Feature-specific electrophysiological correlates of texture segregation

Abstract

Discrimination between a figure and its surround is an important first step of pattern recognition. This discrimination usually relies, as a first step, on the detection of borders between a figure and its surround, for example based on spatial gradients in luminance, colour, or texture. There is evidence that neurones in the visual cortex are specifically activated by segregation between textures, but the relation between segregation based on different types of features such as colour, luminance, and motion is unclear. Evoked EEG potentials specific to texture segregation were investigated in 17 observers in two separate experiments and by means of functional magnetic resonance imaging in a separate study (Fahle et al., in preparation). Differences in either luminance, colour, line orientation, motion, or stereoscopic depth defined a checkerboard pattern. Patterns defined by each of these features elicited segregation-specific potentials. In contrast to earlier reports (Vision Research 37 (1997) 1409), however, we find pronounced differences between the segregation-specific potentials evoked through different features, especially regarding their peak latencies. The topographical distribution of the activity evoked reveals different polarities and partly specific locations for different stimulus features, indicating the existence of different processors for texture segregation based on different features.

Neural representation of feature synergy

“…This contour-specific negative deflection resembles a negative shift observed at occipital electrodes for both single-and double-feature target GRF stimuli in experiments 2 and 3 of the present study, regarding latency, spatial distribution, and experimental conditions where these were elicited. The contourspecific negative deflection also resembles the texture segregation visual-evoked potential (tsVEP), which has been observed at occipital electrodes (Bach and Meigen, 1997;Bach et al, 2000;Casco et al, 2005;Fahle et al, 2003;Romani et al, 2003). In contrast, the longlasting negative deflection we observed was found locally at an inferior temporal electrode when synergy was observed by presenting two features simultaneously.…”

Attentive and pre-attentive aspects of figural processing

“…Previous texture-segmentation VEP studies have reported an enhancement of late activity when the texture segmentation is task relevant (Bach & Meigen, 1992, 1997Caputo & Casco, 1999;Casco et al, 2005;Fahle, Quenzer, Braun, & Spang, 2003;Heinrich et al, 2007;Khoe, Freeman, Woldorff, & Mangun, 2006;Schubo, Schroger, & Meinecke, 2004). In our displays, the dominant amplitude effects occur on the low-frequency interaction terms.…”

The neural origins of visual crowding as revealed by event-related potentials and oscillatory dynamics

“…This result is consistent with the evidence of Chicherov et al (2014) that, though with a different behavioral paradigm, equally demonstrated that the earliest signature of visual crowding was a suppression of the N1 component. Previous studies on texture segmentation (Bach & Meigen, 1992Caputo & Casco, 1999;Fahle, Quenzer, Braun, & Spang, 2003) and contour detection Mathes, Trenner, & Fahle, 2006;Shpaner, Molholm, Forde, & Foxe, 2013) typically found N1 suppression to be associated with the inability to segment a stimulus target from the background. Conversely, N1 amplitude is enhanced when a structure emerges (Kanizsa figures, Murray et al, 2002;Glass patterns, Pei, Pettet, Vildavski, & Norcia, 2005).…”