Abstract
The irrelevant speech effect illustrates that sounds that are irrelevant to a visually presented short-term memory task still interfere with neuronal function. In the present study we explore the functional and effective connectivity of such interference. The functional connectivity analysis suggested an interaction between the level of irrelevant speech and the correlation between in particular the left superior temporal region, associated with verbal working memory, and the left medial temporal lobe. Based on this psycho-physiological interaction, and to broaden the understanding of this result, we performed a network analysis, using a simple network model for verbal working memory, to analyze its interaction with the medial temporal lobe memory system. The results showed dissociations in terms of network interactions between frontal as well as parietal and temporal areas in relation to the medial temporal lobe. The results of the present study suggest that a transition from phonological loop processing towards an engagement of episodic processing might take place during the processing of interfering irrelevant sounds. We speculate that, in response to the irrelevant sounds, this reflects a dynamic shift in processing as suggested by a closer interaction between a verbal working memory system and the medial temporal lobe memory system.
Highlights
Cognitive functions are implemented in the network architecture of the brain
In a recent study (Gisselgård et al, 2003) we reported that the irrelevant speech effect was associated with a relative decrease of activation in the left superior temporal gyrus (STG) and a similar, but weaker, activity decrease in the right homotopic region (Fig. 2a)
In the first analysis of the present study, we investigated the functional connectivity of the superior temporal region where the irrelevant speech effect was expressed (Gisselgård et al, 2003) in an attempt to understand its role in verbal working memory by reanalyzing the data from our previous study of the irrelevant speech effect (Gisselgård et al, 2003)
Summary
Cognitive functions are implemented in the network architecture of the brain. It is typically hypothesized that information is represented as distributed patterns of activity in these networks and that cognitive processing emerges as a consequence of the interaction between functionally specialized brain regions (e.g., Arbib, 2003; Ingvar and Petersson, 2000; Mesulam, 1998). F.C. Donders Centre for Cognitive Neuroimaging, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands.
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