The role of the occipital face area in holistic processing involved in face detection and discrimination: A tDCS study.

Abstract

Our results suggest that OFA is causally implicated in facial detection at least in degraded conditions (i.e., when the "face" signal needs to be extracted from a noisy background). In turn, our data do not implicate OFA in holistic processing in face discrimination. Finally, our data suggest a possible role of OFA in categorization of other nonface stimuli, a conclusion that must be taken with caution, as stimulation over OFA may affect object-selective adjacent regions.

The Causal Role of the Occipital Face Area (OFA) and Lateral Occipital (LO) Cortex in Symmetry Perception

“…Figure 1 shows the rightOFA and rightLO sites in one representative partic- ipant. These coordinates are consistent with prior studies (Pitcher et al, 2009(Pitcher et al, , 2012Schwarzkopf et al, 2010;Nagy et al, 2012).…”

“…These stimulation parameters were taken from our previous study (Bona et al, 2014) in which we assessed the involvement of LO in detecting symmetry with the same stimuli as used here in Experiment 1a. Vertex was defined as the midway point between the inion and the nasion and equidistant from left and right intertragal (Pitcher et al, 2007), and has been widely used as a control site in TMS studies as it controls for nonspecific somatosensory effects of TMS without eliciting unintentional neural effects on task performance (Azañó n et al, 2010;Dilks et al, 2013;Ganaden et al, 2013). Here, vertex was used as the baseline against which the effects of OFA and LO TMS were compared.…”

“…We chose not to include any active stimulation sites in the left hemisphere as we were primarily interested in the role of the rightOFA and rightLO. The same stimulation sites were used in the study by Pitcher et al (2007).…”

“…These studies have implicated various extrastriate visual areas, in particular the lateral occipital region (Sasaki et al, 2005;Tyler et al, 2005), and the functional significance of the lateral occipital (LO) cortex in symmetry detection with such stimuli has been demonstrated by recent transcranial magnetic stimulation (TMS) studies Bona et al, 2014). In contrast, the detection of facial symmetry appears to involve the occipital face area (OFA) (Chen et al, 2007), a region in the lateral inferior occipital gyrus and a key node in face processing (Haxby et al, 2000;Rossion et al, 2003;Kadosh et al, 2011;Pitcher et al, 2011;for review, see Atkinson and Adolphs, 2011). Interestingly, the rightOFA shows differential activation between faces and asymmetric scrambled images but not between faces and symmetric scrambled images whereas the fusiform face area (FFA) does so for both contrasts (Chen et al, 2007).…”

“…RightLO was included as a stimulation site because of its established sensitivity to symmetry in such stimuli (Sasaki et al, 2005;Tyler et al, 2005;Bona et al, 2014). The left hemisphere homolog of OFA (leftOFA) was used as a control site, as done in a previous TMS study (Pitcher et al, 2007), because this region is functionally less significant for face perception than the rightOFA. Specifically, lesion studies indicate that the integrity of leftOFA is not necessary for the encoding of facial identity (Landis et al, 1988;Wada and Yamamoto, 2001;Uttner et al, 2002), and TMS evidence indicates that it is not causally involved in discrimination of face parts (Pitcher et al, 2007).…”