The effects of visual imagery on face identification: an ERP study

Abstract

The present study tested the hypothesis that the effects of mental imagery on subsequent perception occur at a later matching stage in perceptual identification, but not in the early perceptual stage as in perceptual detection. The behavioral results suggested that the effect of visual imagery on visual identification is content-specific, i.e., imagining a congruent face facilitates face identification, whereas a mismatch between imagery and perception leads to an interference effect. More importantly, the ERP results revealed that a more negative N2 response to the subsequent visual face stimuli was elicited over fronto-central sites in the mismatch and no-imagery conditions as compared to that in the match condition, with the early P1 and N170 components independent of manipulations. The latency and distribution of the neural effects demonstrate that the matching step, but not the earlier perceptual process, is affected by the preceding visual imagery in the context of face identification. We discuss these results in a broader context that the imagery-perception interaction may depend on task demand.

Keywords: N170; N2; event-related potentials; face identification; matching; visual imagery.

Figure 1

Schematic description of the experimental paradigm. After the presentation of fixation, one of these three letter sounds was presented and participants were asked to imagine the corresponding face vividly and then press the “Space” bar in the self-paced interval. For the no imagery associated sound, participants were asked to simply press “Space” once hearing the letter. After a random delay between 800 and 1200 ms, one of these two real faces was presented for 200 ms and participants were asked to press one of the two buttons according to which of the two faces presented on the screen. After the response a visual noise mask with duration of 200 ms was presented before the next trial began.

Figure 2

The mean reaction times in the face identification task. Error bars represent two standard errors of the mean (SEM). ^**p < 0.01; ^***p < 0.001.

Figure 3

Grand averaged ERPs illustrating the P1 and the N170 elicited by visual stimuli in three conditions.

Figure 4

The left panel illustrates the grand averaged ERPs in mismatch and match conditions and their difference wave. The right panel illustrates the grand averaged ERPs in no imagery and match conditions and their difference wave. The gray areas highlight the time windows of N2 (250–350 ms) used for statistical analysis. The scalp distributions are time-locked to the peak amplitude of the difference wave (Left: Mismatch minus Match; Right: No imagery minus Match).