Abstract
Functional Magnetic Resonance Imaging (fMRI) studies investigating human face perception use localizers to identify specific brain areas, such as the fusiform face area (FFA), occipital face area (OFA), and superior temporal sulcus (STS). These usually consist of a simple block design contrasting viewing of static pictures of faces and viewing of other objects. Functional localizers seldom identify all regions in all participants, however, reducing their utility in the study of single subjects. We asked whether the use of more ecologically valid dynamic stimuli, such as video clips of faces and objects, may result in a more reliable activation of face-processing areas in all participants. Sixteen young volunteers participated in an fMRI study that contained two functional localizers, one with static photographs and the other with dynamic video clips of faces and objects. The results showed that the use of the static localizer resulted in the identification of the FFA bilaterally in 13 participants, the left OFA in 11, the right STS and right OFA in eight, and the left STS in four. The use of the dynamic localizer allowed us to detect activity within the FFA bilaterally, the right STS and the right OFA in all 16 participants, and the left STS and left OFA in 13. Furthermore, face-selective regions identified with the dynamic localizer had peaks with 25% greater t-values and had, on average, twice many voxels than the regions identified with the static localizer. These findings suggest that the use of more realistic dynamic stimuli, rather than static photographs, results in a more reliable localization of the brain regions involved in face perception.
This work was supported by operating grants from the CIHR (MOP-77615) and NIMH (R01 MH069898). CJF was supported by a CIHR Graduate Scholarship Doctoral Research Award and a MSFHR Senior Graduate Studentship. GI was supported by the Alzheimer Society of Canada and the MSFHR. JJSB was supported by a Canada Research Chair and a Senior Scholarship from the MSFHR.