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Host: Gaia Scerif

Prof Luis Fuentes

University of Murcia

University of Oxford

Network Interactions in the Attentional System: Inhibition in the Spatial and Semantic Domains

Abstract: Inhibitory mechanisms play a crucial role in selecting relevant information. One of these mechanisms involves inhibition of previously attended locations, which has been referred to as inhibition of return (IOR). The early work on IOR assessed the questions of when IOR occurs, and what mechanisms explain better the phenomenon, but the question of how processing is affected at locations subject to IOR has been explored to a lesser extent. In order to assess how IOR affects processing, we have combined IOR procedures with experimental paradigms sensitive to particular levels of stimulus processing, such as semantic priming and flanker interference. The studies revealed that stimuli presented at locations subject to IOR are fully processed, but a kind of “inhibitory tagging” (IT) mechanism would disconnect temporarily activated representations of those stimuli from their associated responses. In follow-up studies we and other colleagues have assessed the locus of IT, the attributes of inhibited stimuli that undergo the temporal disconnection, and the brain circuitry involved in both IOR and IT through the testing of patients with different attentional pathology, as well as through the use of neuroimaging techniques. The main results suggest that IT is a short-lasting phenomenon that takes place at a rather late stage of processing; operates on relevant or irrelevant but prepotent attributes of inhibited stimuli, it depends on the integrity of the left dorsolateral prefrontal cortex, and is affected in patients with alterations in the executive attentional network (e.g., schizophrenic patients). In contrast, IOR is affected in parietal damage patients, suggesting an involvement of the orienting attentional network. All these findings support the idea that IOR and IT are two inhibitory mechanisms that co-operate together to bias the organisms to explore novel locations and/or objects.