An event-related potential study of contextual modifications in a face recognition task

Abstract

Event-related potentials (ERP) were recorded during a task involving the short-term recognition of unfamiliar faces. The purpose was to study the effects of changing the intrinsic context (facial expression) and/or the extrinsic context (background) between the encoding and recognition of a face. The new face caused an increase in the parietal N170 amplitude, but this component was not affected by contextual modifications. In contrast, the frontal N200 was very sensitive to context changes. There was also a well-defined, late parietal component modulated by the processing of information relevant to the face recognition decision. This late positive component reached its amplitude peak when the decision criterion was the strictest. The results obtain showed that ERP can be modulated by these context variations even though they are irrelevant to the task at hand.

Electrophysiological study of contextual variations in a short-term face recognition task

“…The influence of the processing context (interactive vs. independent) seems to be manifested on both the early components (e.g., N170, N250) and the parietal repetition effect, particularly in the left hemisphere. However, the magnitude of the parietal repetition effect observed here is large relative to the right parietal repetition effect observed in an earlier study using a short-term unfamiliar face recognition task, in which contextual information was unnecessary [30]. Did the ERP repetition effect that showed up on the left parietal component also occur when the recognition involved contextual elements that are irrelevant to the task at hand?…”

“…200-500 ms. FN250 and the early part of the parietal repetition effect were analyzed within the 200-500 ms temporal window. Regions of interest were selected a priori based on previous results, suggesting that early frontal negativities are maximal over frontal regions [6,30,45,55], whereas parietal repetition effects are maximal over posterior regions [5,24,57,62]. This distinction between anterior and posterior components was also confirmed by visual inspection of the average waveforms (see Figs.…”

“…Moreover, it has become clear that these components are affected by contextual information. For example, contextual variations, even if they are irrelevant to the task at hand (contextindependent), affect this component during the short-term recognition of unfamiliar faces [30].…”

Semantic Learning Modifies Perceptual Face Processing

“…ERPs were recorded before and after learning, and we were interested in learning-induced changes in the N170, an ERP component primarily implicated in perceptual face processing (Carmel & Bentin, 2002;Sagiv & Bentin, 2001;Eimer, 2000b;Bentin et al, 1996). We expected a change in the N170 repetition effect, which is characterized by a reduction in the N170 amplitude following immediate presentations of the same face (Heisz et al, 2006a(Heisz et al, , 2006bItier & Taylor, 2002, 2004Guillaume & Tiberghien, 2001;Campanella et al, 2000;George, Evans, et al, 1997;George, Jemel, et al, 1997). The N170 repetition effect is observed for unfamiliar faces but not familiar faces (Henson et al, 2003;Caharel et al, 2002;Schweinberger, Pickering, Jentzsch, et al, 2002), therefore we expected the repetition effect to be reduced or eliminated following face learning.…”

“…Characterized by a reduction in the N170 amplitude following immediate face presentations (Heisz, Watter, & Shedden, 2006a, 2006bItier & Taylor, 2002, 2004Guillaume & Tiberghien, 2001;Campanella et al, 2000;George, Jemel, Fiori, & Renault, 1997), the N170 repetition effect is observed for repeated presentation of the same image (Heisz et al, 2006a(Heisz et al, , 2006bItier & Taylor, 2002, 2004George, Jemel, et al, 1997), as well as successive presentation of two images portraying the same individual with different facial expressions (Guillaume & Tiberghien, 2001), different background images (Guillaume & Tiberghien, 2001), or completely different physical images (Campanella et al, 2000), suggesting that the effect cannot be explained as perceptual habituation. Importantly, N170 repetition effects are only observed for unfamiliar faces.…”