Illustration of the experimental procedure.

<p>A, Practice phase I. B, Practice phase ii. C, the formal experiment. The ERP data were collected in response to the 1000-Hz tones with 1.5- and 2.5-s durations. D, the five attentional cues used in this study.</p

sLORETA images of the standardized current density maximum in the T vs. the P attention conditions.

<p>A, the results at the time interval of P2 (180-220 ms). B, the results at the time interval of CNV (800-1600 ms). The color scale is equal in all the maps, of which the strongest activations are indexed in yellow.</p

Distribution of ERP measurements in different attention conditions (data are collected at the electrode of FCz).

<p>A, the distribution of P2 amplitudes. The three horizontal lines in every box reflect the lower quartile (25%), median (50%), and upper quartile (75%) of the P2 amplitudes (refer to the legend of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066190#pone-0066190-g002" target="_blank">Figure 2</a> for more details). B, the distribution of CNV amplitudes. C, the average and 95% confidential interval (CI) of the ERPs in response to the 1.5-s tone. For the sake of brevity, only the ERPs in the T and the P conditions are displayed. D, the average and 95% CI of the ERPs in response to the 2.5-s tone.</p

Grand-mean ERP waveforms and topographies of the P2 and CNV components.

<p>A, the P2 topography at 180-220 ms post-stimuli. B: the CNV topography at 800-1600 ms post-stimuli. C, the ERP waveforms (at FCz electrode site) in response to the 1.5-s tone. D, the ERP waveforms (at FCz electrode site) in response to the 2.5-s tone.</p

Behavioral results.

<p>A, the measurements of reaction time (RT) and accurate rate (ACC) in time discrimination task. B, the RT in pitch discrimination task. Shown are the boxplots of medians of RT and ACC in different attention modulation conditions. The three horizontal lines in every box reflect the lower quartile (25%), median (50%), and upper quartile (75%) of the statistics, respectively. The whisker is equal to one interquartile range of the statistics. The “+” marks represent outliers outside of the whisker.</p