Browsing by Subject "ERP"

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Open Access
Audiovisual interactions in time and spatial grouping principles of vision
(2016-10) Öğülmüş, Cansu
Multisensory integration is often studied with intermodal con ict where either visual input dominates and alters the percept of simultaneous auditory input or the other way around. For instance, when put in con ict, visual stimuli can drive the perception of where a sound originates (spatial ventriloquism) [1, 2] whereas auditory stimuli can drive the perception of when visual events occur (temporal ventriloquism) [3, 4, 5] .These interactions make adaptive sense given the auditory system´s superior temporal resolution and the visual system´s superior spatial resolution [6]. Moreover, it was found that temporal ventriloquism can change the perceived speed of visual motion [7]. By taking advantage of this in uence of auditory timing on perceived speed, we investigated how audiovisual interactions in time (i.e., temporal ventriloquism) are modulated by the spatial grouping principles of vision. In our experiments, we manipulated spatial proximity, common fate and uniform connectedness between moving ashes. Observers compared the speed of motion between different auditory timing conditions. Our results revealed that auditory in uences on perceived speed were significantly modulated by only uniform connectedness. More specifically, we found that auditory effects on vision was significantly less when a horizontal gray connecting bar grouped multiple sequential moving ashes. When horizontally placed moving ashes were grouped with a vertical connecting bar, the degree of auditory in uences in time was significantly stronger compared to not grouped (control) and horizontal connecting bar conditions. The effect of auditory clicks on single apparent motion grouped with horizontal connecting bar was smaller relative to the not-grouped condition. In addition, our analysis on EEG activities revealed consistent trends in agreement with the behavioral results. Audiovisual interaction patterns were observed both earlier (around P1) and later (around N1 and P2). Less auditory capture over the horizontal connecting bar condition relative to the vertical connecting bar condition was observed around 50-100 ms (P1) on the frontal and temporal channels and around 200-300 ms (N1) on the frontal, central, temporal and occipital-parietal channels. The larger effect of sound over the single apparent motion without connecting bar condition was observed around 50-100 ms and 200-300 ms on the central channels and 200-300 ms on the occipital-parietal channels. The difference between the individual effects of inner and outer sound conditions was found to be less for the horizontal connecting bar condition relative to the vertical connecting bar condition over the frontal, temporal, central and occipital-parietal channels while less individual effects of the inner and outer sound conditions on the single apparent motion with horizontal connecting bar condition relative to the without connecting bar condition was only observed over the central channels and late time intervals of the occipital-parietal and temporal channels. Overall the individual effects of both sound conditions were consistently similar on the horizontal connecting bar condition (compared to the vertical connecting bar condition) for all ROIs and on the single apparent motion with horizontal connecting bar condition (compared to the no-connecting bar condition) over the central channels. In general, our findings here suggest that temporal ventriloquism effects exist in different spatial grouping conditions of vision, but they can be also modulated by certain intra-modal grouping principles such as uniform connectedness.
Open Access
A new time-frequency analysis technique for neuroelectric signals
(2002) Tüfekçi, D. İlhan
In the presence of external stimuli, the functioning brain emits neuroelectrical signals which can be recorded as the Event Related Potential (ERP) signals. To understand the brain cognitive functions, ERP signals have been the subject matter of many applications in the field of cognitive psychophysiology. Due to the non–stationary nature of the ERP signals, commonly used time or frequency analysis techniques fail to capture the time–frequency domain localized nature of the ERP signal components. In this study, the newly developed Time–Frequency Component Analyzer (TFCA) approach is adapted to the ERP signal analysis. The results obtained on the actual ERP signals show that the TFCA does not have a precedent in resolution and extraction of uncontaminated individual ERP signal components. Furthermore, unlike the existing ERP analysis techniques, the TFCA based analysis technique can reliably measures the subject dependent variations in the ERP signals, which iiiopens up new possibilities in the clinical studies. Thus, TFCA serves as an ideal tool for studying the intricate machinery of the human brain.
Open Access
Parasitic effects of the metallic towers on the characteristics of the broadcast antennas
(John Wiley and Sons, 2018) Ali, A.; Colantonio, P.; Altintas, A.
In this article, we use a tool NEC (Numerical Electromagnetic Code) to model antenna on top of a tower structure. Simulation results for the parasitic effect of the tower on characteristics of broadcast DVB-T (Digital Video Broadcasting Terrestrial) antenna such as input impedance, return loss, gain, front-to-back ratio and radiation patterns are reported. In addition, the effect of a nearby tower on antenna characteristics is studied. A 3D tower and broadband antenna in the UHF (470-862) MHz band are constructed. The antenna works for both digital and analog TV with return loss (RL) ≥ 10 dB, fractional bandwidth of 87% and gain of 12.3 dBi at center frequency. The effective radiated power is calculated by mounting the antenna at each face of the tower to give a satisfactory coverage to a region around the antenna.
Open Access
Predictive processing during novel word learning: ERP measures of vowel harmony
(2023-06) Müftüoğlu, Berrak
This project investigated the effect of Turkish vowel harmony (TVH) on the acquisition of multi-syllabic words via cross-situational word learning (CSWL). CSWL is an implicit learning paradigm requiring learners to statistically track word-referent pairs across ambiguous conditions. Although there are many studies have examined certain lexical conditions that span word boundaries, within-lexical unit characteristics, such as TVH, have not been examined. We conducted 2 experiments; Experiment 1 is an internet-based experiment with Native Turkish speakers and speakers of other languages, and Experiment 2 is an EEG experiment focusing on N400 and LPC ERPs with Native Turkish speakers. In experiment 1, participants received training and recognition test phases. During training, participants were presented with novel pseudowords, both harmonious and disharmonious for TVH, with multiple referent pictures. In the recognition test, participants heard a pseudoword and were asked to select the correct referent for it. The results of the first experiment did not show a significant difference. In experiment 2, learning was additionally measured by a semantic judgment task (SJT). In the SJT, participants were presented with either a learned pseudoword or a real Turkish word, then with another real Turkish word. Their task was to indicate whether the two presented words were from the same semantic category. The recognition test results showed high accuracy, implying successful learning, with no differences among TVH conditions. The SJT results were modulated by both the novelty of the words (pseudowords vs. real words) and the harmony conditions in both behavioral and ERP measures. Specifically, harmonious words lead to N400 responses similar to real words, with no such effect on the disharmonious words. These results suggest that the phonological rules of participants’ native language had an impact on semantic consolidation.
Open Access
Sporda kurumsal sürdürülebilirlik ve ERP sistemi (Fenerbahçe Spor Kulübü örneği)
(Ankara Üniversitesi, 2016) Aydın-Ayas, S.; Aydın, Umut Can
Bu araştırmanın amacı sporda kurumsal sürdürülebilirlik ve ERP (Enterprise Resource Planning) sisteminin spor sektöründe uygulanabilirliğinin ortaya konulmasıdır. Bu amaçla literatür taraması yapılmış ve Türkiye'de ERP sistemini uygulayan ilk kulüp olması nedeniyle Fenerbahçe Spor Kulübü Derneği örnek alınmıştır. Fenerbahçe Spor Kulübü Derneği'nin Kurumsal Sürdürülebilirlik çalışmaları ve ERP sisteminin modülleri incelenmiştir.Spor sektöründe kurumsal sürdürülebilirlik ve ERP sisteminin spor sektörüne uygulaması sonucunda kulüplerin maliyet tasarrufu, verimlilik artışı, bilginin tek noktadan üretilmesi ve raporlanması, yöneticiler için güvenilir ve esnek karar destek sistemi oluşturulması, katma değer yaratma gibi kazanımlar elde ettiği görülmüştür.
Open Access
The interplay of prior information and motion cues in resolving visual ambiguity in agent perception
(2023-08-06) Elmas, Sena Er
Agent perception, a complex cognitive task that involves interpreting an agent’s actions to infer their internal states and adjust our behavior accordingly, is a fundamental aspect of human cognition. Despite its importance, a significant gap persists in our understanding of how low-level factors, such as motion and form information, interact with top-down factors, such as prior information about the agents. To address this gap, we conducted two electroencephalogram (EEG) experiments investigating the interplay of prior knowledge and motion information on the temporal dynamics of agent perception in the human brain. We used human, android and robot agents engaged in various actions. The chosen agents were designed to form a set wherein form information alone could not easily resolve the ambiguity in agent identities. In the first experiment, participants were informed about agent identities be-fore the experiment (Prior Experiment), while in the second experiment, participants remained uninformed (Naive Experiment). We controlled the availability of motion information by presenting stimuli in either video and image formats. We recorded scalp EEG and utilized event-related potential (ERP) analysis and model-based representational similarity analysis (RSA) to uncover the temporal course of agent representation in the human brain. Our results revealed that the processing of agents in EEG depends on the availability of motion information and prior information. Specifically, in the Naive Experiment, agent information was available longer during the still condition than in the moving condition. In contrast, agent information was present for similar durations in still and moving conditions of the Prior Experiment. These findings suggest that prior knowledge and motion information interactively modulate the duration of the processing of agent information. Our results underscore the critical role of prior knowledge and motion cues in shaping the processing of agent information, highlighting the complex interplay between top-down modulation and bottom-up cues in driving the perception of agents and their actions. This study contributes to our understanding of the temporal dynamics of agent perception and the role of top-down and bottom-up processes in this complex cognitive task.