Psycho-physiological assessment of a prosthetic hand sensory feedback system based on an auditory display: a preliminary study.

BACKGROUND: Prosthetic hand users have to rely extensively on visual feedback, which seems to lead to a high conscious burden for the users, in order to manipulate their prosthetic devices. Indirect methods (electro-cutaneous, vibrotactile, auditory cues) have been used to convey information from the artificial limb to the amputee, but the usability and advantages of these feedback methods were explored mainly by looking at the performance results, not taking into account measurements of the user's mental effort, attention, and emotions. The main objective of this study was to explore the feasibility of using psycho-physiological measurements to assess cognitive effort when manipulating a robot hand with and without the usage of a sensory substitution system based on auditory feedback, and how these psycho-physiological recordings relate to temporal and grasping performance in a static setting. METHODS: 10 male subjects (26+/-years old), participated in this study and were asked to come for 2 consecutive days. On the first day the experiment objective, tasks, and experiment setting was explained. Then, they completed a 30 minutes guided training. On the second day each subject was tested in 3 different modalities: Auditory Feedback only control (AF), Visual Feedback only control (VF), and Audiovisual Feedback control (AVF). For each modality they were asked to perform 10 trials. At the end of each test, the subject had to answer the NASA TLX questionnaire. Also, during the test the subject's EEG, ECG, electro-dermal activity (EDA), and respiration rate were measured. RESULTS: The results show that a higher mental effort is needed when the subjects rely only on their vision, and that this effort seems to be reduced when auditory feedback is added to the human-machine interaction (multimodal feedback). Furthermore, better temporal performance and better grasping performance was obtained in the audiovisual modality. CONCLUSIONS: The performance improvements when using auditory cues, along with vision (multimodal feedback), can be attributed to a reduced attentional demand during the task, which can be attributed to a visual "pop-out" or enhance effect. Also, the NASA TLX, the EEG's Alpha and Beta band, and the Heart Rate could be used to further evaluate sensory feedback systems in prosthetic applications.

Using piezoelectric films for classification of upper arm motions: a preliminary report.

Recently, it has been reported that finger motions could be recognized from the forearm signal detected by accelerometers. However, accelerometers are sensitive to vibration or unintended motions, which could cause large noise when classifying different hand motions. This is why our research group wanted to explore the usability of other kinds of sensors for upper arm motions classification. Therefore, the objective of this study was to examine the usefulness of a piezoelectric film for hand motion classification and its robustness to unintended motions. Experiments were conducted to record signals from the piezoelectric films for different hand motions, while the subject was asked to move the ipsilateral shoulder, the contralateral hand, or the legs. The results showed that the desired hand motion could be distinguished using a piezoelectric film despite of unintended motions.

Preliminary results of online classification of upper limb motions from around-shoulder muscle activities.

Recently, detecting upper-limb motion intention for prosthetic control purpose attracted growing research attention. In most of the studies, recordings of forearm muscle activities were used as the signal sources, from which the intention of wrist and hand motions were detected using pattern recognition technology. However, most daily-life upper limb activities need coordination of the shoulder-arm-hand complex. The disadvantage of relying only on the local information to recognize a whole body coordinated motion is that misrecognition could easily happen, so that steady and reliable continuous motions could not be realized. Moreover, using forearm muscle activities would limit the use of the system for higher level amputation patients. Therefore, in this study we aimed to explore the feasibility of using an online classification algorithm to test the intention detection in real time. Experiments were conducted to record around-shoulder muscle activity using EMG and acceleration sensors. Then, a neural network was trained using these data, and finally tested online in a set of tests. Results showed that, from 5 channels of Electromyogram (EMG) and 4 channels of accelerometers, it is possible to discriminate 3 different grips and 5 reaching direction of arm.

A study on the forearm muscular reflexes during grasping for prosthetic applications.

Recently, there has been an increasing interest in upper-limb prosthetic hand control, but most of these studies focus on the detection of exact motion intentions. Therefore, the responses to unexpected disturbance are not taken into consideration. On the other hand, unimpaired people respond to external disturbances by reflexive responses, hence, it is important to explore how this kind of reactive responses could be applied into prosthetic hand applications, and whether it will improve the human-machine interaction in a dynamical way. Our objective for the present study was to examine the responses of the human reflexes on different conditions in order to apply them to our prosthetic hand. Electromyograph (EMG) signals were recorded from the forearm muscles of unimpaired people during grasping of a cylinder. Results showed that the reflexes have different tendencies depending on the direction on which the disturbance is applied.