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Cibu Thomas, Galia Avidan, Kwan-jin Jung, Marlene Behrmann; Disruption in structural connectivity in ventral cortex in congenital prosopagnosia. Journal of Vision 2006;6(6):88. doi: 10.1167/6.6.88.
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Congenital prosopagnosia (CP) refers to the lifelong deficit in face processing in the absence of an obvious neural deficit and in the presence of intact sensory and intellectual function. Surprisingly, imaging studies have revealed that CP individuals show normal activation in the fusiform face area (FFA) with differences from controls emerging in more anterior cortical regions, suggesting normal FFA function and a possible disruption of neural connectivity from FFA to other regions. To test this hypothesis, we examined the structural integrity of several major fiber tracts using diffusion tensor imaging (DTI) in 5 CP and 10 normal control subjects. Fiber tracking was performed using DTI studio (Mori, et al., 2002), with FA threshold of 0.20 and critical angle of 40. The fasciculi of interest (FOI) included the inferior fronto-occipital fasciculus (IFOF), the inferior longitudinal fasciculus, the forceps major and the forceps minor. The dependent measures included mean FA values within a FOI, the number of voxels that indicate the presence of a fiber, and a connectivity score derived by documenting whether the fibers in a particular FOI terminate at a predefined cortical region. The data indicate that, in contrast with the control group, there is a disruption of structural connectivity to more anterior cortical regions in the CP group. These findings provide a better understanding of the neural substrate giving rise to CP and help elucidate the role of the FFA and other cortical regions involved in normal face recognition.
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