However, neural semantic priming effects (Wheatley et al. 2005; i.e., suppression of neural activation for related compared to unrelated word pairs) and neural word repetition priming effects (Chee et al. 2003) have been reported in the LIFG with linguistic tasks that did not require a binary response, namely silent reading and silently thinking about the meaning of words. The absence of consensus between the studies of Wheatley et al. (2005), Chee et al. (2003), and Wright et al. (2011) Inhibitors,research,lifescience,medical may be due to the fact that both the paradigms (Priming vs. Word presentation) and the linguistic tasks (Silently reading vs. Passive listening) did not activate semantic DAPT research buy properties of words in the same way. In the present research, using
Inhibitors,research,lifescience,medical the same experimental design and the same linguistic materials, we compared the neural response related to lexical-semantic processing by contrasting two semantic tasks that involved either a binary decision process (i.e., semantic categorization task: natural/manmade decision; Experiment 1) or not (i.e., silently thinking about a word’s meaning;
Experiment 2). The role of the inferior frontal gyrus (IFG) in semantics was intensively investigated in the last two decades (for a review, Thompson-Schill et al. 1999; Bookheimer 2002; Noppeney et al. 2004). Activation of the LIFG is discussed as especially contributing to the processes required for semantic Inhibitors,research,lifescience,medical decision making (Demb et al. 1995; Gabrieli et al. 1998; Wagner et al. 2000; Roskies et al. 2001) and strategic semantic retrieval Inhibitors,research,lifescience,medical (Sylvester and Shimamura 2002). Semantic processing using lexical tasks involving a binary decision like the LDT, semantic judgment or categorization tasks shared activations in temporal brain areas such as the inferior
temporal gyrus (ITG), the MTG, and the STG, in the inferior parietal lobe (IPL), and particularly, in the LIFG (Demb et al. 1995; Roskies et al. 2001; Wagner et al. 2001; Kotz et al. 2002; Copland et al. 2003; Rossell et Inhibitors,research,lifescience,medical al. 2003; Giesbrecht et al. 2004; Raposo et al. 2006; Kuperberg et al. 2008; Ruff et al. 2008; Wright et al. 2011). Roskies et al. (2001) showed that brain activation during a two-choice semantic synonym task (i.e., subjects indicated whether two words had the same meaning) compared to a rhyme-judgment task was modulated within the LIFG. This task-driven activation of left inferior frontal regions was discussed as possibly subserving controlled Sitaxentan “end-stage decision processes” that interact with other brain regions like the temporal cortex to access, select, gate, or retrieve semantic information stored in the lexical entries of the mental lexicon. This interpretation is in accordance with Wu et al. (2009) suggesting activation of a separate fronto-parietal network for semantic decision making and it matches the general role of frontal regions during cognitive control processes (Duncan et al. 1996; Fuster 2001; Miller and Cohen 2001; Koechlin et al. 2003).