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Edmund Chong, Won Mok Shim; Representation of stimulus identity in apparent motion. Journal of Vision 2011;11(11):728. doi: 10.1167/11.11.728.
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© ARVO (1962-2015); The Authors (2016-present)
When a static stimulus appears at two different locations successively with some time interval in between, we perceive its motion across the two locations – the illusion of apparent motion. Previous research shows that when a target stimulus is presented on the apparent motion path such that it matches spatio-temporally with the presumed movement of the apparent motion representation, the target is easier to detect (Schwiedrzik et al., 2007). This and similar studies (Yantis and Nakama, 1998, Muckli et al., 2005) suggest that there is some representation maintained across the apparent motion path. However, it is unclear whether this representation contains stimulus specific information such as stimulus identity.
We examined this question using a target discrimination paradigm. After presenting 4–5 cycles of apparent motion across two left or two right-tilted gratings, a target (also a left or right-tilted grating) was briefly presented at the midpoint of the motion path. Subjects reported whether the orientation of the target grating matched that of the motion-inducing stimuli or not. This was contrasted with target discrimination in a flicker condition where the two gratings at different locations were flashed simultaneously instead of successively, abolishing the percept of apparent motion.
The results show that subjects are more likely to respond that the target matches the inducing stimuli for the apparent motion condition, compared to the flicker condition. Furthermore, this is accompanied by decreased target discriminability in the apparent motion condition. This increased response toward target-stimulus matching in the apparent motion condition suggests that stimulus identity is maintained in the apparent motion representation.
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