Differential processing of objects under various viewing conditions in thehuman lateral occipital complex

The invariant properties of human cortical neurons cannot be studied direct ly by fMRI due to its limited spatial resolution. Here, we circumvented thi s limitation by using fMR adaptation, namely, reduction of the fMR signal d ue to repeated presentation of identical images. Object-selective regions ( lateral occipital complex [LOC]) showed a monotonic signal decrease as repe tition frequency increased. The invariant properties of fMR adaptation were studied by presenting the same object in different viewing conditions. LOC exhibited stronger fMR adaptation to changes in size and position (more in variance) compared to illumination and viewpoint. The effect revealed two p utative subdivisions within LOG: caudal-dorsal (LO), which exhibited substa ntial recovery from adaptation under all transformations, and posterior fus iform (PF/LOa), which displayed stronger adaptation. This study demonstrate s the utility of fMR adaptation for revealing functional characteristics of neurons in fMRI studies.