Figure 1.
Time course of the VS stimulus.
First, the fixation mark appeared on a blank screen and lasted 300 ms. Next, the 9 textured spheres faded in from the background over a 1000 ms period. Then, the spheres remained static for 1000 ms. This was followed by displaying the stimulus motion for 1000 ms, 8 spheres simulating forward observer motion and the other (target) had independent motion, forward or backward with different speeds than that o the observer. Finally, the response period, lasting 3000 ms, displayed the spheres static, four of which were labeled with numbers 1–4, one corresponding to the target. The subject's task was to chose the number corresponding to target.
Figure 2.
(A) Left hemisphere cortical activation at 230 ms of MT+ area in a representative subject. The activation shown on the inflated brain, in the cortical region, is at least 2.5 SD above noise level. (B) The corresponding time courses of MT+ activation in the same subject (top: left hemisphere; bottom: right hemisphere). The red circle indicates the peak at the 230 ms ERF corresponding to P230.
Figure 3.
Resolution matrix showing percentage signal contribution across columns of each ROI.
ROIs marked in red are joined together, ROIs in black were discarded, and ROIs in green are considered as separable regions. Abbreviations: Cinf – Inferior Central Sulcus, Csup – Superior Central Sulcus, DIPSM – Dorsal intraparietal sulcus middle, IPSsup – superior Intraparietal Sulcus, MPFC – middle Prefrontal Cortex, MT+ - human middle temporal area, PostCinf – Inferior Postcentral sulcus, SPL – Superior Parietal Lobule, FEF – Frontal Eye Field area, STP – Superior Temporal Polysensory area, STSm – Middle Superior Temporal Sulcus, VIP – Ventral Intraparietal Sulcus, V3a – area V3a.
Figure 4.
Cortical Areas in the left and right hemispheres that remained after the application of the resolution matrix.
Abbreviations: STSv: ventral part of the Superior Temporal Sulcus; STP, the Superior Temporal Polysensory area; MT+: human Middle Temporal determined with the MToc test. It includes areas MT, MST, and V6; V3a: is retinotopic area V3a that was defined through fMRI retinotopic mapping,;VIP: Ventral Intraparietal area,;IPS: Intraparietal Sulcus;, SPL: Superior Temporal Lobule,; FEF:Frontal Eye Field: and MPFC: Middle Prefrontal Cortex.
Figure 5.
Time courses of 10 Hz alpha band oscillatory power in selected ROIs.
ROIs include left (LH) and right (RH) hemispheres in Exp Only and VS (A) visual processing areas and (B) frontoparietal areas. The y-axis represents the z-score of oscillatory power. The x-axis represents time in milliseconds relative to motion onset (0 ms). The blue line shows the 10 Hz power in the Exp Only condition with 2SD error shown in blue shade around the time course. The red line shows the 10 Hz power in the VS condition with 2SD error in red shade around the time course. The black horizontal line indicates z = 0, representing the average normalized baseline power. Dotted lines indicate z = 2 and z = −2 lines.
Table 1.
10 Hz Alpha Power time periods above threshold.
Figure 6.
Wavelet power at 10 Hz in frontoparietal regions.
The x-axis represents time from stimulus motion onset and the y-axis represents the pseudo z-score alpha power in the region. The blue line illustrates activation in ipsilateral VF and the red line, activation in the contralateral VF. The shaded region indicates 2 standard errors about the mean of each time course. Dotted lines denote 0 ms and 1000 ms relative to motion onset.
Figure 7.
Weighted Phase Lag Index in select ROIs.
ROIs are seeded on (A) right hemisphere MT+, (B) left hemisphere MT+, (C) right hemisphere FEF, (D) left hemisphere FEF in the VS task normalized by the within-frequency standard error measure (SEM). The x-axis represents time and the y-axis represents pseudo z-score significance. Shaded regions indicate regions of p<0.01 cluster significance.
Figure 8.
Visual Search (VS) behavioral performance as a function of absolute object velocity over varying stimulus motion durations (1000, 500, 300, 200) milliseconds.
X-axis represents relative object velocity (cm/s) and y-axis represents performance (% correct). Error bars represent the 95 percentile confidence interval of the mean performance value. Dotted line at 25% indicates chance level. Arrow indicates observer motion velocity relative to objects (−3 cm/s). The difference between observer speed and object velocity is the relative object velocity shown in the display.
Figure 9.
Time courses of 10 Hz alpha band oscillatory power in SPL and FEF with respect to the target speed.
Fast (absolute speed greater than 5 cm/s, pink) and slow (absolute speed lower than 5 cm/s, green) speeds are shown in the VS task (A) averaged over all epochs and (B) averaged over correctly answered epochs. The y-axis represents the z-score of oscillatory power. The x-axis represents time in milliseconds relative to motion onset (0 ms). The blue line shows the 10 Hz power in the Exp Only condition with 2SD error shown in blue shade around the time course. The red line shows the 10 Hz power in the VS condition with 2SD error in red shade around the time course. The black horizontal line indicates z = 0, which is the average normalized baseline power. Dotted lines indicate z = 2 and z = −2 lines.