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Raveh, E., Portnoy, S., & Friedman, J. (2018). Adding vibrotactile feedback to a myoelectric-controlled hand improves performance when online visual feedback is disturbed. Hum Mov Sci, 58, 32–40.
Abstract: We investigated whether adding vibrotactile feedback to a myoelectric-controlled hand, when visual feedback is disturbed, can improve performance during a functional test. For this purpose, able-bodied subjects, activating a myoelectric-controlled hand attached to their right hand performed the modified Box & Blocks test, grasping and manipulating wooden blocks over a partition. This was performed in 3 conditions, using a repeated-measures design: in full light, in a dark room where visual feedback was disturbed and no auditory feedback – one time with the addition of tactile feedback provided during object grasping and manipulation, and one time without any tactile feedback. The average time needed to transfer one block was measured, and an infrared camera was used to give information on the number of grasping errors during performance of the test. Our results show that when vibrotactile feedback was provided, performance time was reduced significantly, compared with when no vibrotactile feedback was available. Furthermore, the accuracy of grasping and manipulation was improved, reflected by significantly fewer errors during test performance. In conclusion, adding vibrotactile feedback to a myoelectric-controlled hand has positive effects on functional performance when visual feedback is disturbed. This may have applications to current myoelectric-controlled hands, as adding tactile feedback may help prosthesis users to improve their functional ability during daily life activities in different environments, particularly when limited visual feedback is available or desirable.
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Noy, L., Alon, U., & Friedman, J. (2015). Corrective jitter motion shows similar individual frequencies for the arm and the finger. Exp Brain Res, 233(4), 1307–1320.
Abstract: A characteristic of visuomotor tracking of non-regular oscillating stimuli are high-frequency jittery corrective motions, oscillating around the tracked stimuli. However, the properties of these corrective jitter responses are not well understood. For example, does the jitter response show an idiosyncratic signature? What is the relationship between stimuli properties and jitter properties? Is the jitter response similar across effectors with different inertial properties? To answer these questions, we measured participants' jitter frequencies in two tracking tasks in the arm and the finger. Thirty participants tracked the same set of eleven non-regular oscillating stimuli, vertically moving on a screen, once with forward-backward arm movements (holding a tablet stylus) and once with upward-downward index finger movements (with a motion tracker attached). Participants' jitter frequencies and tracking errors varied systematically as a function of stimuli frequency and amplitude. Additionally, there were clear individual differences in average jitter frequencies between participants, ranging from 0.7 to 1.15 Hz, similar to values reported previously. A comparison of individual jitter frequencies in the two tasks showed a strong correlation between participants' jitter frequencies in the finger and the arm, despite the very different inertial properties of the two effectors. This result suggests that the corrective jitter response stems from common neural processes.
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Awasthi, B., Sowman, P. F., Friedman, J., & Williams, M. A. (2013). Distinct spatial scale sensitivities for early categorisation of Faces and Places: Neuromagnetic and Behavioural Findings. Frontiers in Human Neuroscience, 7(91).
Abstract: Research exploring the role of spatial frequencies in rapid stimulus detection and categorisation report flexible reliance on specific spatial frequency bands. Here, through a set of behavioural and magnetoencephalography (MEG) experiments, we investigated the role of low spatial frequency (LSF)(25 cpf) information during the categorisation of faces and places. Reaction time measures revealed significantly faster categorisation of faces driven by LSF information, while rapid categorisation of places was facilitated by HSF information. The MEG study showed significantly earlier latency of the M170 component for LSF faces compared to HSF faces. Moreover, the M170 amplitude was larger for LSF faces than for LSF places, whereas the reverse pattern was evident for HSF faces and places. These results suggest that spatial frequency modulates the processing of category specific information for faces and places.
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Portnoy, S., Rosenberg, L., Alazraki, T., Elyakim, E., & Friedman, J. (2015). Differences in Muscle Activity Patterns and Graphical Product Quality in Children Copying and Tracing Activities on Horizontal or Vertical Surfaces. Journal of Electromyography and Kinesiology, 25(3), 540�547.
Abstract: The observation that a given task, e.g. producing a signature, looks similar when created by different motor commands and different muscles groups is known as motor equivalence. Relatively little data exists regarding the characteristics of motor equivalence in children. In this study, we compared the level of performance when performing a tracing task and copying figures in two common postures: while sitting at a desk and while standing in front of a wall, among preschool children. In addition, we compared muscle activity patterns in both postures. Specifically, we compared the movements of 35 five- to six-year old children, recording the same movements of copying figures and path tracing on an electronic tablet in both a horizontal orientation, while sitting, and a vertical orientation, while standing. Different muscle activation patterns were observed between the postures, however no significant difference in the performance level was found, providing evidence of motor equivalence at this young age. The study presents a straightforward method of assessing motor equivalence that can be extended to other stages of development as well as motor disorders.
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Raveh, E., Friedman, J., & Portnoy, S. (2018). Evaluation of the effects of adding vibrotactile feedback to myoelectric prosthesis users on performance and visual attention in a dual-task paradigm. Clin Rehabil, 99(11), 2263–2270.
Abstract: Objective: To evaluate the effects of adding vibrotactile feedback to myoelectric prosthesis users on the performance time and visual attention in a dual-task paradigm.
Design: A repeated-measures design with a counterbalanced order of two conditions.
Setting: Laboratory setting.
Subjects: Transradial amputees using a myoelectric prosthesis with normal or corrected eyesight (N=12, median age=65 ± 13 years). Exclusion criteria were orthopedic or neurologic problems.
Interventions: Subjects performed grasping tasks with their prosthesis, while controlling a virtual car on a road with their intact hand. The dual task was performed twice: with and without vibrotactile feedback.
Main measures: Performance time of each of the grasping tasks and gaze behavior, measured by the number of times the subjects shifted their gaze toward their hand, the relative time they applied their attention to the screen, and percentage of error in the secondary task.
Results: The mean performance time was significantly shorter (P=0.024) when using vibrotactile feedback (93.2 ± 9.6 seconds) compared with the performance time measured when vibrotactile feedback was not available (107.8 ± 20.3seconds). No significant differences were found between the two conditions in the number of times the gaze shifted from the screen to the hand, in the time the subjects applied their attention to the screen, and in the time the virtual car was off-road, as a percentage of the total game time
(51.4 ± 15.7 and 50.2 ± 19.5, respectively).
Conclusion: Adding vibrotactile feedback improved performance time during grasping in a dual-task paradigm. Prosthesis users may use vibrotactile feedback to perform better during daily tasks, when multiple cognitive demands are present.
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