# Visual Demands of Walking Are Reflected in Eye-Blink-Evoked EEG-Activity
## 3 Results
### EEG Parameters  
#### 3.2.1 ERPs  
ERP waveshapes were substantially different between walking conditions but fairly similar across blocks (see Figure 2). Most of the parameters neither revealed a main effect of experimental block nor an interaction between walking conditions and experimental block, with all F-values being around 1 and below. Thus, they will not be mentioned in detail here, again, for the sake of brevity and with all results being given in Appendix A.  
Figure 3: Behavioral data (mean and standard error of mean) obtained in the three walking conditions, separately, for block 1 (red) and block 2 (black). Head acceleration steadily increased with walking complexity. Head dynamics were largest when walking on meadow. When crossing the obstacle course, head dynamics were reduced, possibly due to head stabilization for fixations. Blink intervals increased on the obstacle course; on the other hand, blink duration increased while standing. Significant effects of walking condition are depicted for all pairwise comparisons (**: \(p<0.001\); **: \(p<0.01\)). **The amplitude of the N1 was increased when walking compared to standing (F(1,35) = 14.72, \(p\) = 0.001, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.28), but decreased when traversing the obstacle course was compared to walking on the meadow (F(1,35) = 47.57, \(p\) < 0.001, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.56) (see Figure 4 for the topography of this effect, which is clearly focused in visual areas). For the comparison of meadow vs. obstacle course, an interaction of block by walking condition was found (F(1,35) = 7.24, \(p\) = 0.021, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.15), indicating that the occipital N1 amplitude was highest when participants walked on the meadow for the second time. In contrast to this finding, the fronto-central N2 amplitude decreased from standing to walking (F(1,35) = 14.53, \(p\) = 0.001, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.27), and further from walking the meadow to walking the obstacle course (F(1,35) = 16.77, \(p\) < 0.001, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.30). The parietal P2 slightly increased in amplitude from standing to walking the meadow (F(1,35) = 8.44, \(p\) = 0.012, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.17). The continuation of this effect, visible in Figure 4, from walking the meadow to walking the obstacle course, did not reach significance (F(1,35) = 3.17, \(p\) > 0.1). The occipital P2, however, showed a highly significant decrease in amplitude with increasing complexity of the walking conditions: standing vs. walking the meadow (F(1,35) = 15.28, \(p\) < 0.001, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.28), and walking on meadow vs. walking the obstacle course (F(1,35) = 25.57, \(p\) < 0.001, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.41). Finally, the parietal P3 amplitude showed a linearly decreasing effect of increasing walking complexity. The P3 amplitude was slightly larger for standing compared to walking (F(1,35) = 5.24, \(p\) = 0.056, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.11) and decreased further when participants walked the obstacle course ( F(1,35) = 16.72, \(p\) < 0.001, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.30). For the P3 component, however, significant effects of block were found in both analyses (F(1,35) = 10.28, \(p\) = 0.006, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.20; and F(1,35) = 6.15, \(p\) = 0.036, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.13), with larger amplitudes in the second blocks. In the latter analysis, comparing walking on meadow vs. walking the obstacle course, an additional interaction of walking condition by block was obtained (F(1,35) = 8.87, \(p\) = 0.011, \({}_{\text{adj}}\eta_{\text{p}}{}^{2}\) = 0.18), likely due to the reduction of the block effect on P3 amplitude in the obstacle course condition. Figure 4: Amplitudes of the eye-blink-related EEG potentials (mean and standard error of means) and topographical plot for the comparison of the two walking conditions around the latency of the N1.