Biological Systems Modeling
Mohsen Kamelian Rad; Mohammad Ali Ahmadi Pajouh; Mehrdad Saviz
Volume 15, Issue 2 , August 2021, , Pages 175-186
Abstract
Transcutaneous electrical stimulation of peripheral nerve fibers has always been an important field of research. Many studies indicate the possibility to block the conduction of nerve fibers by using high frequency alternating currents (HFAC). According to the fact that the stimulation of narrower fibers ...
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Transcutaneous electrical stimulation of peripheral nerve fibers has always been an important field of research. Many studies indicate the possibility to block the conduction of nerve fibers by using high frequency alternating currents (HFAC). According to the fact that the stimulation of narrower fibers is always accompanied by activation of thicker fibers, in this study, current regions for selective stimulation of different nerve fibers without activating other fibers have been obtained. This success is achieved through the nerve conduction block using HFAC (5-20 KHz). Stimulation current regions is a part of the intensity-frequency diagram which by choosing the excitation parameters in this area, only some target fibers are stimulated according to their diameters. The McIntyre nerve fiber model was used to perform these simulations; The sodium-potassium pump model has also been added to it and its effects have been investigated. A unipolar electrode is considered which acts as a point current source at different distances from the nerve fibers, and selective excitation spaces are obtained for the Aδ and Aβ fibers. The appropriate frequency range for excitation of different fibers is 5 kHz and above, while the desired current for selective excitation of Aδ and Aβ fibers is given by two polynomial equations of order 2 and 3, respectively, which are fitted to the middle of selective parameter space of each nerve fiber. Also, the excitation current varies from about 0.8 to 1.8 mA for Aδ fibers and from about 0.55 to 0.95 mA for Aβ fibers. In all of the simulations mentioned in this article, the sinusoidal waveform is used.
Medical Robotics / Bio-Robotics
Elaheh Kafashi; Mohammad Ali Ahmadi Pajouh; Firooz Bakhtiari Nejad
Volume 14, Issue 4 , February 2021, , Pages 277-290
Abstract
Due to the high number of patients with cerebrovascular disease and stroke, which results in paralysis of organs on one side of the body, including the hand, as well as limitations in traditional rehabilitation methods, it is necessary to build devices to help these people. In this study, initially, ...
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Due to the high number of patients with cerebrovascular disease and stroke, which results in paralysis of organs on one side of the body, including the hand, as well as limitations in traditional rehabilitation methods, it is necessary to build devices to help these people. In this study, initially, given the challenges involved in designing an exoskeleton, the initial design was a mechanism for using it as a continuous passive motion to rehabilitate the fingers. This mechanism is tendon-based and covers both the flexion and extension of the fingers. For this purpose, two active and passive actuators have been used in the exoskeleton, respectively, to flex and extend the fingers. The distinctive feature of this design is its lightness, low volume, adjustability for different hands, compatibility, and comfort for the patient. Also, the kinematics and dynamics relationships modeled on the Lagrange method. The exoskeleton movement simulated in interaction with the finger with MATLAB sim-mechanics software. Finally, using simulation and modeling results, the final design was performed by considering the force of 40 N along the tendon, the exoskeleton made for the index finger. Also, the results of analytical modeling and simulation compared; the error rate of modeling obtained. In the worst case, this value was 15% for the first and second finger joints and 20% for the third joint.
Computational Neuroscience
Maryam Sadeghi Talarposhti; Mohammad Ali Ahmadi-Pajouh; Frazad Towhidkhah
Volume 14, Issue 4 , February 2021, , Pages 333-344
Abstract
Human being is capable of performing more than one task simultaneously. This ability has been investigated in many researches. Performing more than one task at the same time has always been a challenging topic in psychology and human perception fields. The output and the effect of two tasks have been ...
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Human being is capable of performing more than one task simultaneously. This ability has been investigated in many researches. Performing more than one task at the same time has always been a challenging topic in psychology and human perception fields. The output and the effect of two tasks have been studied in previous researches for understanding the brain’s performance and also the disease origin and the symptoms. The influence of different difficulty levels has been explored via discrete-continuous motor-cognitive dual-task (DT). To this aim, a manual tracking task combined with discrete auditory stimuli to establish DT procedure. Twenty-five participants in this paradigm were asked to track the target on screen while reacting to the auditory task at the same time. Two levels of difficulty in manual tracking plus a single auditory task (ST) were considered for the experiment. The variability of output via different difficulties was investigated by analyzing factors of error rate and the response time (RT). For this analysis, a Drift Diffusion Model (DDM) method was used. In this 4-parameter model, the drift parameter is assumed to show the difficulty levels. The results show that by applying different drift rates (the average of 0.5, 0.3, and 0.2), the model is consistent with experimental output RT and the drift factor has the potential to be considered as the difficulty factor in the DT procedure.
