Time course of spatial frequency integration in face perception: An ERP study.

Face perception is based on the processing and integration of multiple spatial frequency (SF) ranges. However, the temporal dynamics of SF integration to form an early face representation in the human brain is still a matter of debate. To address this issue, we recorded event-related potentials (ERPs) during the presentation of spatial frequency-manipulated facial images. Twenty-six participants performed a gender discrimination task on non-filtered, low-, high-, and band-pass filtered face images, corresponding, respectively, to the full range, spatial frequencies up to 8 cycles/image, above 32 cycles/image, and from 8 to 16 cycles/image. Behaviorally, the task related-performance was more accurate and faster for non-filtered (NF) and mid-range SF (MSF) than for low SF (LSF) and high SF (HSF) stimuli. At both behavioral and electrophysiological levels, response to MSF contained in faces did not differ from the responses to full spectrum non-filtered (NF) facial images. In ERPs, LSF facial images evoked the largest P1 amplitude while HSF facial images evoked the largest N170 amplitude compared with the other three conditions. Since LSFs and HSFs would transmit global and local information respectively, our observations lend further support to the "coarse-to-fine" processing theory of faces. Furthermore, they offer original evidence of the effectiveness and adequacy of the mid-range spatial frequency in face perception. Possible theoretical interpretations of our findings are discussed.

Factors influencing spatial frequency extraction in faces: A review.

JEANTET, C., Caharel, S., Schwan, R., Lighezzolo-Alnot, J., and Laprevote, V. Factors influencing spatial frequencies extraction in faces: a review. NEUROSCI BIOBEHAV REV XX(X) XXX-XXX, 2017. Spatial frequency is an elementary aspect of visual perception. Moreover, faces elicit distinct responses by the human visual system when compared to other visual objects. This review examines the factors influencing spatial frequency processing in faces. Visual perception of a face results from the interaction between the physical properties of the stimulus and the human visual system. We first review the methodology of visual stimulus production and presentation in the assessment of spatial frequency processing in faces. Image properties interact with the physical constraints of the visual system. Other cognitive phenomena also drive the processing of spatial frequencies in faces. Finally, the observer's characteristics may further influence this spatial processing. Overall, the studies indicate that spatial frequency processing in faces is not a fixed process, conditioned by physical constraints alone, but a flexible process, dependent of various cognitive constraints, developmental, and health conditions. Finally, limitations and new challenges are discussed.