The SOA between prime and target was 300 msec. The use of a short SOA between
prime and target (300 msec) ensures to reduce the risk of semantic expectancies (i.e., creation of a mental list of potential associates). The intertrial interval (ITI) separating the single trials varied between 2000 msec and 2000 msec plus one repetition time (TR; here TR = 2.37 sec) to increase the sampling rate of the blood oxygenation level-dependent (BOLD) response (Josephs et al. 1997). The stimuli were presented visually via projection to a mirror directly above the participant’s head at eye level. The experimental procedure was programmed Inhibitors,research,lifescience,medical using the software presentation (Neurobehavioral Systems, http://www.neurobs.com). Figure 1 Timing (in milliseconds) used in each experimental trial of Experiment 1 (semantic categorization [SC]) and Experiment 2 (silently SRT1720 clinical trial thinking about a word’s meaning [SilTh]). Critically, Experiments 1 and Inhibitors,research,lifescience,medical 2 differed with respect to the linguistic task. However, a linguistic task involving a binary decision was used in Experiment 1 (i.e., semantic categorization), a linguistic “task” that did not require a binary decision was used in Experiment 2 (i.e., silently thinking about a word’s meaning). Experiment 1: semantic categorization Participants were asked to decide whether Inhibitors,research,lifescience,medical each
item presented in capital letters (i.e., the second word of each trial) was natural or manmade (i.e., semantic categorization). For the symbol pairs, participants indicated whether the series of symbols were identical or different. Participants responded using their left hand. Half of the participants (n = 9) used the forefinger for the response “natural” and the Inhibitors,research,lifescience,medical middle finger for the response “manmade” and the other half (n = 9) used the reversed pattern. The first session was preceded by a short practice session of 12 items
before scanning started. Inhibitors,research,lifescience,medical Practice was repeated until participants responded without errors. Experiment 2: silently thinking about a word’s meaning In the related, unrelated, neutral, and filler conditions, the trial timing was identical to the one used in Experiment 1 except for the presentation duration of the target Dichloromethane dehalogenase word. The written target word was presented in capital letters for 300 msec followed by a blank screen for 1500 msec. The same timing was applied for the presentation of symbol pairs. As in Experiment 1, the prime word was replaced by a blank screen for 200 msec in the neutral and symbol trials. All other parameters (i.e., SOA, variable ITI) and the software used for stimulus presentation were equivalent to Experiment 1. In Experiment 2, inspired by Chee et al. (2003), participants were instructed to read each uppercase target-word silently and to think of its meaning (i.e., deeply process its semantic properties). Participants performed the semantic processing from the onset of the target until the next trial started.