Sharif Digital Repository

Electroencephalogram (EEG) is a noninvasive, low-cost brain recording tool with high temporal but poor spatial resolution. In contrast, functional magnetic resonance imaging (fMRI) is a rather expensive brain recording tool with high spatial and poor temporal resolution. In this study, we aim at recovering the brain activity (source localization and activity-intensity) with high spatial resolution using only EEG recordings. Each EEG electrode records a linear combination of the activities of various parts of the brain. As a result, a multi-electrode EEG recording represents the brain activities via a linear mixing matrix. Due to distance attenuation, this matrix is almost sparse. Using... 

Food choice is one of the most fundamental and most frequent value-based decisions for all animals including humans. However, the neural circuitry involved in food-based decisions is only recently being addressed. Given the relatively fast dynamics of decision formation, electroencephalography (EEG)-informed fMRI analysis is highly beneficial for localizing this circuitry in humans. Here, by using the EEG correlates of evidence accumulation in a simultaneously recorded EEG-fMRI dataset, we found a significant role for the right temporal-parietal operculum (PO) and medial insula including gustatory cortex (GC) in binary choice between food items. These activations were uncovered by using the... 

A wideband integrated delay chain chip with 5-bit main delay control, two error correction bits, maximum delay of 125-and 3.9-ps delay resolution, designed and fabricated in a 0.18-μ m CMOS technology is presented. This delay chain is a cascade of seven passive internal-switched delay blocks which the five main bits are based on novel delay structures. The proposed delay structures are similar to second-, fourth-, and sixth-order all-pass networks and are robust to mismatch effects of resistive parasitics of transistor switches. Measurement results of the fabricated delay chain show 15.2-23.3-dB insertion loss and less than 3.3-ps rms delay error over the intended frequency band from 8-18... 

A novel trombone topology has been introduced for achieving controllable true time delay. The prominent aspect of the proposed topology is the ability to provide discrete variable delay with minimum insertion loss variation with delay settings. Furthermore, the effects of source impedance, output load, and line-terminating loads' impedance mismatch on group delay variation are theoretically investigated for the proposed trombone topology. Moreover, based on this new topology, a prototype trombone delay circuit has been designed and fabricated in 0.18- mu ext{m} CMOS technology, operating over the frequency bandwidth of 8-18 GHz. This 3-bit delay integrated circuit provides a maximum delay... 

A high-precision delay chain circuit integrated in a 0.18- mu ext{m} CMOS technology working in the frequency bandwidth of 8-18 GHz has been designed and tested. The designed delay control integrated circuit with 5-bit delay control provides a maximum delay of 125 ps and has a delay resolution of 3.9 ps. Measured delay error of the fabricated chip is less than 9.3%, making it a considerably accurate delay control circuit. Low delay-error performance has resulted from incorporating a novel delay cell in this delay chain circuit. This newly proposed delay cell is a lumped-element coupled transmission line loaded with a second-order all-pass network (APN). The APN-loaded coupled line delay... 

A wideband integrated delay chain chip with 5-bit main delay control, two error correction bits, maximum delay of 125-and 3.9-ps delay resolution, designed and fabricated in a 0.18-μ m CMOS technology is presented. This delay chain is a cascade of seven passive internal-switched delay blocks which the five main bits are based on novel delay structures. The proposed delay structures are similar to second-, fourth-, and sixth-order all-pass networks and are robust to mismatch effects of resistive parasitics of transistor switches. Measurement results of the fabricated delay chain show 15.2-23.3-dB insertion loss and less than 3.3-ps rms delay error over the intended frequency band from 8-18... 

Stimulus presentation is believed to quench neural response variability as measured by fano-factor (FF). However, the relative contributions of within-trial spike irregularity and trial-to-trial rate variability to FF fluctuations have remained elusive. Here, we introduce a principled approach for accurate estimation of spiking irregularity and rate variability in time for doubly stochastic point processes. Consistent with previous evidence, analysis showed stimulus-induced reduction in rate variability across multiple cortical and subcortical areas. However, unlike what was previously thought, spiking irregularity, was not constant in time but could be enhanced due to factors such as... 

Memory and motor deficits are commonly identified in Parkinson's disease (PD). 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is transformed to MPP+ via monoamine oxidase B (MAOB), which causes oxidative stress and destroys dopaminergic (DA) neurons in substantia nigra pars compacta (SNc) and is widely used to create animal models of PD. However, to-date, a comprehensive analysis of the MPTP effects on various aspects of PD does not exist. Here, we provide a systematic review and meta-analysis on the MPTP effects on memory and motor functions by analyzing 51 studies on more than one thousand animals mainly including rats and mice. The results showed that in addition to motor functions... 

Simultaneous recording of activity across brain regions can contain additional information compared to regional recordings done in isolation. In particular, multivariate pattern analysis (MVPA) across voxels has been interpreted as evidence for distributed coding of cognitive or sensorimotor processes beyond what can be gleaned from a collection of univariate effects (UVE) using functional magnetic resonance imaging (fMRI). Here, we argue that regardless of patterns revealed, conventional MVPA is merely a decoding tool with increased sensitivity arising from considering a large number of ‘weak classifiers’ (i.e., single voxels) in higher dimensions. We propose instead that ‘real’ multivoxel... 

In this paper, the problem of sending n-bit of data from a client to a server using an asymmetric communication channel is discussed where the line bandwidth from server to client is much higher than that of client to server. The goal is to provide a protocol for this problem so that the average number of actual bits sent by client to server becomes as low as possible. Assuming that data is drawn from an arbitrary distribution D, the average number of bits sent by client to server cannot be less than H(D), where H(D) is the binary entropy of D. This problem was first considered by Adler and Maggs [1]. They assumed that the distribution of D is known only by the server and introduced a... 

Background: Accurate targeting of brain areas for stimulation and/or electrophysiological recording is key in many therapeutic applications and basic neuroscience research. Nevertheless, there are currently no end-to-end packages that accommodate all steps required for exact localization, visualization, and targeting regions of interest (ROIs) using standard atlases and for designing skull implants. New Method: We have implemented a new processing pipeline that addresses this issue in macaques and humans including various preprocessing, registration, warping procedures, and 3D reconstructions, and provide a noncommercial open-source graphical software which we refer to as the MATLAB-based... 

While Covid-19 is, first and foremost, a pernicious physical illness, its highly contagious nature has led to significant disruption in social life and psychological stress, occasionally resulting in dire mental health consequences that are still not fully understood. To address this issue, a prospective longitudinal design study was conducted by administering standard self-reporting questionnaires covering the NEO-five factor inventory (NEO-FFI), shyness, alexithymia, autism quotient, anxiety, depression, and sensory processing sensitivity (SPS). A total of 114 participants (of which 71.93% were females) with an average age of 30.29 (standard deviation = 11.04) completed the survey before... 

Recent evidence demonstrates that long-term object value association can enhance visual search efficiency, a phenomenon known as value pop-out. However, the neural mechanism underlying this effect is not fully understood. Given the known role of the ventrolateral prefrontal cortex (vlPFC) in visual search and value memory, we recorded its single-unit activity (n = 526) in two macaque monkeys while they engaged in the value-driven search. Monkeys had to determine whether a high-value target was present within a variable number of low-value objects. Differential neural firing, as well as gamma-band power, indicated the presence of a target within ∼150ms of display onset. Notably, this... 

In this study, the effect of surface modified silver nanoparticles on the corrosion protection of an epoxy coating on mild steel was studied. An organosilane (3-methoxy silyl propyl metacrylate) was used as a surface modifier to increase the dispersability of the inorganic nanoparticles in the organic epoxy coating matrix. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to characterize the surface modified nanoparticles. Differential scanning colorimetry (DSC) was employed to study the effects of modified and unmodified nano-silver on the curing heat and glass transition temperature of the epoxy coatings. Salt spray and electrochemical impedance... 

It is known that brain can create a sparse representation of the environment in both sensory and mnemonic forms (Olshausen & Field, 2004). Such sparse representation can be combined in downstream areas to create rich multisensory responses to support various cognitive and motor functions. Determining the components present in neuronal responses in a given region is key to deciphering its functional role and connection with upstream areas. One approach for parsing out various sources of information in a single neuron is by using linear blind source separation (BSS) techniques. However, applying linear techniques to neuronal spiking activity is likely to be suboptimal due to inherent and... 

A wideband integrated delay chain chip with 5-bit delay control, maximum delay of 120 ps and 3.9 ps delay resolution, designed and fabricated in 0.18 μ m CMOS technology is presented. Second-order all pass networks (APN) are used as delay structures in this delay circuit. In the design of the two MSB bits of the fabricated chip, a new design approach is used which allows higher group delay to be achieved with fewer number of passive second-order APN circuits. This would in turn reduce insertion loss of the designed delay control chain. Measurement results of the fabricated delay chain show 12.6–20.5 dB insertion loss and less than 3.3 ps RMS delay error over the intended frequency band from... 

To characterize the role of specimen disturbance and structure in the hydromechanical behavior of collapsible soils, two sets of wetting-induced collapse and suction-controlled triaxial tests were conducted on intact and reconstituted specimens of a loessial soil taken from a loess deposit in Gorgan, a city in the northeastern Golestan province of Iran. The testing approach used an advanced triaxial testing device that was specifically modified to control pressures applied to a soil specimen and to monitor and measure the amount of changes in volume and water content of the soil specimens during testing using highly sensitive digital sensors with an accuracy of 60.01 cm3. Results of the... 

Being able to track objects that surround us is key for planning actions in dynamic environments. However, rigorous cognitive models for tracking of one or more objects are currently lacking. In this study, we asked human subjects to judge the time to contact (TTC) a finish line for one or two objects that became invisible shortly after moving. We showed that the pattern of subject responses had an error variance best explained by an inverse Gaussian distribution and consistent with the output of a biased drift-diffusion model. Furthermore, we demonstrated that the pattern of errors made when tracking two objects showed a level of dependence that was consistent with subjects using a single... 

A neural probe made from a thin semiconductor material using an affordable microfabrication method is fabricated and characterized based on conventional measurements. The 4 microelectrodes with a surface area of 30 imes 100 mu mathrm{m}{2}, as well as the tracks and pads of the probe were constructed using a thin layer of gold (Au) material, with an insulating layer of SU-8 used to cover the corresponding tracks. To assess the performance of the fabricated probe, both Electrochemical Impedance Spectroscopy (EIS) and artificial stimulation methods were used to characterize its properties. The microelectrode dimensions were specifically chosen to provide low impedance characteristics, which... 

This effort attempts to study the change point problem in the area of non-linear profiles. A method based on Artificial Neural Networks (ANN) is proposed for estimating the real time of a single step change. The feature vector of the proposed Multi-Layer Perceptron (MLP) is based on Z and control chart statistics for nonlinear profiles. The merits of the proposed estimator are evaluated through simulation experiments. The results show that the estimator provides an accurate estimate of the single step change point in non-linear profiles in the selected case problem. © 2021, The Society for Reliability Engineering, Quality and Operations Management (SREQOM), India and The Division of...