Electrophysiological signatures of temporal segregation and integration of visual information an MEG study
56.454, Tuesday, May 14, 2:45 - 6:45 pm, Orchid Ballroom
Andreas Wutz1, Nathan Weisz1, David Melcher1; 1Center for Mind and Brain Sciences (CIMeC), University of Trento, Italy
The balance between temporal segregation and integration of incoming sensory information constitutes a functional necessity of visual information processing. Whereas segregation establishes discrete temporal entities and therefore allows for an effective read-out of information at one particular instant, it is also critical to integrate and accumulate sensory input over time to preserve perceptual continuity. We operationalized temporal segregation and integration using a forward masking procedure with a variable stimulus onset asynchrony (SOA), while observers performed an enumeration task. Concurrently, we recorded electrophysiological brain activity using MEG in order to map the neuronal time course prior and in response to these two intrinsically temporal mechanisms. Enumeration is a particularly interesting task in this context, as it has previously been shown that its capacity critically depends upon the amount of temporal integration between two successive visual displays. The target items were physically identical to the mask elements and were presented superposed upon the masking pattern, such that an improvement in enumeration performance with increasing SOA indicated observers ability to temporally segregate the onset of mask and target displays. Along these lines, we hypothesized that correct trials indicate temporal segregation, whereas incorrect trials are associated with temporal integration of mask and target information. In pre- and peri-stimulus intervals alpha-to-beta oscillatory power was higher in temporal integration trials. This effect originated from occipital and temporal generators. Temporal segregation evoked a stronger visual response time-locked to the masking pattern with a widespread, mostly left hemispheric occipito-parietal topography. Relating these two effects around (pre-, peri- and post) stimulus onset within a single-trial analysis reveals the electrophysiological circumstances under which visual operations create discrete temporal windows over which sensory information is accumulated.