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Antonino Raffone
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Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2014) 26 (5): 1168–1179.
Published: 01 May 2014
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Global workspace access is considered as a critical factor for the ability to report a visual target. A plausible candidate mechanism for global workspace access is coupling of slow and fast brain activity. We studied coupling in EEG data using cross-frequency phase–amplitude modulation measurement between delta/theta phases and beta/gamma amplitudes from two experimental sessions, held on different days, of a typical attentional blink (AB) task, implying conscious access to targets. As the AB effect improved with practice between sessions, theta–gamma and theta–beta coupling increased generically. Most importantly, practice effects observed in delta–gamma and delta–beta couplings were specific to performance on the AB task. In particular, delta–gamma coupling showed the largest increase in cases of correct target detection in the most challenging AB conditions. All these practice effects were observed in the right temporal region. Given that the delta band is the main frequency of the P3 ERP, which is a marker of global workspace activity for conscious access, and because the gamma band is involved in visual object processing, the current results substantiate the role of phase–amplitude modulation in conscious access to visual target representations.
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2001) 13 (6): 766–785.
Published: 15 August 2001
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Luck and Vogel (1997) showed that the storage capacity of visual working memory is about four objects and that this capacity does not depend on the number of features making up the objects. Thus, visual working memory seems to process integrated objects rather than individual features, just as verbal working memory handles higher-order “chunks” instead of individual features or letters. In this article, we present a model based on synchronization and desynchronization of reverberatory neural assemblies, which can parsimoniously account for both the limited capacity of visual working memory, and for the temporary binding of multiple assemblies into a single pattern. A critical capacity of about three to four independent patterns showed up in our simulations, consistent with the results of Luck and Vogel. The same desynchronizing mechanism optimizing phase segregation between assemblies coding for separate features or multifeature objects poses a limit to the number of oscillatory reverberations. We show how retention of multiple features as visual chunks (feature conjunctions or objects) in terms of synchronized reverberatory assemblies may be achieved with and without long-term memory guidance.