Dissociated Neural Mechanisms for Face Detection and Configural Encoding: Evidence from N170 and Induced Gamma-Band Oscillation Effects

Abstract

Despite ample research, the structure and the functional characteristics of neural systems involved in human face processing are still a matter of active debate. Here we dissociated between a neural mechanism manifested by the face-sensitive N170 event-related potential effect and a mechanism manifested by induced electroencephalographic oscillations in the gamma band, which have been previously associated with the integration of individually coded features and activation of corresponding neural representations. The amplitude of the N170 was larger in the absence of the face contour but not affected by the configuration of inner components (ICs). Its latency was delayed by scrambling the configuration of the components as well as by the absence of the face contour. Unlike the N170, the amplitude of the induced gamma activity was sensitive to the configuration of ICs but insensitive to their presence within or outside a face contour. This pattern suggests a dual mechanism for early face processing, each utilizing different visual cues, which might indicate their respective roles in face processing. The N170 seems to be associated primarily with the detection and categorization of faces, whereas the gamma oscillations may be involved in the activation of their mental representation.

Absence of Face-specific Cortical Activity in the Complete Absence of Awareness: Converging Evidence from Functional Magnetic Resonance Imaging and Event-related Potentials

“…Although recognition of face identity was not requested in our task, it is likely that, at least on many trials, participants did in fact recognise the famous faces they were shown. If that were the case, N1 could reflect perceptual evidence of face presentation in ventral face-specific areas during a first processing step-previously termed as structural encoding (Zion-Golumbic & Bentin, 2007;Bentin & Deouell, 2000)-whereas N2 could signal access to a specific face representation in a second step (Bentin & Deouell, 2000). A similar idea has been recently proposed by Nasr and Esteky (2009).…”

Selective attention modulates high-frequency activity in the face-processing network

“…Directed attention reliably increases GBA and concomitantly decreases lower frequencies in the alpha (8e12 Hz) and beta (13e30 Hz) band (Fries, Reynolds, Rorie, & Desimone, 2001;Jensen, Kaiser, & Lachaux, 2007;Ossand on et al, 2012;Siegel, Donner, Oostenveld, Fries, & Engel, 2008). GBA has been related to the perception (Rodriguez et al, 1999) and structural encoding of faces (Gao et al, 2013;Zion-Golumbic & Bentin, 2007). Furthermore, processing emotional compared to neutral facial expressions elicited power changes in the delta (.5e4 Hz), theta (4e8 Hz), and gamma band (Balconi & Lucchiari, 2006;Balconi & Pozzoli, 2007).…”

The Cognitive and Neural Basis of Developmental Prosopagnosia

“…Previous studies have shown that N170 components triggered by scrambled faces tend to be enhanced and delayed relative to the N170 in response to intact faces (e.g. Bentin et al, 1996;Zion-Golumbic & Bentin, 2007; for similar N170 modulations caused by other disruptions of the canonical facial configuration, see Letourneau & Mitchell, 2008;Jacques & Rossion, 2010). The fact that face inversion and the spatial scrambling of facial features have similar effects on the N170 emphasize the sensitivity of this N170 component to deviations from a canonical upright face templates, and suggests that these two manipulations may affect the same stages of configural face processing.…”