C, Roll R, Roll JP, Kavounoudias A. PLoS One 8: e62475, 2013). Here, we investigated whether visuotactile integration can optimize velocity discrimination of illusory hand movements in line with Bayesian predictions. We induced illusory movements in 15 volunteers by visual and/or tactile stimulation delivered at six angular velocities. Participants had to compare hand illusion velocities with a 5°/s hand reference movement in an alternative forced choice paradigm. Results showed that the discrimination threshold decreased in the visuotactile condition compared with unimodal (visual or tactile) conditions, reflecting better bimodal discrimination. The perceptual strength (gain) of the illusions also increased: the stimulation required to give rise to a 5°/s illusory movement was slower in the visuotactile condition compared with each of the two unimodal conditions. The maximum likelihood estimation model satisfactorily predicted the improved discrimination threshold but not the increase in gain. When we added a zero-centered prior, reflecting immobility information, the Bayesian model did actually predict the gain increase but systematically overestimated it. Interestingly, the predicted gains better fit the visuotactile performances when a proprioceptive noise was generated by covibrating antagonist wrist muscles. These findings show that kinesthetic information of visual and tactile origins is optimally integrated to improve velocity discrimination of self-hand movements. However, a Bayesian model alone could not fully describe the illusory phenomenon pointing to the crucial importance of the omnipresent muscle proprioceptive cues with respect to other sensory cues for kinesthesia.

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Oculomotor inhibition covaries with conscious detection

Saccadic eye movements occur frequently even during attempted fixation, but they halt momentarily when a new stimulus appears. Here, we demonstrate that this rapid, involuntary "oculomotor freezing" reflex is yoked to fluctuations in explicit visual perception. Human observers reported the presence or absence of a brief visual stimulus while we recorded microsaccades, small spontaneous eye movements. We found that microsaccades were reflexively inhibited if and only if the observer reported seeing the stimulus, even when none was present. By applying a novel Bayesian classification technique to patterns of microsaccades on individual trials, we were able to decode the reported state of perception more accurately than the state of the stimulus (present vs. absent). Moreover, explicit perceptual sensitivity and the oculomotor reflex were both susceptible to orientation-specific adaptation. The adaptation effects suggest that the freezing reflex is mediated by signals processed in the visual cortex before reaching oculomotor control centers rather than relying on a direct subcortical route, as some previous research has suggested. We conclude that the reflexive inhibition of microsaccades immediately and inadvertently reveals when the observer becomes aware of a change in the environment. By providing an objective measure of conscious perceptual detection that does not require explicit reports, this finding opens doors to clinical applications and further investigations of perceptual awareness.

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Identifying candidates for targeted gait rehabilitation after stroke: better prediction through biomechanics-informed characterization

Walking speed has been used to predict the efficacy of gait training; however, poststroke motor impairments are heterogeneous and different biomechanical strategies may underlie the same walking speed. Identif...

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Evaluation of upper extremity neurorehabilitation using technology: a European Delphi consensus study within the EU COST Action Network on Robotics for Neurorehabilitation

The need for cost-effective neurorehabilitation is driving investment into technologies for patient assessment and treatment. Translation of these technologies into clinical practice is limited by a paucity of...

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Quantifying dimensions of physical behavior in chronic pain conditions

Chronic pain, defined as persistent or recurrent pain lasting longer than 3 months, is a frequent condition affecting an important percent of population worldwide. Pain chronicity can be caused by many differe...

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Use of mobile device accelerometry to enhance evaluation of postural instability in Parkinson’s disease

Publication date: Available online 23 September 2016
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Sarah J. Ozinga, Susan M. Linder, Jay L. Alberts
ObjectiveTo determine the accuracy of inertial measurement unit data from a mobile device using the mobile device relative to posturography to quantify postural stability in individuals with Parkinson's disease (PD).DesignCriterion standard.SettingMotor control laboratory at Cleveland Clinic.ParticipantsFourteen mild to moderate individuals with PD and 14 healthy age-matched community dwelling controls completed the project.InterventionsNot applicable.Main Outcome MeasuresCenter of mass (COM) acceleration measures were compared between the mobile device and NeuroCom force platform to determine accuracy of mobile device measurements during performance of the Sensory Organization Test (SOT). Analyses examined test-retest reliability for both systems and sensitivity of: 1) the Equilibrium Score from the SOT and 2) COM acceleration measures from the force platform and mobile device to quantify postural stability across populations.ResultsMetrics of COM acceleration from inertial measurement unit data and NeuroCom force platform were significantly correlated across balance conditions and groups (Pearson's r ranged from 0.35 to 0.97). The SOT Equilibrium Scores failed to discriminate individuals with PD and controls. However, the multi-planar measures of COM acceleration from the mobile device exhibited good to excellent reliability across SOT conditions and were able to discriminate individuals with PD and controls in conditions with the greatest balance demands.ConclusionsMetrics employing medial-lateral movement produce a more sensitive outcome than the Equilibrium Score in identifying postural instability associated with PD. Overall, the output from the mobile device provides an accurate and reliable method of rapidly quantifying balance in individuals with PD. The portable and affordable nature of a mobile device with the application make it ideally suited to utilize biomechanical data to aid in clinical decision-making.



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The effectiveness of aquatic exercise in improving lower limb strength in musculoskeletal conditions: a systematic review and meta-analysis

Publication date: Available online 22 September 2016
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Sophie Heywood, Jodie McClelland, Benjamin Mentiplay, Paula Geigle, Ann Rahmann, Ross Clark
ObjectiveTo investigate the effectiveness of aquatic exercise in improving lower limb strength in people with musculoskeletal conditions.Data SourcesA systematic search utilized five databases including MEDLINE, Cumulative Index to Nursing and Allied Health Literature, Embase, SPORTdiscus and The Cochrane Library.Study SelectionRandomized controlled trials evaluating aquatic exercise with a resistance training component for adults with musculoskeletal conditions compared with no intervention or land-based exercise were identified. 15 studies from the initial yield of 1214 met these criteria.Data ExtractionData related to participant demographics, study design and methods, intervention and outcomes including numerical means and SD were extracted independently by two reviewers.Data Synthesis9 of the 15 studies were of high quality, scoring at least six on the Physiotherapy Evidence Database Scale. Limited consideration of the prescription of resistance in the aquatic exercise and application of resistance training principles existed. Low or very low quality evidence indicates there was no difference in average effect between aquatic exercise and no exercise in improving hip abductor strength (SMD 0.28; 95%CI -0.04,0.59), knee extensor strength (SMD 0.18; 95%CI -0.03,0.40), knee flexor strength (SMD 0.13; 95%CI -0.20,0.45) or lower limb endurance (SMD 0.35; 95%CI -0.06,0.77). Low quality evidence indicates no difference in average effect between aquatic and land exercise for knee extensor (SMD -0.24; 95%CI -0.49,0.02) or flexor strength (SMD -0.15 ; 95%CI -0.53, 0.22).ConclusionsIt is likely that the inadequate application of resistance in water is a significant contributor to the limited effectiveness of aquatic exercise interventions in improving hip and knee muscle strength in people with musculoskeletal conditions. Future research is needed to quantify resistance with aquatic exercises and to determine if utilizing opportunities for greater resistance in aquatic rehabilitation as well as appropriate resistance training principles can be more effective in improving muscle strength.



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Correlates of perceived ankle instability in healthy individuals aged 8-101 years

Publication date: Available online 22 September 2016
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Jennifer Baldwin, Marnee McKay, Claire Hiller, Elizabeth J. Nightingale, Niamh Moloney, Joshua Burns
ObjectiveTo provide reference data for the Cumberland Ankle Instability Tool (CAIT) and investigate the prevalence and correlates of perceived ankle instability in a large healthy population.DesignCross-sectional observational study.SettingUniversity laboratory.ParticipantsSelf-reported healthy individuals (n=900; age range 8-101 years, stratified by age and gender) from the 1000 Norms Project.InterventionsNot applicable.Main Outcome MeasuresParticipants completed the CAIT (18-101 years) or CAIT-Youth (8-17 years). Socio-demographic factors, anthropometric measures, hypermobility, foot alignment, toes strength, lower limb alignment and ankle strength and range of motion were analysed.ResultsAmong 900 individuals aged 8-101 years, 23% (n=203) had bilateral and 8% (n=73) had unilateral perceived ankle instability. The odds of bilateral ankle instability were 2.6 (95%CI 1.7-3.8, p<.001) times higher for females; decreased by 2% (95%CI 1-3%, p=.001) for each year of increasing age, increased by 3% (95%CI 0-6%, p=.041) for each degree of ankle dorsiflexion tightness, and increased by 4% (95%CI 2-6%, p<.001) for each centimetre of increased waist circumference.ConclusionsPerceived ankle instability was common with almost a quarter of the sample reporting bilateral instability. Females, younger age, increased abdominal adiposity and decreased ankle dorsiflexion range of motion were independently associated with perceived ankle instability.



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Post-Traumatic Hydrocephalus as a Confounding Influence on Brain Injury Rehabilitation: Incidence, Clinical Characteristics and Outcomes

Publication date: Available online 23 September 2016
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Alan H. Weintraub, Donald J. Gerber, Robert G. Kowalski
ObjectiveTo describe incidence, clinical characteristics, complications, and outcomes in post-traumatic hydrocephalus (PTH) following traumatic brain injury (TBI) for patients treated in an inpatient rehabilitation program.DesignCohort study with retrospective comparative analysisSettingInpatient rehabilitation hospitalParticipantsAll patients admitted for TBI from 2009 to 2013 diagnosed with PTH, defined as ventriculomegaly, delayed clinical recovery discordant with injury severity, hydrocephalus symptoms, or positive lumbar puncture results.InterventionsNoneMain Outcome MeasuresPrimary measures were incidence of PTH, patient and injury characteristics. Secondary measures included frequency and timing of ventriculoperitoneal (VP) shunt, related complications, emergence from and duration of post-traumatic amnesia (PTA), Rancho Los Amigos Scale (RLAS) score and functional independence measure (FIM^TM), at rehabilitation admission and discharge.ResultsOf 701 TBI patients admitted, 59 (8%) were diagnosed with PTH. Of these, median age was 25 years, with 73% male. At initial presentation, 52 (88%) didn't follow commands. Fifty-two (90%) PTH patients had a VP shunt placed. Median time from injury to shunt placement was 69 days (range, 9-366). Seven (12%) PTH patients experienced post-surgical seizures, 3 (6%) had shunt infection and 7 (12%) shunt malfunction. Thirty six (61%) PTH patients emerged from PTA during rehabilitation. Median total FIM^TM score at rehabilitation admission was 20 (range, 18-76), and at discharge was 43 (range, 18-118). Injury severity predicted outcome at rehabilitation admission, while shunt timing predicted outcome at rehabilitation discharge.ConclusionsIncidence of PTH was observed in 8% of TBI patients in inpatient rehabilitation. Earlier shunting predicted improved outcome during rehabilitation. Future studies should prospectively examine clinical decision rules, type and timing of intervention and the co-effectiveness of rehabilitation treatment on outcomes.



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Clinical value of the Integrated Pulmonary Index® during sedation for interventional upper GI-endoscopy: A randomized, prospective tri-center study

The Integrated Pulmonary Index® (IPI) is a mathematically-determined factor based on parameters of capnography and pulse oximetry, which should enable sensitive detection of impaired respiratory function. Aim was to investigate whether an additional measurement of the IPI during sedation for interventional endoscopy, compared to standard monitoring alone, allows a reduction of sedation-related respiratory depression.

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