Cognitive Biomedical Engineering
Elnaz Hamze; Zahra Bahmani Dehkordi; Mohammad Rostami
Volume 17, Issue 1 , May 2023, , Pages 31-40
Abstract
Working memory (WM) is an important cognitive function. Since WM capacity is limited, extensive research has been executed to improve it. Previous studies demonstrated that applying transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) enhances visual WM. ...
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Working memory (WM) is an important cognitive function. Since WM capacity is limited, extensive research has been executed to improve it. Previous studies demonstrated that applying transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) enhances visual WM. Capacity enhancement of WM has a significant effect on the pilot's efficiency. However, little is known about the auditory-verbal WM of Pilots. Therefore, the aim of this study is to evaluate the effects of tDCS over the left DLPFC on the WM capacity augmentation of pilots. The auditory-verbal WM stimuli comprise characters that are random numbers and alphabet letters. The stimulus is presented through the pilot's headset, and he has been persuaded to memorize the auditory stimulus and repeat the memorized characters. The auditory task is a set of 30 voices and is designed in 6 stages. The task starts from the easiest stage (4 characters) and continues with 2 increments of characters per stage to the most difficult stage (14 characters). The experiment was conducted under three conditions: baseline, sham, and anodal-tDCS. Before running the task, 2mA electrical stimulation with a duration of 30 seconds for the sham and 10 minutes for the anodal-tDCS conditions, was applied over the left DLPFC region of pilots. The performance measure is the number of correct remembered characters. Statistical hypotheses showed significant effects of anodal-tDCS in comparison to baseline condition as follows: %6.41 WM enhancement by considering all stages; and also improved performance around %12.20 in stage 4, %9.00 in stage 5, and %10.44 in stage 6 which are the most difficult stages. As a result, we found that 2mA anodal-tDCS over the left DLPFC can modulate WM capacity. The current study can be utilized to discover evidence of cognitive, behavioral, or neural mechanisms of WM and its application for human augmentation.
Medical Instrumentation
Zahra-Sadat Fatemi; Mohammad Mahdi Ahmadi
Volume 12, Issue 3 , November 2018, , Pages 221-234
Abstract
The use of smart medical implants to study the human brain and the interaction of neurons with each other has recently gained much attention. These implants contain microelectrode arrays in which the size of an electrode is in the order of the size of a neuron; therefore they allow recording signals ...
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The use of smart medical implants to study the human brain and the interaction of neurons with each other has recently gained much attention. These implants contain microelectrode arrays in which the size of an electrode is in the order of the size of a neuron; therefore they allow recording signals from single neuron or stimulating a single neuron with considerable precision. Design of such implants entails many challenges, one of which is the design of power and data recovery blocks. In this paper, we describe the design of a new power and data recovery unit for an implantable neural stimulating microsystem. The power recovery unit generates two supply voltages: a 1.8-V supply for the core circuits and a higher supply voltage for the stimulation front-end. An active rectifier is used to generate the 1.8-V supply. The active rectifier achives a 89% power conversion efficiency and 150mV voltage drop with a 3-V sinusoidal input voltage. In order to maximize the efficiency of the stimulation front-end, the supply voltage of that circuit should be adaptively adjusted according to the amplitude of the stimulation current. As a result, a phase-controlled active rectifier is utilized to generate the supply voltage for the neural stimulation front-end. The phase-controlled active rectifier can generate out voltages ranging from 1.8V to 2.5V. Using phase-controlled active rectifier can increase the power conversion efficiency up to 50%. In addition to power recovery, neuroelectrical stimulation microsystems should receive stimulation data from outside of the body. Hence, this paper also circuits required for clock and daterecovery. The data recovery block is able to demodulate the ASK-modulated signal with 3-V to 5-V amplitude and 5% to 25% modulation index.
Neuro-Muscular Engineering
Amir Masoud Ahmadi; Sepideh Farakhor Seghinsara; Mohamad Reza Daliri; Vahid Shalchyan
Volume 11, Issue 1 , May 2017, , Pages 83-100
Abstract
The brain stimulation and its widespread use is one of the most important subjects in studies of neurophysiology. In brain electrical stimulation methods, following the surgery and electrode implantation, electrodes send electrical impulses to the specific targets in the brain. The use of this stimulation ...
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The brain stimulation and its widespread use is one of the most important subjects in studies of neurophysiology. In brain electrical stimulation methods, following the surgery and electrode implantation, electrodes send electrical impulses to the specific targets in the brain. The use of this stimulation method is provided therapeutic benefits for treatment chronic pain, essential tremor, Parkinson’s disease, major depression, and neurological movement disorder syndrome (dystonia). One area in which advancements have been recently made is in controlling the movement and navigation of animals in a specific pathway. It is important to identify brain targets in order to stimulate appropriate brain regions for all the applications listed above. An animal navigation system based on brain electrical stimulation is used to develop new behavioral models for the aim of creating a platform for interacting with the animal nervous system in the spatial learning task. In the context of animal navigation the electrical stimulation has been used either as creating virtual sensation for movement guidance or virtual reward for movement motivation. In this paper, different approaches and techniques of brain electrical stimulation for this application has been reviewed.
Biological Computer Modeling / Biological Computer Simulation
Siamak Haghipour; Seyed Mohammad Reza Hashemi Golpayegani; Seyed Mohammad Firouzabadi; Sirous Momenzadeh
Volume 3, Issue 3 , June 2009, , Pages 227-241
Abstract
The procedure of pain formation embarks on primary sensory neurons and then ends in central nervous system which is the first stage in the dorsal horn of the spinal cord. Nowadays the great challenge of some researchers for pain control has been to elucidate the mechanisms that are able to switch the ...
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The procedure of pain formation embarks on primary sensory neurons and then ends in central nervous system which is the first stage in the dorsal horn of the spinal cord. Nowadays the great challenge of some researchers for pain control has been to elucidate the mechanisms that are able to switch the state of the dorsal horn of the spinal cord from an unwanted state to a favorite one. In order to achieve such an aim, a model of the function of the dorsal horn of the spinal cord is extracted in order to be able to control the created pains with changing the parameters of the aforementioned model. In this study a cybernetic model is presented with the aid of bifurcation methodologies and reconstructing the dynamics linked with the process of pain formation via clinical experiment that can express different states in the dorsal horn of the spinal cord as normal, suppressed, sensitized, the functionality of memory, the effect of other primary afferents and the effect of descending signals. Input signals in this model consist of thermal stimulation degree proportional to action potential firing rate from Ab afferents, inhibitory descending signals from midbrain and inhibitory or excitatory descending signal from thalamus and cortex and the output signal is the action potential firing rate from transmission cells in dorsal horn of the spinal cord proportional to pain level have been sensed. The significant and remarkable characteristic of this model is applying a cybernetical model based on a sequence of input-output data which can obviate the drawbacks of other models in which simplification and reduction of terms reduce the operation of components of a system. On the other hand, unlike previous models which have been modeled based on membrane (slow) potential, this model is based on the action potential firing rate from transmission cells of the dorsal horn of the spinal cord that has the adaptability with cellular recording as well as having a higher accuracy.
Hamed Sajedi; Seyed Ahmad Motamedi; Seyed Mohammad Firouzabadi
Volume -1, Issue 1 , June 2004, , Pages 3-14
Abstract
Auditory nerve fibers stimulating using electrical current with implanted electrodes are the basis of cochlear implant system. Therefore, expansion of current spread in volume conductor will change the electrical potential in a larger region. This expansion causes larger region stimulation and decreases ...
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Auditory nerve fibers stimulating using electrical current with implanted electrodes are the basis of cochlear implant system. Therefore, expansion of current spread in volume conductor will change the electrical potential in a larger region. This expansion causes larger region stimulation and decreases the accuracy and resolution of the stimulation in both the possibility of investigation of a particular region at Neural Response Telemetry (NRT) tests and also in hearing stimulation. Therefore, narrowing the width of stimulated region is the main goal in the selective stimulation. The conventional multi polar stimulation methods use lateral inhibitory electrode to form the spatial pattern of the electrical potential distribution for narrowing the stimulated region, but it needs to simultaneous stimulation of the electrodes, which is not available in implanted systems. In this paper, a new non-simultaneous multi-electrode stimulation method has been presented, which is based on applying the inhibitory pre-pulses by lateral electrodes. Inhibitory effect of the lateral electrodes pulses changes the initial conditions of the fibers and their thresholds. The results of simulations show that this method will solve the problem of simultaneous stimulation in conventional tri-polar stimulation methods and also is effective at controlling of stimulation area, comparing with tri-polar stimulation area, qualitatively and quantitatively.
