The Visual N1 Is Sensitive to Deviations from Natural Texture Appearance

Abstract

Disruptions of natural texture appearance are known to negatively impact performance in texture discrimination tasks, for example, such that contrast-negated textures, synthetic textures, and textures depicting abstract art are processed less efficiently than natural textures. Presently, we examined how visual ERP responses (the P1 and the N1 in particular) were affected by violations of natural texture appearance. We presented participants with images depicting either natural textures or synthetic textures made from the original stimuli. Both stimulus types were additionally rendered either in positive or negative contrast. These appearance manipulations (negation and texture synthesis) preserve a range of low-level features, but also disrupt higher-order aspects of texture appearance. We recorded continuous EEG while participants completed a same/different image discrimination task using these images and measured both the P1 and N1 components over occipital recording sites. While the P1 exhibited no sensitivity to either contrast polarity or real/synthetic appearance, the N1 was sensitive to both deviations from natural appearance. Polarity reversal and synthetic appearance affected the N1 latency differently, however, suggesting a differential impact on processing. Our results suggest that stages of visual processing indexed by the P1 and N1 are sensitive to high-order statistical regularities in natural textures and also suggest that distinct violations of natural appearance impact neural responses differently.

Fig 1. An example of a single original texture (upper left) and its synthetic counterpart (upper right), the original texture with contrast polarity reversed (lower left) and the result of applying both transformations (lower right).

Fig 2. A schematic view of a single trial in our ERP task: Participants viewed sequentially presented texture patches that were either identical, or were different patches drawn from the same larger image.

Contrast polarity and real/synthetic appearance were matched for the two images presented in a single trial and otherwise randomized across the session.

Fig 3. Average values for d’ and c across participants for all conditions in our experiment.

Fig 4. A plot displaying the ERP responses recorded in each condition across the entire scalp.

Each box represents a single channel (with the exclusion of electrodes placed on the cheeks to measure eye movements and the vertex electrode) and is bounded vertically at-5μv and 5μv, horizontally at-100ms and 900ms.

Fig 5. A topographic heat map of the entire scalp for both the P1 and N1 in all stimulus conditions.

Warm colors signify more positive values, cool colors signify more negative values.

Fig 6. Grand average ERP waveforms for all stimulus conditions at left, midline and right occipital sites.

While the P1 does not appear to be sensitive to either contrast negation or real/synthetic appearance, the N1 is sensitive to both.