title: Left middle temporal and inferior frontal regions contribute to speed of lexical decision: a TMS study.
abstract: Activation of left anterior inferior frontal gyrus (aLIFG) and left middle temporal gyrus (LMTG) has been observed in some functional neuroimaging studies of lexical decision but not others. It is thus unclear whether these two regions are necessary for word recognition. By applying continuous theta-burst transcranial magnetic stimulation (TMS) which temporally suppresses local brain function, we examined whether aLIFG and LMTG play causal roles in word recognition in a visual lexical decision task (LDT). Furthermore, we manipulated stimulus onset asynchrony (SOA) between prime and target to test whether these regions contribute to word recognition differently. In the LDT task, target words were preceded by semantically related primes (Related Condition; RC) or semantically unrelated words (Unrelated Condition; UC), under both short (150 ms) and long (600 ms) SOA conditions. TMS of aLIFG and LMTG significantly affected the word recognition speed compared to TMS of Vertex. Our results provide evidence that both aLIFG and LMTG contribute to word recognition speed. Furthermore, at short SOA, TMS of aLIFG or LMTG prolonged reaction time (RT). In contrast, at long SOA, there was a significant region by SOA by TMS interaction such that TMS of aLIFG prolonged RT, whereas TMS of LMTG speeded RT. These results suggest that aLIFG and LMTG may play different roles in word recognition.
authors.affiliation: Center for the Study of Applied Psychology, South China Normal University, Guangzhou 510631, China; Department of Anatomy and Neurobiology, University of Kentucky Medical Center, Lexington, KY 40536, USA.
authors.forename: Zude
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Department of Anatomy and Neurobiology, University of Kentucky Medical Center, Lexington, KY 40536, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Gold
authors.affiliation: Institute of Cognitive Neuroscience, National Central University, Jhongli 320, Taiwan.
authors.forename: Chi-Fu
authors.initials: CF
authors.lastname: Chang
authors.affiliation: Center for the Study of Applied Psychology, South China Normal University, Guangzhou 510631, China. Electronic address: suipingscnu@gmail.com.
authors.forename: Suiping
authors.initials: S
authors.lastname: Wang
authors.affiliation: Institute of Cognitive Neuroscience, National Central University, Jhongli 320, Taiwan. Electronic address: chijuan@cc.ncu.edu.tw.
authors.forename: Chi-Hung
authors.initials: CH
authors.lastname: Juan
mesh_terms: D000328:Adult; D001931:Brain Mapping; D003657:Decision Making / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Left anterior inferior frontal gyrus; Left middle temporal gyrus; TMS; Word recognition