At the outset of the experiment, each participant completed a 15 min training session, which was followed by the hour-long EEG testing session. Participants completed 190 trials on average (range 128–231). Trials were grouped into blocks, each containing six trials: two trials in which the position of the package did not change, two involving type E jumps, and two type D jumps. The order in which trials of a particular type occurred
was pseudorandom within a block. Participants were given an opportunity to rest for a brief period between task blocks. GS-1101 in vitro EEG data were recorded using Neuroscan (Charlotte, NC) caps with 128 electrodes and a Sensorium (Charlotte, VT) EPA-6 amplifier. The signal was sampled at 1000 Hz. All data were referenced online to Idelalisib price a chin electrode, and after excluding bad channels were rereferenced to the average signal across all remaining channels (Hestvik et al., 2007). EOG data were recorded using
a single electrode placed below the left eye. Ocular artifacts were detected by thresholding a slow-moving average of the activity in this channel, and trials with artifacts were not included in the analysis. Less than four trials per subject matched this criterion and were excluded from the analysis (less than two per condition). Epochs of 1000 ms (200 ms baseline) were extracted from each trial, time locked to the package’s change in position. The mean level of activity during the baseline interval was subtracted from each epoch. Trials containing type D jump were separated from trials containing jumps of type E, and ERPs were computed for each condition and participant by averaging the corresponding epochs. The ERPs shown in Figure 3 (main text) were computed by averaging across participants. The PPE effect was quantified in electrode Cz (following Holroyd and Coles, 2002). The PPE effect was quantified for each subject by taking the mean voltage during the time window from 200 to 600 ms following
each jump, for the two jump types. A one-tailed paired t test was used to evaluate the hypothesis that type D jumps elicited a more negative potential than type E jumps. For comparability with previous studies, topographic plots are shown for electrodes FP1, FP2, AFz, F3, Fz, F4, FT7, FC3, FCz, FC4, FT8, T7, C3, Cz, C4, T8, TP7, CP3, CPz, CP4, TP8, P7, P3, Pz, P4, P8, O1, Oz, and O2 (as MYO10 in Yeung et al. [2005], F7 and F8 were an exception, given that the used cap did not have these electrode locations). Participants were recruited from the university community and all gave their informed consent. For the first fMRI experiment, 33 participants were recruited (ages 18–37 years, M = 21.2, 20 males, all right handed). Three participants were excluded: two because of technical problems and one who was unable to complete the task in the available time. For the second experiment, 15 participants were recruited (ages 18–25 years, M = 20.5, 11 males, all were right handed).
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