Article: Timing the path to perception
- Timing the path to perception
Study shows how brain events in 'attentional blink' relate to consciousness
By Ishani Ganguli
The sooner a person becomes conscious of an image, the more likely it is that a second image shown shortly thereafter will be seen, according to a study this week in Nature Neuroscience.
The research takes "new ideas about how consciousness might work in the brain and show[s] that it actually works" by "very closely link[ing]. behavior to brain activity at different points in time in the brain," James Enns at the University of British Columbia in Vancouver, who did not participate in the study, told The Scientist.
The French research team used these methods to develop a complete cascade of brain events associated with attentional blink-the difficulty of perceiving the second of two targets presented within a half-second of the first. The paradigm addresses the mechanism of how much can enter your awareness, said Justin Feinstein at the University of Iowa, who did not participate in the study.
Among various explanations for attentional blink, a common view is that both targets enter a first stage of nonconscious processing, then the second target may be denied access to a subsequent, conscious processing stage with limited capacity, coauthor Claire Sergent at Institut National de la Santé et de la Recherche Médicale in Orsay, France, told The Scientist.
In their model of attentional blink, the authors used two word targets (T1 and T2) inserted in short succession into a stream of distracting images on a screen. Their previous work with this model suggested that seeing the second target in attentional blink is an all-or-none phenomenon; subjects either saw it fully or did not see it at all, even though they were asked to rate visibility.
In order to investigate the neurological basis of this bimodal distribution, the team measured event-related potentials (ERPs) to chart the time course of the brain's response. To isolate those ERP readings invoked specifically by the second word, they subtracted the readings obtained when T2 was replaced by a blank screen. They found that waves correlated with early visual processing, P1 and N1, were preserved whether or not the subject had reported seeing the second stimulus.
Full Text at TheScientist
Robert Karl Stonjek
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