Spatio-Temporal Brain Mapping of Motion-Onset VEPs Combined with fMRI and Retinotopic Maps

Neuroimaging studies have identified several motion-sensitive visual areas in the human brain, but the time course of their activation cannot be measured with these techniques. In the present study, we combined electrophysiological and neuroimaging methods (including retinotopic brain mapping) to determine the spatio-temporal profile of motion-onset visual evoked potentials for slow and fast motion stimuli and to localize its neural generators. We found that cortical activity initiates in the primary visual area (V1) for slow stimuli, peaking 100 ms after the onset of motion. Subsequently, activity in the mid-temporal motion-sensitive areas, MT+, peaked at 120 ms, followed by peaks in activity in the more dorsal area, V3A, at 160 ms and the lateral occipital complex at 180 ms. Approximately 250 ms after stimulus onset, activity fast motion stimuli was predominant in area V6 along the parieto-occipital sulcus. Finally, at 350 ms (100 ms after the motion offset) brain activity was visible again in area V1. For fast motion stimuli, the spatio-temporal brain pattern was similar, except that the first activity was detected at 70 ms in area MT+. Comparing functional magnetic resonance data for slow vs. fast motion, we found signs of slow-fast motion stimulus topography along the posterior brain in at least three cortical regions (MT+, V3A and LOR)

Talairach coordinates of the significant activations in the averaged fMRI data from thirteen subjects.

<p>Coordinates are given for contralateral activations in response to stimuli in each of the four conditions (values are in mm).</p

Group fMRI activations for slow and fast motion stimuli rendered on the semi-inflated cortical surface reconstruction of the left hemisphere of the average brain (left section).

<p>Results are also shown in a close-up view of the posterior part of the brain rendered on a flat map. Results from upper and lower hemifields are collapsed together. Activations for slow and fast motion conditions are plotted in different colors to represent their topographic specificity. Labels and insets are the same as those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035771#pone-0035771-g003" target="_blank">Figure 3</a>.</p

Coregistration of the VEP/fMRI responses to slow motion stimuli.

<p>a) Group-averaged contralateral fMRI activations superimposed on the flattened hemisphere (occipital lobe) of the PALS template. The pseudocolor scale indicates the statistical significance of the fMRI activations. Major sulci (dark gray) are labeled as follows: parieto-occipital sulcus (POS), intraparietal sulcus (IPS), posterior intraparietal sulcus (pIPS), superior temporal sulcus (STS), middle temporal sulcus (MTS), inferior temporal sulcus (ITS), lateral occipital region (LOR), fusiform gyrus (fusiform) and calcarine fissure (Calcarine). The dashed outline surrounding area MT+ represents the group-averaged location of the motion-sensitive cortex based on separate localizer scans. b) Schematic representation of the source locations in the unseeded dipole model. c) Source waveforms of the dipoles seeded to the fMRI activations.</p

Talairach coordinates of the unseeded source models based on VEP data only.

<p>Coordinates are given for contralateral activity in response to stimuli in each of the four conditions (values are in mm).</p

Coregistration of the VEP/fMRI responses to fast motion stimuli.

<p>For other detail, see the caption for <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035771#pone-0035771-g003" target="_blank">Figure 3</a>.</p

Benefits of Sports Participation for Executive Function in Disabled Athletes

We investigated the effect of sports activity on physically-disabled individuals using behavioral and electrophysiological techniques. Visual go/no-go discriminative and simple response tasks were used. Participants included 17 disabled athletes, 9 from open-skill (wheelchair basketball) and eight from closed-skill (swimming) sports, and 18 healthy non-athletes. Reaction times of the disabled athletes were slower than those of healthy non-athletes on both tasks (7% and 13% difference, respectively). Intra-individual variations in reaction times, switch cost, and number of false alarms, were higher in the swimmers, but comparable to healthy non-athletes, in the basketball group. Event-related potentials (ERPs) early components P1, N1, and P2 had longer latencies in the disabled athletes. The late P3 component had longer latency and smaller amplitude in the disabled athletes only in the discriminative response task. The N2 component, which reflected inhibition/execution processing in the discriminative response task, was delayed and reduced in the swimmer group, but was comparable to healthy subjects in the basketball group. Our results show that (1) the ERP components related to perceptual processing, and late components related to executive processing, were impaired in disabled subjects; and (2) open-skill sports such as basketball may partially compensate for executive control impairment by fostering the stability of motor responses and favoring response flexibility

Mean MNI coordinates of ROIs identified in the present study.

<p>In the case of V6, MT+, CSv, V3A and IPSmot regions, ROIs were extracted from the statistical contrast (M-S). In the case of V6 (localizer), MT (localizer), and MST+ (localizer), ROIs were extracted from their functional localizers. The table shows the coordinates of the maxima of the motion activated regions (values are in mm). All maxima were significant at p<0.05 (whole brain, FDR corrected).</p

Cortical responses to motion coherency.

<p>Average motion coherence coefficients extracted from the functionally defined ROIs (see Materials and Methods). (A) MC/MI coefficient in areas CSv, V3A, and IPSmot, as defined by the group statistical contrast (M-S) and in areas V6, MT and MST+, as defined by functional localizer. (B) MC/MI coefficient in area V6, as defined by the group statistical contrast (M-S) and by functional localizer. (C) MC/MI coefficient in area MT+, as defined by the statistical contrast (M-S) and in its functional subdivisions MT and MST+, as defined by functional localizer. The MC/MI coefficient of 1 is marked by a thicker orange horizontal line to indicate identical response to both kinds of motion. Bars represent the mean coefficients ± standard error of the mean across runs and participants (n indicates number of hemispheres).</p

Schematic representation of the stimuli we used in the main fMRI experiment (ff-3D).

<p>Schematic representation of the stimuli we used in the main fMRI experiment (ff-3D).</p