Neural Engineering / Neuroengineering / Brain Engineering
Ghazaleh Soleimani; Mehrdad Saviz; Farzad Towhidkhah; Hamed Ekhtiari
Volume 14, Issue 3 , October 2020, , Pages 251-266
Abstract
Transcranial direct current stimulation (tDCS) is the most-used non-invasive brain stimulation method. However, the main challenge in tDCS studies is its heterogeneity and large inter-individual variability in response. Brain anatomy, that varies from person to person, can change electric field distribution ...
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Transcranial direct current stimulation (tDCS) is the most-used non-invasive brain stimulation method. However, the main challenge in tDCS studies is its heterogeneity and large inter-individual variability in response. Brain anatomy, that varies from person to person, can change electric field distribution patterns in the brain and should be considered as a source of variation. Previous findings support that tDCS-induced EFs affect brain activity and ultimately change behavioral outcomes. Nonetheless, the exact relationship between EFs and brain activity alterations has not yet been investigated. In this randomized double-blinded sham-controlled crossover study, 14 subjects with methamphetamine use disorders were recruited and tDCS with 2 mA current intensity was applied over the dorsolateral prefrontal cortex. Each subject participated in two sessions for sham or real stimulation with at least a 1-week washout period. In each session, structural and functional MRI during a cue-induced craving task were collected immediately before and after tDCS. Individualized computational head models were simulated based on structural MR images and finite element methods. Group-level analysis of the models showed inter-individual variability across the subjects with maximum electric field intensity in frontal pole (0.3424±0.07). Furthermore, functional data, based on a drug minus neutral contrast, showed that real versus sham stimulation decreased brain activity in superior temporal gyrus and posterior cingulate cortex (P<0.001). However, we did not find a significant correlation between induced EFs and brain activity alterations. In sum, in this study, we suggested a pipeline for integrating electric fields with functional neuroimaging data to bring new insights into the tDCS mechanism of action and future studies are required to establish, or to refute, this conclusion.
Gait Analysis
Ghazaleh Soleimani; Mehran Emadi Andani; Hamid Reza Marateb; Fariba Bahrami
Volume 9, Issue 4 , February 2015, , Pages 361-374
Abstract
Walking is one of the most widely used movements affecting life quality. Therefore, the study of factors affecting human gait has always been an important issue. Walking speed, as a physical perturbation, affects the quality of human walking. The purpose of this study is to estimate the effects of walking ...
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Walking is one of the most widely used movements affecting life quality. Therefore, the study of factors affecting human gait has always been an important issue. Walking speed, as a physical perturbation, affects the quality of human walking. The purpose of this study is to estimate the effects of walking speed on the short-time gait parameters. Thirty-two healthy subjects(mean SD, age: 27.56 ± 20.4 years; body height: 158.19 ± 20.83 cm; body weight: 54.89 ± 20.59 kg;gender: 59% female)participated in this study.Kinetic, kinematic and electromyographic data were recorded at the following five walking speed categories: very slow, slow, medium, fast and very fast. The effect of speed on spatio-temporal parameters, muscle synergy space, walking smoothness, representation of joints displacement and the correlation between lower limb displacement and also correlation between muscles activation patterns were studied. Having being used physical perturbation, 46 predictors were extracted from one gait cycle information, some of which were proposed for the first time inthe literature for example size of muscle synergy, minimum angular jerk, lower limb contributions and skewness, kurtosis and curvature of joints movements . Using muscle synergies showed that increasing walking speed leads to increase the size of synergy space. It could be concluded that central nervous system tries to adopt more organaized strategy for recruiting muscles and remaining stable at fast speeds. Our results showed that, speed plays a crucial role in human gait characteristic. We can investigate our methods among more subjects and also patients with gait disorders. We can evaluate other indices like gait stability based on short-term data recording.
