Abstract
Adapting to the duration of a visual stimulus causes the perceived duration of a subsequently presented stimulus with a slightly different duration to be skewed away from the adapted duration. This pattern of repulsion following adaptation is similar to that observed for other visual properties, such as orientation, and is considered as evidence for duration-selective channels (Heron, et al. 2012). Here, we investigated the spatial selectivity of these duration channels by varying the distance between adaptation and test stimulus. Observers were presented with a 100 repetitions of a Gaussian blob (σ = 0.75°) located 8° above a central fixation cross, lasting either 160 or 640 ms. Following adaptation, participants completed a duration comparison task with each trial starting with four top-ups followed by the presentation of an auditory reference (320 ms) and a visual test stimulus. The duration of the visual test stimulus was varied using a staircase procedure to obtain the point of subjective equality. To investigate the spatial extent of the adaptation effect, the distance between adaptation and test stimuli was varied between 0° to 15° with the stimuli always presented at an eccentricity of 8°. Our results show a clear duration adaptation effect: the test stimulus was perceived to have a longer duration following adaptation to a shorter duration, and a shorter duration following adaptation to a longer duration. Importantly, this adaptation effect occurred at all measured distances, and there was no evidence for a decrease in the strength of adaptation at larger distances. We conclude that duration adaptation is position-invariant, transferring to locations separated by more than 10° from the location of the adaptation stimulus. Given the spatial extent of the adaptation effect, it seems unlikely that the proposed duration channels are represented in lower level retinotopically organized visual areas, instead suggesting a later locus.
Meeting abstract presented at VSS 2016