The effect of parametric stimulus size variation on individual face discrimination indexed by fast periodic visual stimulation

Abstract

BackgroundThe human brain is frequently exposed to individual faces across a wide range of different apparent sizes, often seen simultaneously (e.g., when facing a crowd). Here we used a sensitive and objective fast periodic visual stimulation approach while recording scalp electroencephalogram (EEG) to test the effect of size variation on neural responses reflecting individual face discrimination.MethodsEEG was recorded in ten observers presented with the same face identity at a fixed rate (5.88 Hz, frequency F) and different oddball face identities appearing every five faces (F/5, i.e., 1.18 Hz). Stimulus size was either constant (6.5 × 4 degrees of visual angle) or changed randomly at each stimulation cycle, by 2:1 ratio increasing values from 10% to 80% size variation in four conditions. Absolute stimulus size remained constant across conditions.ResultsThe base rate 5.88 Hz EEG response increased with image size variation, particularly over the right occipito-temporal cortex. In contrast, size variation decreased the oddball response marking individual face discrimination over the right occipito-temporal cortex. At constant stimulus size, the F/5 change of identity generated an early (about 100 ms) oddball response reflecting individual face discrimination based on image-based cues. This early component disappeared with a relatively small size variation (i.e., 20%), leaving a robust high-level index of individual face discrimination.ConclusionsStimulus size variation is an important manipulation to isolate the contribution of high-level visual processes to individual face discrimination. Nevertheless, even for relatively small stimuli, high-level individual face discrimination processes in the right occipito-temporal cortex remain sensitive to stimulus size variation.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2202-15-87) contains supplementary material, which is available to authorized users.

Neural correlates of perceptual color inferences as revealed by #thedress

“…The processing of each image likely persists to some extent until it is interrupted, such that rapid serial visual presentation paradigms have led to behavioral and neural response signatures within less than 20 ms presentation duration (Keysers et al, 2001;Potter et al, 2014). While the display time of each image here is brief, a study by Foster, Craven, and Sale (1992), showed that illuminant vs. surface color changes were detected extremely rapidly, even below 83 ms. At each image presentation, the size varied from 90-110% of the size of the original image in 10% steps to reduce pixel-based image repetition effects (see Dzhelyova & Rossion, 2014). As described in the Introduction, in Experiment 1 there were two experimental conditions, in each of which a pair of images of the dress were presented in alternation: (1) blue-yellow, alternating the original bluish and hue-inverted yellowish images of the dress; and (2) green-red, alternating the greenish and reddish images of the dress.…”

The contribution of color information to rapid face categorization in natural scenes

“…To consider the variations of noise across the amplitude spectrum, a baseline subtraction was applied to each frequency component by subtracting the average amplitude of 20 surrounding frequency components (10 on each side, excluding the immediately adjacent bins and the local minimum and maximum bins; see, for example, Dzhelyova & Rossion, 2014;Mouraux et al, 2011) from the amplitude of the frequency component of interest. In addition, the signal-to-noise ratio (SNR) was also calculated by considering the same 20 surrounding frequency components (e.g., Rossion, Alonso Pireto, Boremanse, Kuefner, & Van Belle, 2012).…”

Immediate stimulus repetition abolishes stimulus expectation and surprise effects in fast periodic visual oddball designs

“…Experiments designed to assess facial identity discrimination with FPVS typically control for repetition of low-level image features by randomly varying size at every presentation cycle (e.g., Liu-Shuang et al, 2014;Dzhelyova & Rossion, 2014a;2014b;Xu et al, 2017). Moreover, in these experiments different and highly variable face identities are introduced at every oddball cycle, rather than the same oddball face identity, preventing repetition effects across oddball changes, increasing the individual face discrimination response, and minimizing again the contribution of low-level visual cues to this individual face discrimination response (Liu-Shuang et al, 2014;Dzhelyova & Rossion, 2014a;2014b;Xu et al, 2017).…”