arXiv subjects

Reza Ebrahimpour

Publications and source records attributed to Reza Ebrahimpour.

12 recordsLinked to original sources

arXiv2025

Recency effect disappears when information is integrated from independent perceptual sources

Decision-making often involves integrating discrete pieces of information from distinct sources over time, yet the cognitive mechanisms underlying this integration remain unclear. In this study, we examined how individuals accumulate and integrate discrete sensory evidence. Participants performed a task involving random dot motion stimuli presented in single- and double-pulse trials. These stimuli varied in motion coherence, source consistency of pulses (either the same or orthogonal directions), and temporal gaps between pulses. We found that participants effectively integrated information regardless of source type or temporal gaps. As expected, when both pulses originated from the same source, performance showed a sequence-dependent effect-accuracy was influenced by the order of pulse presentation. However, this effect disappeared when the pulses came from orthogonal sources. Confidence judgments were similarly unaffected by temporal gaps or pulse sequence but were higher when information originated from orthogonal sources. These findings highlight the specific role of perceptual independency on information integration and consequently, on decision-making.

q-bio.NC↗

arXiv2025

Cueless EEG imagined speech for subject identification: dataset and benchmarks

Electroencephalogram (EEG) signals have emerged as a promising modality for biometric identification. While previous studies have explored the use of imagined speech with semantically meaningful words for subject identification, most have relied on additional visual or auditory cues. In this study, we introduce a cueless EEG-based imagined speech paradigm, where subjects imagine the pronunciation of semantically meaningful words without any external cues. This innovative approach addresses the limitations of prior methods by requiring subjects to select and imagine words from a predefined list naturally. The dataset comprises over 4,350 trials from 11 subjects across five sessions. We assess a variety of classification methods, including traditional machine learning techniques such as Support Vector Machines (SVM) and XGBoost, as well as time-series foundation models and deep learning architectures specifically designed for EEG classification, such as EEG Conformer and Shallow ConvNet. A session-based hold-out validation strategy was employed to ensure reliable evaluation and prevent data leakage. Our results demonstrate outstanding classification accuracy, reaching 97.93%. These findings highlight the potential of cueless EEG paradigms for secure and reliable subject identification in real-world applications, such as brain-computer interfaces (BCIs).

cs.LG↗

arXiv2024

Choice confidence bridges credit assignment to levels of decision hierarchy

Everyday decisions often involve many different levels. What connects these higher and lower level decisions hierarchy to one another determines how the cause(s) of failures are interpreted. It is hypothesized that decision confidence guides the assignment of blame to the correct level of hierarchy but this hypothesis has only been tested by manipulation of sensory evidence itself. We examined the consequences of modulating subjective confidence in hierarchical decision making via extra-sensory, social influence. Participants who made hierarchical, motion-plus-bandit decisions also received social information from a partner that advised the participant in the motion task. The strength of social advice -- independently from sensory signals -- modulated the likelihood of strategy change after negative feedback. Our findings therefore provide strong empirical evidence that subjective confidence per se acts as the bridge in assignment of credit and blame to various levels of decision hierarchy.

q-bio.NC↗

arXiv2024

Compensatory Mechanisms in Non-principal Multimedia Learning: The Interplay of Local and Global Information Processing

Educational multimedia has become increasingly important in modern learning environments because of its cost-effectiveness and ability to overcome the temporal and spatial limitations of traditional methods. However, the complex cognitive processes involved in multimedia learning pose challenges in understanding its neural mechanisms. This study employs network neuroscience to investigate how multimedia design principles influence the underlying neural mechanisms by examining interactions among various brain regions. Two distinct multimedia programs were constructed using identical auditory content but differing visual designs: one adhered to five guidelines for optimizing multimedia instruction, referred to as principal multimedia, while the other intentionally violated these guidelines, referred to as non-principal multimedia. Cortical functional brain networks were then extracted from EEG data to evaluate local and global information processing across the two conditions. Network measurements revealed that principal networks exhibited more efficient local information processing, whereas non-principal networks demonstrated enhanced global information processing and hub formation. Network modularity analysis also indicated two distinct modular organizations, with modules in non-principal networks displaying higher integration and lower segregation than those in principal networks, aligning with initial findings. These observations suggest that the brain may employ compensatory mechanisms to enhance learning and manage cognitive load despite less effective instructional designs.

q-bio.NC↗

arXiv2024

The Impact of Changes to Daylight Illumination level on Architectural experience in Offices Based on VR and EEG

This study investigates the influence of varying illumination levels on architectural experiences by employing a comprehensive approach that combines self-reported assessments and neurophysiological measurements. Thirty participants were exposed to nine distinct illumination conditions in a controlled virtual reality environment. Subjective assessments, collected through questionnaires in which participants were asked to rate how pleasant, interesting, exciting, calming, complex, bright and spacious they found the space. Objective measurements of brain activity were collected by electroencephalogram (EEG). Data analysis demonstrated that illumination levels significantly influenced cognitive engagement and different architectural experience indicators. This alignment between subjective assessment and EEG data underscores the relationship between illuminance and architectural experiences. The study bridges the gap between quantitative and qualitative assessments, providing a deeper understanding of the intricate connection between lighting conditions and human responses. These findings contribute to the enhancement of environmental design based on neuroscientific insights, emphasizing the critical role of well-considered daylighting design in positively influencing occupants' cognitive and emotional states within built environments.

cs.HC↗

arXiv2023

Age Effects on Decision-Making, Drift Diffusion Model

Training can improve human decision-making performance. After several training sessions, a person can quickly and accurately complete a task. However, decision-making is always a trade-off between accuracy and response time. Factors such as age and drug abuse can affect the decision-making process. This study examines how training can improve the performance of different age groups in completing a random dot motion (RDM) task. The participants are divided into two groups: old and young. They undergo a three-phase training and then repeat the same RDM task. The hierarchical drift-diffusion model analyzes the subjects' responses and determines how the model's parameters change after training for both age groups. The results show that after training, the participants were able to accumulate sensory information faster, and the model drift rate increased. However, their decision boundary decreased as they became more confident and had a lower decision-making threshold. Additionally, the old group had a higher boundary and lower drift rate in both pre and post-training, and there was less difference between the two group parameters after training.

q-bio.NC↗

arXiv2018

A temporal neural network model for object recognition using a biologically plausible decision making layer

Brain can recognize different objects as ones that it has experienced before. The recognition accuracy and its processing time depend on task properties such as viewing condition, level of noise and etc. Recognition accuracy can be well explained by different models. However, less attention has been paid to the processing time and the ones that do, are not biologically plausible. By extracting features temporally as well as utilizing an accumulation to bound decision making model, an object recognition model accounting for both recognition time and accuracy is proposed. To temporally extract informative features in support of possible classes of stimuli, a hierarchical spiking neural network, called spiking HMAX is modified. In the decision making part of the model the extracted information accumulates over time using accumulator units. The input category is determined as soon as any of the accumulators reaches a threshold, called decision bound. Results show that not only does the model follow human accuracy in a psychophysics task better than the classic spiking HMAX model, but also it predicts human response time in each choice. Results provide enough evidence that temporal representation of features are informative since they can improve the accuracy of a biological plausible decision maker over time. This is also in line with the well-known idea of speed accuracy trade-off in decision making studies.

q-bio.NC↗

arXiv2018

Sequence-dependent sensitivity explains the accuracy of decisions when cues are separated with a gap

Most decisions require information gathering from a stimulus presented with different gaps. Indeed, the brain process of this integration is rarely 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 in 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. The proposed model can also explain the stronger effect of the second pulse as shown by Kiani et al. 2013.

q-bio.NC↗

arXiv2017

Residual Information of Previous Decision Affects Evidence Accumulation in Current Decision

Bias in perceptual decisions comes to pass when the advance knowledge colludes with the current sensory evidence in support of the final choice. The literature on decision making suggests two main hypotheses to account for this kind of bias: internal bias signals are derived from (a) the residual of motor response-related signals, and (b) the sensory information residues of the decisions that we made in the past. Beside these hypotheses, a credible hypothesis proposed by this study to explain the cause of decision biasing, suggests that the decision-related neuron can make use of the residual information of the previous decision for the current decision. We demonstrate the validity of this assumption, first by performing behavioral experiments based on the two-alternative forced-choice (TAFC) discrimination of motion direction paradigms and then, we modified the pure drift-diffusion model (DDM) based on accumulation to the bound mechanism to account for the sequential effect. In both cases, the trace of the previous trial influences the current decision. Results indicate that the probability of being correct in a current decision increases if it is in line with the previously made decision. Also, the model that keeps the previous decision information provides a better fit to the behavioral data. Our findings suggest that the state of a decision variable which is represented in the activity of decision-related neurons after crossing the bound (in the previous decision) can accumulate with the decision variable for the current decision in consecutive trials.

q-bio.NC↗

arXiv2016

A specialized face-processing network consistent with the representational geometry of monkey face patches

Ample evidence suggests that face processing in human and non-human primates is performed differently compared with other objects. Converging reports, both physiologically and psychophysically, indicate that faces are processed in specialized neural networks in the brain -i.e. face patches in monkeys and the fusiform face area (FFA) in humans. We are all expert face-processing agents, and able to identify very subtle differences within the category of faces, despite substantial visual and featural similarities. Identification is performed rapidly and accurately after viewing a whole face, while significantly drops if some of the face configurations (e.g. inversion, misalignment) are manipulated or if partial views of faces are shown due to occlusion. This refers to a hotly-debated, yet highly-supported concept, known as holistic face processing. We built a hierarchical computational model of face-processing based on evidence from recent neuronal and behavioural studies on faces processing in primates. Representational geometries of the last three layers of the model have characteristics similar to those observed in monkey face patches (posterior, middle and anterior patches). Furthermore, several face-processing-related phenomena reported in the literature automatically emerge as properties of this model. The representations are evolved through several computational layers, using biologically plausible learning rules. The model satisfies face inversion effect, composite face effect, other race effect, view and identity selectivity, and canonical face views. To our knowledge, no models have so far been proposed with this performance and agreement with biological data.

q-bio.NC↗

arXiv2014

Capacity Theorems for the Cognitive Radio Channel with Confidential Messages

As a brain inspired wireless communication scheme, cognitive radio is a novel approach to promote the efficient use of the scarce radio spectrum by allowing some users called cognitive users to access the under-utilized spectrum licensed out to the primary users. Besides highly reliable communication and efficient utilization of the radio spectrum, the security of information transmission against eavesdropping is critical in the cognitive radios for many potential applications. In this paper, this problem is investigated from an information theoretic viewpoint. Capacity limits are explored for the Cognitive Radio Channel (CRC) with confidential messages. As an idealized information theoretic model for the cognitive radio, this channel includes two transmitters which send independent messages to their corresponding receivers such that one transmitter, i.e., the cognitive transmitter, has access non-causally to the message of the other transmitter, i.e., the primary transmitter. The message designated to each receiver is required to be kept confidential with respect to the other receiver. The secrecy level for each message is evaluated using the equivocation rate. Novel inner and outer bounds for the capacity-equivocation region are established. It is shown that these bounds coincide for some special cases. Specifically, the capacity-equivocation region is derived for a class of less-noisy CRCs and also a class of semi-deterministic CRCs. For the case where only the message of the cognitive transmitter is required to be kept confidential, the capacity-equivocation region is also established for the Gaussian CRC with weak interference.

cs.IT↗

arXiv2013

ECOC-Based Training of Neural Networks for Face Recognition

Error Correcting Output Codes, ECOC, is an output representation method capable of discovering some of the errors produced in classification tasks. This paper describes the application of ECOC to the training of feed forward neural networks, FFNN, for improving the overall accuracy of classification systems. Indeed, to improve the generalization of FFNN classifiers, this paper proposes an ECOC-Based training method for Neural Networks that use ECOC as the output representation, and adopts the traditional Back-Propagation algorithm, BP, to adjust weights of the network. Experimental results for face recognition problem on Yale database demonstrate the effectiveness of our method. With a rejection scheme defined by a simple robustness rate, high reliability is achieved in this application.

cs.CV↗