The three-condition oddball task (see below) was conducted

during the EEG session on the third day. Experimental paradigm All stimuli were presented on a computer monitor using the E-prime software system (Psychology Software Tools Inc., Pittsburgh, PA). Stimuli were presented on a black screen for 200 msec, followed by a delay varying between 1000 and 1100 msec before the next stimulus. Three different types of visual stimuli were presented: (1) standard nontarget stimuli, a small hollow white square; (2) target stimuli, a small Inhibitors,research,lifescience,medical white X; and (3) novel rare nontarget stimuli, different shapes of various colors. Participants responded with the index finger of their dominant hand and were instructed to press a response box button only when they saw target stimuli. Stimuli were presented in a predetermined order, with standard stimuli appearing 210 times, target stimuli appearing 35 times, and rare nontarget stimuli appearing 35 times over approximately Inhibitors,research,lifescience,medical 6.5 min. Each participant was shown an example of Inhibitors,research,lifescience,medical the target stimulus before the task began. EEG acquisition and analysis EEG was acquired using a 64-channel system that used the SynAmps2 amplifier and Scan 4.3 acquisition software (Compumedics Neuroscan Inc., Charlotte, NC). The EEG signal was referenced to an

electrode located between Cz and CPz for online recording, and then re-referenced to the right ear offline. The ground electrode was placed 8 cm above the nasion. Electrode impedances were maintained below 10 kOhms. The SynAmps2 amplifier had a fixed range of ±333 μV sampled with a 24-bit A/D converter

where the least significant bit was 0.019 μV. The sampling rate was 250 samples/sec. EEG recordings were processed offline Inhibitors,research,lifescience,medical using the Edit program in Scan 4.3 (Compumedics Neuroscan, Inc., Charlotte, NC). Artifacts from eye movements were removed using the ocular artifact reduction Inhibitors,research,lifescience,medical algorithm (ARTCOR procedure) in Scan 4.3. Data were then band-pass filtered between 0.5 and 30 Hz using a zero-phase lag filter at 48 dB/octave. Stimulus-locked epochs for the target condition were extracted for all instances where there was a correct behavioral response. Trials consisted of 1800 msec of data, including a 500-msec prestimulus baseline. Any epochs with voltages beyond the range of ±75 μV were rejected as artifacts and excluded from further processing. In addition to the visual oddball task, 5 min of baseline eyes open resting ALOX15 EEG was recorded at the start of the session. Time-frequency measures TF measures were computed using the Cohen’s class binomial reduced interference distribution (RID) transform (see Williams 1996; Bernat et al. 2005 for more detailed descriptions), the advantage of which is that it provides a find more uniform resolution across the TF surface. TF representations were created using the entire 1800-msec epoch to minimize edge effects.