Combining temporal and spectral information with spatial mapping to identify differences between phonological and semantic networks : a magnetoencephalographic approach

McNab, Fiona; Hillebrand, Arjan; Swithenby, Stephen and Rippon, Georgina (2012). Combining temporal and spectral information with spatial mapping to identify differences between phonological and semantic networks : a magnetoencephalographic approach. Frontiers in Psychology, 3 (AUG),

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Official URL: http://www.frontiersin.org/Language_Sciences/10.33...

Abstract

Early, lesion-based models of language processing suggested that semantic and phonological processes are associated with distinct temporal and parietal regions respectively, with frontal areas more indirectly involved. Contemporary spatial brain mapping techniques have not supported such clear-cut segregation, with strong evidence of activation in left temporal areas by both processes and disputed evidence of involvement of frontal areas in both processes. We suggest that combining spatial information with temporal and spectral data may allow a closer scrutiny of the differential involvement of closely overlapping cortical areas in language processing. Using beamforming techniques to analyze magnetoencephalography data, we localized the neuronal substrates underlying primed responses to nouns requiring either phonological or semantic processing, and examined the associated measures of time and frequency in those areas where activation was common to both tasks. Power changes in the beta (14–30 Hz) and gamma (30–50 Hz) frequency bands were analyzed in pre-selected time windows of 350–550 and 500–700 ms In left temporal regions, both tasks elicited power changes in the same time window (350–550 ms), but with different spectral characteristics, low beta (14–20 Hz) for the phonological task and high beta (20–30 Hz) for the semantic task. In frontal areas (BA10), both tasks elicited power changes in the gamma band (30–50 Hz), but in different time windows, 500–700 ms for the phonological task and 350–550 ms for the semantic task. In the left inferior parietal area (BA40), both tasks elicited changes in the 20–30 Hz beta frequency band but in different time windows, 350–550 ms for the phonological task and 500–700 ms for the semantic task. Our findings suggest that, where spatial measures may indicate overlapping areas of involvement, additional beamforming techniques can demonstrate differential activation in time and frequency domains.

Item Type:Article
Additional Information:© 2012 McNab, Hillebrand, Swithenby and Rippon. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
Uncontrolled Keywords:magnetoencephalography, beamforming, semantic processing, phonological processing, gamma, beta, synthetic aperture magnetometry, Psychology(all)
Divisions:Schools_of_Study > Life & Health Sciences > Psychology (LHS)
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ID Code:17379
Deposited By:Prof Alfred Admin
Deposited On:31 Aug 2012 10:48
Last Modified:25 Sep 2014 08:59

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