Concurrent validity and test-retest reliability of the Virtual Peg Insertion Test to quantify upper limb function in patients with chronic stroke.

BACKGROUND: Measuring arm and hand function of the affected side is vital in stroke rehabilitation. Therefore, the Virtual Peg Insertion Test (VPIT), an assessment combining virtual reality and haptic feedback during a goal-oriented task derived from the Nine Hole Peg Test (NHPT), was developed. This study aimed to evaluate (1) the concurrent validity of key outcome measures of the VPIT, namely the execution time and the number of dropped pegs, with the NHPT and Box and Block Test (BBT), and (2) the test-retest-reliability of these parameters together with the VPIT's additional kinetic and kinematic parameters in patients with chronic stroke. The three tests were administered on 31 chronic patients with stroke in one session (concurrent validity), and the VPIT was retested in a second session 3-7 days later (test-retest reliability). Spearman rank correlation coefficients (ρ) were calculated for assessing concurrent validity, and intraclass correlation coefficients (ICCs) were used to determine relative reliability. Bland-Altman plots were drawn and the smallest detectable difference (SDD) was calculated to examine absolute reliability. RESULTS: For the 31 included patients, 11 were able to perform the VPIT solely via use of their affected arm, whereas 20 patients also had to utilize support from their unaffected arm. For n = 31, the VPIT showed low correlations with the NHPT (ρ = 0.31 for time (Tex[s]); ρ = 0.21 for number of dropped pegs (Ndp)) and BBT (ρ = -0.23 for number of transported cubes (Ntc); ρ = -0.12 for number of dropped cubes (Ndc)). The test-retest reliability for the parameters Tex[s], mean grasping force (Fggo[N]), number of zero-crossings (Nzc[1/sgo/return) and mean collision force (Fcmean[N]) were good to high, with ICCs ranging from 0.83 to 0.94. Fair reliability could be found for Fgreturn (ICC = 0.75) and trajectory error (Etrajgo[cm]) (0.70). Poor reliability was measured for Etrajreturn[cm] (0.67) and Ndp (0.58). The SDDs were: Tex = 70.2 s, Ndp = 0.4 pegs; Fggo/return = 3.5/1.2 Newton; Nzc[1/s]go/return = 0.2/1.8 zero-crossings; Etrajgo/return = 0.5/0.8 cm; Fcmean = 0.7 Newton. CONCLUSIONS: The VPIT is a promising upper limb function assessment for patients with stroke requiring other components of upper limb motor performance than the NHPT and BBT. The high intra-subject variation indicated that it is a demanding test for this stroke sample, which necessitates a thorough introduction to this assessment. Once familiar, the VPIT provides more objective and comprehensive measurements of upper limb function than conventional, non-computerized hand assessments.

Detection of motor execution using a hybrid fNIRS-biosignal BCI: a feasibility study.

BACKGROUND: Brain-computer interfaces (BCIs) were recently recognized as a method to promote neuroplastic effects in motor rehabilitation. The core of a BCI is a decoding stage by which signals from the brain are classified into different brain-states. The goal of this paper was to test the feasibility of a single trial classifier to detect motor execution based on signals from cortical motor regions, measured by functional near-infrared spectroscopy (fNIRS), and the response of the autonomic nervous system. An approach that allowed for individually tuned classifier topologies was opted for. This promises to be a first step towards a novel form of active movement therapy that could be operated and controlled by paretic patients. METHODS: Seven healthy subjects performed repetitions of an isometric finger pinching task, while changes in oxy- and deoxyhemoglobin concentrations were measured in the contralateral primary motor cortex and ventral premotor cortex using fNIRS. Simultaneously, heart rate, breathing rate, blood pressure and skin conductance response were measured. Hidden Markov models (HMM) were used to classify between active isometric pinching phases and rest. The classification performance (accuracy, sensitivity and specificity) was assessed for two types of input data: (i) fNIRS-signals only and (ii) fNIRS- and biosignals combined. RESULTS: fNIRS data were classified with an average accuracy of 79.4%, which increased significantly to 88.5% when biosignals were also included (p=0.02). Comparable increases were observed for the sensitivity (from 78.3% to 87.2%, p=0.008) and specificity (from 80.5% to 89.9%, p=0.062). CONCLUSIONS: This study showed, for the first time, promising classification results with hemodynamic fNIRS data obtained from motor regions and simultaneously acquired biosignals. Combining fNIRS data with biosignals has a beneficial effect, opening new avenues for the development of brain-body-computer interfaces for rehabilitation applications. Further research is required to identify the contribution of each modality to the decoding capability of the subject's hemodynamic and physiological state.

Evaluation of upper limb function with digitizing tablet-based tests: reliability and discriminative validity in healthy persons and patients with neurological disorders.

PURPOSE: To evaluate discriminative validity, relative reliability and absolute reliability of four tablet-based tests for the evaluation of upper limb motor function in healthy persons and patients with neurological disorders. METHODS: Cross-sectional study in 54 participants: 29 patients with upper limb movement impairment due to a neurological condition recruited from an inpatient rehabilitation centre and 25 healthy persons. Accuracy, speed and path length were analysed for four tablet-based tests: "Spiral drawings," "Tapping," "Follow the dot" and "Trace a star." The area under the receiver operating characteristic curve (AUC) was used to evaluate discriminative validity. Relative reliability was analysed with the intra-class correlation coefficient (ICC), and absolute reliability by limits of agreement (LoA) and minimal detectable difference (MDD). RESULTS: All four tests showed excellent discriminative validity for the parameter accuracy (AUC 0.93-0.98). Tapping was the best test for discriminating patients from healthy persons. Test-retest reliability was good for accuracy in all tests (ICC = 0.76-0.88), but poor to moderate for speed and path length (ICC = 0.20-0.69). The MDD varied between 14% and 38%. Performance on the four tablet-based tests was stable between sessions, indicating that there was no learning effect. CONCLUSION: The parameter accuracy showed excellent discriminative validity and reliability in all four tablet-based tests. Discriminative validity was excellent for all three parameters in the Tapping test. In the other tasks speed showed good to poor reliability, while the reliability of path-length was poor in all tasks. Results were comparable for the dominant and non-dominant hand. Tablet-based tests have the advantage that patients can use them for self-monitoring of upper limb motor function.Implications for rehabilitationFour tablet-based tests for the assessment of upper limb motor function in patients with upper limb neurological dysfunction were evaluated: "Spiral drawings", "Tapping", "Follow the dot" and "Trace a star". The parameter accuracy in these four tests had excellent discriminative validity and good reliability.Patients can perform the tests independently at home for self-monitoring of progress. This may increase patients' motivation to exercise at home.The results can be sent to physicians, enabling the earlier detection of deterioration, which may require medical attention.

Context-specific grasp movement representation in macaque ventral premotor cortex.

Hand grasping requires the transformation of sensory signals to hand movements. Neurons in area F5 (ventral premotor cortex) represent specific grasp movements (e.g., precision grip) as well as object features like orientation, and are involved in movement preparation and execution. Here, we examined how F5 neurons represent context-dependent grasping actions in macaques. We used a delayed grasping task in which animals grasped a handle either with a power or a precision grip depending on context information. Additionally, object orientation was varied to investigate how visual object features are integrated with context information. In 420 neurons from two animals, object orientation and grip type were equally encoded during the instruction epoch (27% and 26% of all cells, respectively). While orientation representation dropped during movement execution, grip type representation increased (20% vs 43%). According to tuning onset and offset, we classified neurons as sensory, sensorimotor, or motor. Grip type tuning was predominantly sensorimotor (28%) or motor (25%), whereas orientation-tuned cells were mainly sensory (11%) or sensorimotor (15%) and often also represented grip type (86%). Conversely, only 44% of grip-type tuned cells were also orientation-tuned. Furthermore, we found marked differences in the incidence of preferred conditions (power vs precision grips and middle vs extreme orientations) and in the anatomical distribution of the various cell classes. These results reveal important differences in how grip type and object orientation is processed in F5 and suggest that anatomically and functionally separable cell classes collaborate to generate hand grasping commands.

Context-specific grasp movement representation in the macaque anterior intraparietal area.

To perform grasping movements, the hand is shaped according to the form of the target object and the intended manipulation, which in turn depends on the context of the action. The anterior intraparietal cortex (AIP) is strongly involved in the sensorimotor transformation of grasping movements, but the extent to which it encodes context-specific information for hand grasping is unclear. To explore this issue, we recorded 571 single-units in AIP of two macaques during a delayed grasping task, in which animals were instructed by an external context cue (LED) to perform power or precision grips on a handle that was presented in various orientations. While 55% of the recorded neurons encoded the object orientation from the cue epoch on, the number of cells encoding the grip type increased from 25% during the cue epoch to 58% during movement execution. Furthermore, a classification of cells according to the time of their tuning onset revealed differences in the function and anatomical location of early- versus late-tuned cells. In a cue separation task, when the object was presented first, neurons representing power or precision grips were activated simultaneously until the actual grip type was instructed. In contrast, when the grasp type instruction was presented before the object, type information was only weakly represented in AIP, but was strongly encoded after the grasp target was revealed. We conclude that AIP encodes context specific hand grasping movements to perceived objects, but in the absence of a grasp target, the encoding of context information is weak.

The Virtual Peg Insertion Test as an assessment of upper limb coordination in ARSACS patients: a pilot study.

OBJECTIVE: This paper introduces a novel assessment tool to provide clinicians with quantitative and more objective measures of upper limb coordination in patients suffering from Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS). The Virtual Peg Insertion Test (VPIT) involves manipulating an instrumented handle in order to move nine pegs into nine holes displayed in a virtual environment. The main outcome measures were the number of zero-crossings of the hand acceleration vector, as a measure of movement coordination and the total time required to complete the insertion of the nine pegs, as a measure of overall upper limb performance. RESULTS: 8\9 patients with ARSACS were able to complete five repetitions with the VPIT. Patients were found to be significantly less coordinated and slower than age-matched healthy subjects (p<0.01). Performance of ARSACS patients was positively correlated with the Nine-Hole Peg Test (r=0.85, p<0.01) and with age (r=0.93, p<0.01), indicative of the degenerative nature of the disease. CONCLUSION(S): This study presents preliminary results on the use of a robotics and virtual reality assessment tool with ARSACS patients. Results highlight its potential to assess impaired coordination and monitor its progression over time.

Assessment of upper limb motor function in patients with multiple sclerosis using the Virtual Peg Insertion Test: a pilot study.

Quantifying and tracking upper limb impairment is of key importance to the understanding of disease progress, establishing patient-tailored therapy protocols and for optimal care provision. This paper presents the results of a pilot study on the assessment of upper limb motor function in patients with multiple sclerosis (MS) with the Virtual Peg Insertion Test (VPIT). The test consists in a goal-directed reaching task using a commercial haptic display combined with an instrumented handle and virtual environment, and allows for the extraction of objective kinematic and dynamic parameters. Ten MS patients and eight age-matched healthy subjects performed five repetitions of the VPIT with their dominant and non-dominant hand. Upper limb movements were found to be significantly slower, less smooth and less straight compared to healthy controls, and the time to complete the VPIT was well correlated with the conventional Nine Hole Peg Test (r=0.658, p<0.01). Tremor in the range of 3-5 Hz could be detected and quantified using a frequency analysis in patients featuring intention tremor. These preliminary results illustrate the feasibility of using the VPIT with MS patients, and underline the potential of this test to evaluate upper limb motor function and discriminate characteristic MS related impairments.

Motor execution detection based on autonomic nervous system responses.

Triggered assistance has been shown to be a successful robotic strategy for provoking motor plasticity, probably because it requires neurologic patients' active participation to initiate a movement involving their impaired limb. Triggered assistance, however, requires sufficient residual motor control to activate the trigger and, thus, is not applicable to individuals with severe neurologic injuries. In these situations, brain and body-computer interfaces have emerged as promising solutions to control robotic devices. In this paper, we investigate the feasibility of a body-machine interface to detect motion execution only monitoring the autonomic nervous system (ANS) response. Four physiological signals were measured (blood pressure, breathing rate, skin conductance response and heart rate) during an isometric pinching task and used to train a classifier based on hidden Markov models. We performed an experiment with six healthy subjects to test the effectiveness of the classifier to detect rest and active pinching periods. The results showed that the movement execution can be accurately classified based only on peripheral autonomic signals, with an accuracy level of 84.5%, sensitivity of 83.8% and specificity of 85.2%. These results are encouraging to perform further research on the use of the ANS response in body-machine interfaces.

Effects of 2D/3D visual feedback and visuomotor collocation on motor performance in a Virtual Peg Insertion Test.

This paper evaluates the influence of three different types of visual feedback on the motor performance of healthy subjects during the repeated execution of a Virtual Peg Insertion Test developed for the assessment of sensorimotor function of arm and hand in neurologically impaired subjects. One test trial consists of the grasping and insertion of 9 pegs into 9 holes using a haptic display with instrumented grasping handle. Three groups performed 10 trials initially on three different setups (group 1 with standard 2D visual feedback, group 2 with 3D, and group 3 with collocated 3D visual feedback) followed by 10 more trials with the setup with 2D visual feedback. The total execution time and the mean collision force as well as the time and the collision force for 6 different movement phases were compared between groups and analyzed in function of the number of repetitions. Results showed significantly lower time to approach and align the visual cursor with the peg with the 2D setup over the first 10 trials compared to the two other groups, suggesting limitations of the 3D setup. Furthermore, a significant decrease of the total execution time was found in the first 10 trials for all groups. For the 10 following trials, only group 3 showed a significant decrease in the total execution time, suggesting that the learning did not transfer to the 2D setup for this group.

Upper limb assessment using a Virtual Peg Insertion Test.

This paper presents the initial evaluation of a Virtual Peg Insertion Test developed to assess sensorimotor functions of arm and hand using an instrumented tool, virtual reality and haptic feedback. Nine performance parameters derived from kinematic and kinetic data were selected and compared between two groups of healthy subjects performing the task with the dominant and non-dominant hand, as well as with a group of chronic stroke subjects suffering from different levels of upper limb impairment. Results showed significantly smaller grasping forces applied by the stroke subjects compared to the healthy subjects. The grasping force profiles suggest a poor coordination between position and grasping for the stroke subjects, and the collision forces with the virtual board were found to be indicative of sensory deficits. These preliminary results suggest that the analyzed parameters could be valid indicators of impairment.

Towards a BCI for sensorimotor training: initial results from simultaneous fNIRS and biosignal recordings.

This paper presents the concept and initial results of a novel approach for robot assisted sensorimotor training in stroke rehabilitation. It is based on a brain-body-robot interface (B(2)RI), combining both neural and physiological recordings, that detects the intention to perform a motor task. By directly including the injured brain into the therapy, we ultimately aim at providing a new method for severely impaired patients to engage in active movement therapy. In the present study, seven healthy subjects performed an isometric finger pinching task while functional near-infrared spectroscopy (fNIRS) signals from motor cortical areas and biosignals were recorded simultaneously. Results showed an insignificant increase in the blood pressure during the preparation period prior to motor execution. During the execution period, significant changes in oxy-and deoxyhemoglobin were found in the primary motor cortex, accompanied by an increase in blood pressure, respiration rate and galvanic skin response (GSR). Cortical measurements of premotor areas and heart rate revealed significant changes at the subject level with large inter-subject variability. The results presented here will serve as priors for the design of further studies to test the efficacy of the concept with stroke patients, and the found effects will provide a basis for the development of a classifier for a future B(2)RI.