TY - JOUR
T1 - Dissociating Parieto-Frontal Networks for Phonological and Semantic Word Decisions
T2 - A Condition-and-Perturb TMS Study
AU - Hartwigsen, Gesa
AU - Weigel, Anni
AU - Schuschan, Paul
AU - Siebner, Hartwig R
AU - Weise, David
AU - Classen, Joseph
AU - Saur, Dorothee
N1 - © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: [email protected].
PY - 2016/6
Y1 - 2016/6
N2 - Left posterior inferior frontal gyrus (pIFG) and supramarginal gyrus (SMG) are key regions for phonological decisions, whereas angular gyrus (ANG) and anterior IFG (aIFG) are associated with semantics. However, it is less clear whether the functional contribution of one area changes in the presence of a dysfunctional area within the network. Using repetitive transcranial magnetic stimulation (rTMS), we first tested whether perturbing one area would disrupt behavior. Second, we applied a condition-and-perturb approach, combining parietal offline rTMS with frontal online rTMS to investigate how the functional contribution of a frontal region changes in the presence of a dysfunctional parietal region. We found that rTMS over SMG or pIFG delayed phonological decisions, but this was not enhanced by combining supramarginal rTMS with pIFG rTMS. In contrast, semantic decisions were only impaired when angular rTMS was combined with aIFG rTMS. We infer that offline rTMS caused a dysfunction of ANG which increased the functional relevance of aIFG for semantic decisions and sensitized this network to the disruptive effects of aIFG rTMS. The results provide causal evidence that ANG and aIFG contribute to semantics and that the functional significance of one area within this network depends on the functional integrity of the other.
AB - Left posterior inferior frontal gyrus (pIFG) and supramarginal gyrus (SMG) are key regions for phonological decisions, whereas angular gyrus (ANG) and anterior IFG (aIFG) are associated with semantics. However, it is less clear whether the functional contribution of one area changes in the presence of a dysfunctional area within the network. Using repetitive transcranial magnetic stimulation (rTMS), we first tested whether perturbing one area would disrupt behavior. Second, we applied a condition-and-perturb approach, combining parietal offline rTMS with frontal online rTMS to investigate how the functional contribution of a frontal region changes in the presence of a dysfunctional parietal region. We found that rTMS over SMG or pIFG delayed phonological decisions, but this was not enhanced by combining supramarginal rTMS with pIFG rTMS. In contrast, semantic decisions were only impaired when angular rTMS was combined with aIFG rTMS. We infer that offline rTMS caused a dysfunction of ANG which increased the functional relevance of aIFG for semantic decisions and sensitized this network to the disruptive effects of aIFG rTMS. The results provide causal evidence that ANG and aIFG contribute to semantics and that the functional significance of one area within this network depends on the functional integrity of the other.
U2 - 10.1093/cercor/bhv092
DO - 10.1093/cercor/bhv092
M3 - Journal article
C2 - 25953770
SN - 1047-3211
SP - 2590
EP - 2601
JO - Cerebral Cortex
JF - Cerebral Cortex
M1 - bhv092
ER -