Browsing by Author "Kafaligonul, Hulusi"

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Open Access
Behavioral and ERP evidence that object-based attention utilizes fine-grained spatial mechanisms
(2022-06) Catak, Esra N.; Özkan, M.; Kafaligonul, Hulusi; Stoner, G. R.
Valdes-Sosa, Cobo, and Pinilla (1998) introduced a transparent-motion design that provided evidence of object-based attention whereby attention embraces all features of an attentionally cued perceptual object including new unpredictable features such as a brief translation. Subsequent studies using variants of that design appeared to provide further behavioral, electrophysiological, and brain imaging evidence of object-based attention. Stoner and Blanc (2010) observed, however, that these previous results could potentially be explained by feature-based competition/normalization models of attention. To distinguish between the object-based and feature-based accounts, they introduced “feature swaps” into a delayed-onset variant of the transparent-motion design (Reynolds, Alborzian, & Stoner, 2003). Whereas the object-based attention account predicted that the effect of cueing would survive these feature swaps, the motion-competition account predicted that the effect of cueing would be reversed by these feature swaps. The behavioral results of Stoner and Blanc (2010) supported the object-based account, and in doing so, provided evidence that the attentional advantage in this design is spatially selective at the scale of the intermixed texture elements (i.e., dots) of the overlapping and moving dot fields. In the present study, we used the design of Stoner and Blanc (2010) to investigate both psychophysical performance and evoked activities under different cueing and feature swapping conditions. We confirmed that the behavioral effects of attentional cueing survived feature swaps and found event-related potential (ERP) correlates of those effects in the N1 component range over occipital and parieto-occipital scalp sites. These modulations of the neural activity were, moreover, significantly associated with variation in behavioral performance values across the different conditions. Our findings thus provide the first evidence of the role of the N1 component in object-based attention in this transparent-motion design under conditions that rule out feature-based mechanisms and that reveal selective processing at a fine spatial scale.
Open Access
The involvement of centralized and distributed processes in sub-second time interval adaptation: an ERP investigation of apparent motion
(Blackwell Publishing Ltd, 2017) Kaya, Utku; Yildirim, Fazilet Zeynep; Kafaligonul, Hulusi
Accumulating evidence suggests that the timing of brief stationary sounds affects visual motion perception. Recent studies have shown that auditory time interval can alter apparent motion perception not only through concurrent stimulation but also through brief adaptation. The adaptation after-effects for auditory time intervals was found to be similar to those for visual time intervals, suggesting the involvement of a central timing mechanism. To understand the nature of cortical processes underlying such after-effects, we adapted observers to different time intervals using either brief sounds or visual flashes and examined the evoked activity to the subsequently presented visual apparent motion. Both auditory and visual time interval adaptation led to significant changes in the ERPs elicited by the apparent motion. However, the changes induced by each modality were in the opposite direction. Also, they mainly occurred in different time windows and clustered over distinct scalp sites. The effects of auditory time interval adaptation were centred over parietal and parieto-central electrodes while the visual adaptation effects were mostly over occipital and parieto-occipital regions. Moreover, the changes were much more salient when sounds were used during the adaptation phase. Taken together, our findings within the context of visual motion point to auditory dominance in the temporal domain and highlight the distinct nature of the sensory processes involved in auditory and visual time interval adaptation. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd
Open Access
Neural correlates of metacontrast masking across different contrast polarities
(Springer, 2021) Aydin, Alaz; Ogmen, H.; Kafaligonul, Hulusi
Metacontrast masking is a powerful illusion to investigate the dynamics of perceptual processing and to control conscious visual perception. However, the neural mechanisms underlying this fundamental investigative tool are still debated. In the present study, we examined metacontrast masking across diferent contrast polarities by employing a contour discrimina tion task combined with EEG (Electroencephalography). When the target and mask had the same contrast polarity, a typical U-shaped metacontrast function was observed. A change in mask polarity (i.e., opposite mask polarity) shifted this masking function to a monotonic increasing function such that the target visibility was strongly suppressed at stimulus onset asyn chronies less than 50 ms. This transition in metacontrast function has been typically interpreted as an increase in intrachannel inhibition of the sustained activities functionally linked to object visibility and identity. Our EEG analyses revealed an early (160–300 ms) and a late (300–550 ms) spatiotemporal cluster associated with this efect of polarity. The early cluster was mainly over occipital and parieto-occipital scalp sites. On the other hand, the later modulations of the evoked activities were centered over parietal and centro-parietal sites. Since both of these clusters were beyond 160 ms, the EEG results point to late recurrent inhibitory mechanisms. Although the fndings here do not directly preclude other proposed mechanisms for metacontrast, they highlight the involvement of recurrent intrachannel inhibition in metacontrast masking