Papers by Reza Ebrahimpour
Guest Reviewers, Journal of Classification Volume 29, 2012
Journal of Classification, 2012
In addition to the members of the Editorial Board, the individuals listed below refereed manuscri... more In addition to the members of the Editorial Board, the individuals listed below refereed manuscripts that were submitted to the journal. Their assistance is gratefully acknowledged. ... Kohei Adachi Mohammed Al-Rawwash Amjad Al-Nasser Andres Alonso Tomas Aluja-Banet Pietro Amenta Carolyn J. Anderson Elizabeth Ayers Avner Bar-Hen Eric Beh Jos ten Berge Wicher Bergsma Christophe Biernacki Nicole Blackman Andrew Bradley Eugenio Brentari Paula Brito François Brucker Miroslav Burša Martine Cadot Gilles Celeux Andrea Cerioli Eva Ceulemans ...
Explaining Integration of Evidence Separated by a Temporal Gap with Fronto-Centroparietal Circuit Models
Social Science Research Network, 2022
Scientific Reports
Parkinson’s disease (PD) is associated with abnormal $$\beta$$ β band oscillations (13–30 Hz) in ... more Parkinson’s disease (PD) is associated with abnormal $$\beta$$ β band oscillations (13–30 Hz) in the cortico-basal ganglia circuits. Abnormally increased striato-pallidal inhibition and strengthening the synaptic coupling between subthalamic nucleus (STN) and globus pallidus externa (GPe), due to the loss of dopamine, are considered as the potential sources of $$\beta$$ β oscillations in the basal ganglia. Deep brain stimulation (DBS) of the basal ganglia subregions is known as a way to reduce the pathological $$\beta$$ β oscillations and motor deficits related to PD. Despite the success of the DBS, its underlying mechanism is poorly understood and, there is controversy about the inhibitory or excitatory role of the DBS in the literature. Here, we utilized a computational network model of basal ganglia which consists of STN, GPe, globus pallidus interna, and thalamic neuronal population. This model can reproduce healthy and pathological $$\beta$$ β oscillations similar to what has b...
The Neuroscience Journal of Shefaye Khatam
The basic human decision involves several s tages of consecutive decisions. In the presence of mu... more The basic human decision involves several s tages of consecutive decisions. In the presence of multi-s tage decisions, to avoid interruption in the sequence of decisions, there is no possibility to reques t a confidence report on the middle s tages. This inevitably makes to es timate the confidence of the decision. The challenges involved in applying behavioral data to determine confidence, make it more important to use other types of data. Since eye data is associated with the decision process, this s tudy examined the dynamics of involuntary information, in the context of multi-s tage decisions. The pupil size was applied as a valuable source to es timate the decision confidence. Material and Methods: A two-s tage psychophysical experiment was designed. In this experiment, participants were ins tructed to decide about the direction of moving dots in two successive s timuli (right or left for the firs t s tage and up or down for the second s tage). Participants were received correct feedback in a trial when they reported the correct direction of both s timuli. During the experiment, the eye movement data of the participants were recorded by an eye-tracking device. Results: The latency of the pupil diameter signal positive peak and pupil diameter at the time of response were meaningfully associated with decision confidence. Furthermore, the results demons trated that pupil size was altered in the current decision based on the confidence of the previous decision. Conclusion: This research es tablishes that in the multis tage decision making, the confidence of a decision is represented in involuntary information that can reflect the individual's s trategy in complex situations. In addition, the confidence of the previous decision can significantly change voluntary and involuntary behaviors in the same manner.
Parkinson’s disease (PD) is associated with abnormal b band oscillations (13-30 Hz) in the cortic... more Parkinson’s disease (PD) is associated with abnormal b band oscillations (13-30 Hz) in the cortico-basal ganglia circuits.Abnormally increased striato-pallidal inhibition and strengthening the synaptic coupling between subthalamic nucleus (STN)and globus pallidus externa (GPe), due to the loss of dopamine, are accounted as the potential sources of b oscillations in thebasal ganglia. Deep brain stimulation (DBS) of the basal ganglia subregions is known as a way to reduce the pathological boscillations and motor deficits related to PD. Despite the success of the DBS, its underlying mechanism is poorly understoodand, there is controversy about the inhibitory or excitatory role of the DBS in the literature. Here, we utilized a computationalnetwork model of basal ganglia which consists STN, GPe, globus pallidus interna (GPi), and thalamus neuronal population.This model can capture healthy and pathological b oscillations as what has been observed in experimental studies. Using thismodel, ...
The Neuroscience Journal of Shefaye Khatam, 2021
Introduction: We encounter different information or stimuli. However, the combination of these st... more Introduction: We encounter different information or stimuli. However, the combination of these stimuli and the quality of their presentation can influence our perception and decision. Despite the importance of these combined stimuli to our judgments and decisions, it is not yet clear how the characteristics of these stimuli affect the decision-making processes. For example, it is not clear whether the time interval between the information we receive can affect the accuracy and speed of decision-making. This study aimed to investigate the effect of the time interval between two different visual stimuli on perceptual decisionmaking. Materials and Methods: According to psychophysical experiments, it was possible to measure the response to perceptual stimuli and compare perceptual choices. In a Random Dot Motion (RDM), the task was displayed to the participants as the primary visual stimulus and a graphic cue as the second visual stimulus, at different intervals, and then the participant's decision accuracy and reaction time to each of these two stimuli were recorded and analyzed. Results: We found that in RDM (primary stimulus), the accuracy of participants' decisions are not affected by the time interval between the presentation of two stimuli. Instead, the accuracy of the response to the Cue (second visual stimulus) decreases in long time intervals between two stimuli. Interestingly, if two stimuli are presented simultaneously, the decision about each of these stimuli is reasonably accurate; yet, the speed of the decision-making process is slower than when a person encounters two stimuli separated by a time interval. Conclusion: The human visual system can distinguish visual stimuli that are presented with a short time interval in between; however, in exchange for correctly identifying these stimuli, the speed of decision-making may be slowed down.n
1. Cognitive Science Modeling, Shahid Beheshti University, Tehran, Iran 2. Post-Doctoral Research... more 1. Cognitive Science Modeling, Shahid Beheshti University, Tehran, Iran 2. Post-Doctoral Researcher, Institute for Research in Fundamental Sciences, School of Cognitive Sciences, Tehran, Iran 3. Associate Professor, Psychology Department, Faculty of Psychology, University of Tehran, Tehran, Iran & Institute for Cognitive Science Studies, Pardis, Iran 4. Professor, Artificial Intelligence Department, Faculty of Computer Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
Classifier fusion may generate more accurate classification than each of the basic classifiers. F... more Classifier fusion may generate more accurate classification than each of the basic classifiers. Fusion is often based on fixed combination rules like the product, average etc. This paper presents decision templates as classifier fusion method for the recognition of the handwritten English and Farsi numerals (1-9). The process involves extracting a feature vector on well-known image databases. The extracted feature vector is fed to multiple classifier fusion. A set of experiments were conducted to compare decision templates (DTs) with some combination rules. Results from decision templates conclude 97.99% and 97.28% for Farsi and English handwritten digits.
This paper illustrates the use of a combined neural network model for classification of electroca... more This paper illustrates the use of a combined neural network model for classification of electrocardiogram (ECG) beats. We present a trainable neural network ensemble approach to develop customized electrocardiogram beat classifier in an effort to further improve the performance of ECG processing and to offer individualized health care. We process a three stage technique for detection of premature ventricular contraction (PVC) from normal beats and other heart diseases. This method includes a denoising, a feature extraction and a classification. At first we investigate the application of stationary wavelet transform (SWT) for noise reduction of the electrocardiogram (ECG) signals. Then feature extraction module extracts 10 ECG morphological features and one timing interval feature. Then a number of multilayer perceptrons (MLPs) neural networks with different topologies are designed. The performance of the different combination methods as well as the efficiency of the whole system is ...
ABSTRACTParkinson’s disease (PD) is associated with abnormal β band oscillations (13-30 Hz) in th... more ABSTRACTParkinson’s disease (PD) is associated with abnormal β band oscillations (13-30 Hz) in the cortico-basal ganglia circuits. Abnormally increased striato-pallidal inhibition and strengthening the synaptic coupling between subthalamic nucleus (STN) and globus pallidus externa (GPe), due to the loss of dopamine, are considered as the potential sources of β oscillations in the basal ganglia. Deep brain stimulation (DBS) of the basal ganglia subregions is known as a way to reduce the pathological β oscillations and motor deficits related to PD. Despite the success of the DBS, its underlying mechanism is poorly understood and, there is controversy about the inhibitory or excitatory role of the DBS in the literature. Here, we utilized a computational network model of basal ganglia which consists of STN, GPe, globus pallidus interna (GPi), and thalamic neuronal population. This model can reproduce healthy and pathological β oscillations similar to what has been observed in experiment...
In this paper, a method for determination of refractive index in membrane of fuel cell on the bas... more In this paper, a method for determination of refractive index in membrane of fuel cell on the basis of three-longitudinal-mode laser heterodyne interferometer is presented. The optical path difference between the target and reference paths is fixed and phase shift is then calculated in terms of refractive index shift. The measurement accuracy of this system is limited by nonlinearity error. In this study, nonlinearity error is modeled by multi-layer perceptrons (MLPs) and stacked generalization method (Stacking), using two learning methods; back propagation (BP) and genetic algorithm. Training neural networks with genetic algorithm improves modeling of nonlinearity error in this system. In the proposed technique, a real code version of genetic algorithm is used. Parameters and genetic operators are set and designed accurately. The results indicate that the nonlinearity error can be effectively modeled by training the stacking with the genetic algorithm which has minimum mean square ...
Received: 28 April 2020 Reviewed: 19 June 2020 Revised: 31 August 2020 Accepted: 13 September 2020
When making decisions in real-life, we may receive discrete evidence during a time period. Althou... more When making decisions in real-life, we may receive discrete evidence during a time period. Although participants can integrate information from separate cues to improve their accuracy, it is still debatable how confidence changes after receiving discrete information. Nevertheless, based on the strong positive relationship between accuracy and confidence, we predicted that similar to what is observed in accuracy, confidence would improve following the integration of separate pieces of information. We used a Random-dot-motion discrimination task in which one or two brief stimuli (i.e., pulse[s]) were presented, and participants had to indicate the predominant direction of dot motions by saccadic eye movement. Two pulses intervals (up to 1s) were randomly selected, where color-coded targets facilitated indicating confidence simultaneously. Using behavioral data, computational models, pupillometry, and EEG methodology, our data revealed that compared to single-pulse trials, in double-pu...
A Novel Iterative Rigid Image Registration Algorithm Based on the Newton Method
International Journal of Image and Graphics, 2021
In recent years, Image Registration has attracted lots of attention due to its capabilities and n... more In recent years, Image Registration has attracted lots of attention due to its capabilities and numerous applications. Various methods have been exploited to map two images with the same concept but different conditions. Considering the finding of the mentioned map as an optimization problem, mathematical-based optimization methods have been extensively employed due to their real-time performances. In this paper, we employed the Newton method to optimize two defined cost functions. These cost functions are Sum of Square Difference and Cross-Correlation. These presented algorithms have fast convergence and accurate features. Also, we propose an innovative treatment in order to attend to one of the free parameter-rotations or scale as a sole variable and the other one as the constant value. The assignment is replaced through the iterations for both parameters. The intuition is to turn a two-variable optimization problem into a single variable one in every step. Our simulation on bench...
Modification and hardware implementation of cortex-like object recognition model
IET Image Processing, 2020
The Neuroscience Journal of Shefaye Khatam, 2019
Introduction: Others' decision could cons tantly affect our decisions. There are numerous s tudie... more Introduction: Others' decision could cons tantly affect our decisions. There are numerous s tudies which revealed this effect properly. The social influence could affect mos t of the decision parameters, especially the confidence. Recently, an interes ting s tudy showed that participants tend to match their confidence to each other while they preserve their decision accuracy in a group decision making task. Since the decision accuracy is not able to explain this effect, the main ques tion is which decision parameter is changing in a way which could be resulted in changing in the confidence and ultimately the confidence matching. Materials and Methods: In order to answer this ques tion, ten subjects attended into a Psycho-Physic s tudy with two separate sessions; Isolated and Social. In both situations, the participants were required to determine the direction of the presented motion dots and report their decision and confidence simultaneously. In the social situation, subjects were paired with four computergenerated partners, which had been created based on the data from the isolated session. The joint decisions were determined by the decision of either partner which had higher confidence. In this session, confidence and decision of the partner were represented to the participant. Results: The results indicated the subjects not only try to match their confidence to their partners, but also reported higher confidence in comparison with the isolated situation. We observed although the confidence matching did not affect the decision accuracy, however, the reaction time varied significantly in both sessions. Conclusion: This s tudy reveals the role of reaction time in changing the confidence and consequently the confidence matching. This s tudy once again emphasis on the reverse correlation of the reaction time and confidence even in a group decision making task.
Handwritten Farsi Word Recognition Using NN-Based Fusion of HMM Classifiers with Different Types of Features
International Journal of Image and Graphics, 2019
In this paper, an off-line method, based on hidden Markov model, HMM, is used for holistic recogn... more In this paper, an off-line method, based on hidden Markov model, HMM, is used for holistic recognition of handwritten words of a limited vocabulary. Three feature sets based on image gradient, black–white transition and contour chain code are used. For each feature set an HMM is trained for each word. In the recognition step, the outputs of these classifiers are combined through a multilayer perceptron, MLP. High number of connections in this network causes a computational complexity in the training. To avoid this problem, a new method is proposed. In the experiments on 16000 images of 200 names of Iranian cities, from “Iranshahr 3” dataset, the results of the proposed method are presented and compared with some similar methods. An error analysis on these results is also provided.
Attention, Perception, & Psychophysics, 2019
Most decisions require information gathering from a stimulus presented with different gaps. Howev... more Most decisions require information gathering from a stimulus presented with different gaps. However, the neural mechanism underlying this integration is ambiguous. Recently, it has been claimed that humans can optimally integrate the information of two discrete pulses independent of the temporal gap between them. Interestingly, subjects' performance on such a task, with two discrete pulses, is superior to what a perfect accumulator can predict. Although numerous neuronal and descriptive models have been proposed to explain the mechanism of perceptual decision-making, none can explain human behavior on this two-pulse task. In order to investigate the mechanism of decision-making on the noted tasks, a set of modified drift-diffusion models based on different hypotheses were used. Model comparisons clarified that, in a sequence of information arriving at different times, the accumulated information of earlier evidence affects the process of information accumulation of later evidence. It was shown that the rate of information extraction depends on whether the pulse is the first or the second one. Moreover, our findings suggest that a drift diffusion model with a dynamic drift rate can also explain the stronger effect of the second pulse on decisions as shown by Kiani et al.
The Neuroscience Journal of Shefaye Khatam, 2019
The basal ganglia are subcortical s tructures of the brain which are involved in the motor sys te... more The basal ganglia are subcortical s tructures of the brain which are involved in the motor sys tem. One of the common disorders related to malfunctioning of the basal ganglia is Parkinson's disease (PD). PD is accompanied by s trong and permanent beta band oscillations in the basal ganglia. Deep brain s timulation (DBS) of the subthalamic nucleus (STN) in the basal ganglia is known as an approach to reduce pathological beta oscillations in PD and to improve PD-related motor symptoms. Despite the success of this approach, its underlying mechanisms are s till unclear. Materials and Methods: In this s tudy, we proposed a computational network model for the cortico-basal ganglia loop based on the model sugges ted by Terman and colleagues earlier. We modified the network model in the manner that it can generate pathological beta oscillations in the PD s tate. Then, by applying different DBS scenarios (such as regular and irregular high frequency excitation of STN), we inves tigated which scenario is able to reduce the pathological beta power more efficiently. Results: Our results show that the network model can generate pathological beta band oscillations similar to what has experimentally been observed in the PD s tate. Our simulation results indicate that the regular DBS outperforms the irregular DBS, in terms of reducing the PD-related beta oscillations and improving the motor symptoms. Conclusion: Using our simulation results, we conclude that applying regular high frequency DBS on the STN neurons in the basal ganglia can ameliorate PD-related motor deficits better than irregular DBS pulses. This simulation result is experimentally tes table.
The Neuroscience Journal of Shefaye Khatam, 2016
Most decisions are based on the accumulation of discrete pieces of evidence. This evidence has us... more Most decisions are based on the accumulation of discrete pieces of evidence. This evidence has usually been separated with the various intervals. Indeed, how the brain gathers and combines distinct pieces of information received at different times is need to be clarified. In order to investigate the kinship between brain function and human behavior, the behavioral experimental studies could be designed. Previous studies demonstrated that subjects gather and effectively combine discrete evidence to improve their accuracy. In addition, it has been shown that the latest information has a larger influence on decisions. However, it remains unclear that why this larger influence of the later pulses occurs and what can affect this influence. Materials and Methods: Dealing with these questions a perceptual decision-making task has been implemented by the psychophysics' toolbox in MATLAB. Subjects, during the task, were instructed to report the direction of motion in a noisy random dot stimulus with certain keys. Stimuli were presented in continuous (one pulse) or discrete (two continuousness pulses separated with different intervals) form. Each of these two forms of stimuli was presented randomly during each session. Each session has been included 300 trials. Each subject has done 3600 trials. Data have been analyzed by regression models. Results: We observed that in double-pulse trials, the strength of the second pulse was more crucial in the accuracy of responses compared to the first pulse. In addition, this accuracy was dependent on the differences between the strength of the first and the last pulses. Conclusion: These findings suggest that a key factor which affects the importance of pulses is the strength of the previous pulse. As the difference between the motion strength increases, the effect of the second pulse on choice accuracy enhanced.
Uploads
Papers by Reza Ebrahimpour