Browsing by Subject "Visual adaptation"

Now showing 1 - 3 of 3

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
Size aftereffect is non-local
(Elsevier, 2020) Altan, Ecem; Boyacı, Hüseyin
It is well known that prolonged exposure to a certain size stimulus alters the perceived size of a subsequently presented stimulus at the same location. How the rest of the visual space is affected by this size adaptation, however, has not been systematically studied before. Here, to fill this gap in literature, we tested size adaptation at the adapter location as well as the rest of the visual space. We used peripherally presented solid discs (Experiment 1) and rings (Experiment 2) as adapter and target (test) stimuli. Observers adapted to a mid-sized stimulus and judged the size of the subsequently presented smaller or larger target stimuli. Results showed that the perceived sizes of target stimuli were repelled away from the adapter size, not only at the adapter location but also at other locations. These findings demonstrate that size adaptation causes widespread distortion of the visual space and alters perceived size. We discuss possible computational models that may underpin the perceptual effect.
Open Access
The spatial extent of size adaptation effect in peripheral vision
(2019-07) Altan, Ecem
It has been shown that prolonged exposure to a certain object size (i.e. size adaptation) alters the subsequent size perception such that the size of the latter appears more dissimilar to the adapted size (Pooresmaeili, Arrighi, Biagi, & Morrone, 2013). However, how much of the visual space is in uenced by the size adaptation at a certain location remains unanswered. Here, in order to investigate the spatial extent of the adaptation effect, we tested the size adaptation effect at the adapted location and various non-adapted locations. In the first psychophysical experiment, we showed a mid-sized adapter stimulus and tested its in uence on subsequent size perception at 5 locations. Results showed that the size perception at non-adapted locations was in uenced by the adapter, although not as much as the effect at the adapted location. In the second experiment, we tested the size aftereffect at 15 different locations and mapped out the perceived size distortions over the visual field. Lastly, in the third experiment, we tested the effect of size adaptation with ring-shaped stimuli and found a substantially large effect just as in the second experiment. These findings overall suggest that the size adaptation does not only have a local effect but also the size perception in consequence of adaptation is being distorted throughout the visual field.