Contralateral preference of activated voxels during easy and difficult search conditions.

<p>Contralateral preference visualized by t-tests for all voxels activated by easy search and difficult search conditions (p<0.005, RFX, cluster threshold: 50 mm²). The color convention and the significance level for hemifield preference are described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003167#pone-0003167-g002" target="_blank">Fig. 2</a>. (a) Histograms with t-values for all activated voxels within predefined ROIs of the dorsal FPN. The range of t-values represented by each bar is 1.13. The significance level (p<0.05) for contralateral preference to the left (−) or right (+) is indicated by black lines on the x-axis of each histogram. As in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003167#pone-0003167-g002" target="_blank">Figure 2</a>, the percentage of voxels with a significant contralateral preference for the left or right hemifield is given on the appropriate side of the histograms. (b) Dorsal posterior view of the flattened left and right hemisphere with representation of t-values on the surface. (c) Histograms with t-values for all activated voxels within control ROIs MC (motor cortex) and VO (visual occipital). T: mean t-value of activated voxels; STD: standard deviation of t-values; Yellow dotted lines: predefined anatomical ROIs.</p

Contralateral preference of activated voxels during spatial orienting (SO) and visual search (VS).

<p>Contralateral preference visualized by t-tests for all voxels activated by SO and VS (p<0.005, RFX, cluster threshold: 50 mm²). Negative (red) and positive (blue) t-values indicate a preference for the left and right hemifield, respectively. Voxels with t-values<−2.26 or >2.26 show a significant contralateral preference (p<0.05) and are indicated by dark blue or red, respectively. White color indicates voxels involved in the process with no preference for either hemifield. (a) Histograms with t-values for all activated voxels within predefined ROIs of the dorsal FPN. The range of t-values represented by each bar is 1.13. The significance level (p<0.05) for contralateral preference to the left (−) or right (+) is indicated by black lines on the x-axis of each histogram. Additionally, the percentage of voxels with a significant contralateral preference for the left or right hemifield is shown on the appropriate side of the histograms. (b) Dorsal posterior view of the flattened left and right hemisphere with representation of t-values on the surface. (c) Histograms with t-values for all activated voxels within control ROIs MC (motor cortex) and VO (visual occipital). T: mean t-value of activated voxels; STD: standard deviation of t-values; Yellow dotted lines: predefined anatomical ROIs.</p

Summary of behavioral results.

<p>Reaction times (RT), error rates (ER), target detection sensitivity (d') and the response criterion (c) for visual search in the left and right hemifield, comparison of easy and difficult search conditions and comparison of the behavioral data of the left and right hemifield during easy and difficult search conditions. Data shown ± standard errors.</p

Paradigm separating spatial orienting (SO) and visual search (VS).

<p>After a fixation period, a central cue indicated the relevant hemifield for the next trial. When stimuli appeared, subjects had to search covertly for a target line among the 6 positions of the cued hemifield. Task difficulty was modified by the number of distractors with nonvertical orientations in the relevant hemifield (easy: 2; difficult: 5).</p

Activated voxels in the left and right ROIs of the FPN during spatial orienting (SO) and visual search (VS).

<p>Anatomically defined ROI sizes (1 mm×1 mm×1 mm voxels); Percentage (%) of activated voxels during spatial orienting (SO) and distinct visual search (VS) conditions.</p