The neural correlates of illusory face perception: An fMRI study

Individuals often report seeing a face in the clouds, their toast, or a tortilla. These informal observations suggest that our visual system is highly tuned to perceive faces, potentially due to the high social importance of faces or face processing expertise. Previous fMRI studies of this top-down bias to perceive faces have mainly examined the neural correlates of imagining faces or perception of ambiguous faces. However, the neural mechanisms underlying the illusory processing of faces are unclear. To address this question, in the present study, participants were instructed to detect faces (face task) and letter (letter task) in pure noise images after training in which increasingly noisy face or letter images were used. The pure noise images actually contained neither faces nor letters. Trials were classified into 4 conditions according to whether participants responded that they had "seen" a face or a letter in a pure noise image: face response, no-face response, letter response, and no-letter response. A repeated two-way ANOVA of task (face vs. letter) by detection (face or letter response vs. no response) was performed on the fMRI activities of each face-preferential area, namely the fusiform face area (FFA) and the occipital face area (OFA). Results revealed that the right FFA showed significantly greater activity for face responses than for no-face responses, whereas it showed equal responses to the letter and no-letter response. Within the left FFA and bilateral OFA, regardless of the face or letter task, the neural activity for detection responses was significantly greater than no-detection responses. Our findings suggest that the right FFA is specifically involved in the illusory processing of faces, whereas the left FFA and the bilateral OFA are involved in the illusory processing of visual objects more generally. Meeting abstract presented at VSS 2012