RT Journal Article
SR Electronic
T1 Face Selective Neural Activity: comparison between fixed and free viewing
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 748756
DO 10.1101/748756
A1 Carmel R. Auerbach-Asch
A1 Oded Bein
A1 Leon Y. Deouell
YR 2019
UL http://biorxiv.org/content/early/2019/08/28/748756.abstract
AB Event Related paradigms (ERPs) are widely used to study category-selective EEG responses to visual stimuli, such as the face-selective N170 component. While allowing for good experimental control these paradigms ignore the dynamic role of eye-movements in natural vision. Fixation-related potentials (FRPs) obtained using simultaneous EEG and eye-tracking overcome this limitation. While various studies have used FRPs to study processes such as lexical processing, target detection and attention allocation, no study has directly examined categorical visual recognition in free-viewing conditions. The goal of this study was to compare the well-known face-sensitive activity evoked by stimulus abrupt appearance (N170 component) with that evoked by self-controlled fixations on a stimulus. Twelve subjects were studied in three experimental conditions: Free-viewing (FRPs), Cued-viewing(FRPs) and Control (ERPs). We used a multiple regression GLM approach to disentangle overlapping components. Our results show that the N170 face differential effect (face vs. non-face) is evident for the first fixation on a stimulus, whether it follows a self-generated saccade or stimulus appearance at fixation point. Whereas the N170 differential effect has similar topography across viewing conditions, there are major differences between ERP and FRP activity within each stimulus category. We hypothesized that the fixation-related Lambda complex may overlap the N170 in FRPs, and establish the plausibility of this account using hypothesis-driven dipole simulations. This study establishes the use of the N170 effect as a signature of face detection in free viewing experiments while highlighting the importance of accounting for fixation-specific effects.