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Tim C Kietzmann, Sam Ling, Sonia Poltoratski, Peter König, Randolph Blake, Frank Tong; The Occipital Face Area is Causally Involved in Viewpoint Symmetry Judgments of Faces. Journal of Vision 2014;14(10):125. doi: https://doi.org/10.1167/14.10.125.
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© ARVO (1962-2015); The Authors (2016-present)
Humans are highly proficient at recognizing individual faces from a wide variety of viewpoints, but the neural substrates underlying this ability remain unclear. Recent work suggests that viewpoint-symmetric responses to rotated faces, found across a large network of visual areas, may constitute a key computational step in achieving full viewpoint invariance. Here, we used transcranial magnetic stimulation (TMS) to examine whether the occipital face area (OFA) causally contributes to the perception of viewpoint symmetry. The experiment followed a 2x2 design with TMS (repetitive vs. sham) and task (symmetry vs. angle judgments) as experimental factors. Subjects underwent 5 minutes of either sham stimulation or true 1Hz rTMS to the right OFA prior to each 4-minute block of behavioral test trials. Visual stimuli were presented ipsilateral to the site of TMS stimulation to avoid retinotopically specific impairments. Subjects reported either which of two consecutively presented pairs of face viewpoints was mirror-symmetric (symmetry task) or which pair of faces had a larger angular difference (angle task). Prior to the experiment, both tasks were titrated by an adaptive staircase procedure (QUEST) to achieve an average of 80% correct performance. Compared to sham, rTMS led to a significant decrease in performance specifically for viewpoint symmetry judgments, whereas no significant differences were found for the angle task. A repeated-measures ANOVA revealed a significant interaction effect, indicating that the effect of rTMS over OFA was larger for symmetry than for angle judgments. Our data provide novel evidence for the causal involvement of OFA in the processing of viewpoint symmetry and provide important restrictions on models of viewpoint symmetry and face perception in general. In particular, the specific effect on viewpoint symmetry judgments after rTMS applied to the ipsilateral OFA provides support for proposals emphasizing the role of inter-hemispheric sharing of information in the perception of viewpoint symmetry.
Meeting abstract presented at VSS 2014
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