Page 46 - It' about time: Studying the Encoding of Duration

An investigation of the spatial selectivity of the duration after-effect (modulated) states to explicitly encode duration. In other words, the different after-effects might not reflect the existence of distinct mechanisms that independently encode duration, but distinct steps in the hierarchal processing of duration. The observed lack of spatial selectivity for the duration after-effect raises several questions about the selection and simultaneous processing of multiple events with different durations. During natural situations many different events 2 can occur at once leading to an overlap in the durations of different events. However, if duration information from multiple sources cannot be dissociated based on their spatial location, it is unclear how the duration processing mechanisms deal with the presentation of multiple durations. One possibility is that attentional selection plays a role in the processing of multiple durations. A study by Cheng, Yang, Han, Ding, and Fan (2014) showed that human observers are able to process up to four multiple durations at once. Furthermore, duration tracking performance dropped steadily when attention had to be spread over a larger amount of different duration stimuli. This suggests that the processing of duration information from multiple sources relies on attentional selection to bind duration information to specific objects or spatial locations. To summarize, we found a clear duration after-effect at all measured adapter-test distances. There was no evidence for a decrease in the magnitude of the duration after-effect at larger visual distances or across hemifields. We conclude that the duration after-effect does not result from adaptation occurring early on in the visual processing hierarchy. Instead, it seems likely that duration information is a high-level stimulus property that is encoded later on in the visual processing hierarchy. 45