Recent evidence suggests that visuospatial transformation processes that are known to rely on dorsal stream visual areas (e.g., mental rotation) are temporarily suppressed during saccade execution, but that other aspects of higher-level visual cognition such as object recognition are relatively unaffected by such eye movements (Irwin & Brockmole, 2000, 2004). Here we examined whether this saccadic suppression generalizes to another visuospatial transformation process, namely, misoriented object recognition. Using fMRI, we recently demonstrated that misoriented object recognition and mental rotation result in distinct viewpoint-dependent brain activity, and that misoriented object recognition is not mediated by dorsal stream visual areas (Wilson & Farah, 2006). We therefore hypothesized that saccadic suppression would occur only for parietally-based visuospatial transformation processes, such as mental rotation, and not for temporally-based visuospatial transformation processes, such as misoriented object recognition. Participants viewed line drawings of common objects that were rotated in the picture plane and either named the object (misoriented object recognition) or judged the direction in which the object was facing (mental rotation). In alternating blocks of trials, participants made these decisions while executing saccades of different length. Saccade distance had distinct effects on response times and eye movements (monitored with a corneal-reflectance eye tracking system) in the object recognition and mental rotation conditions. The current results, along with our previous neuroimaging data, provide converging evidence that misoriented object recognition does not involve parietally-based normalization processes such as mental rotation, but rather relies on viewpoint-dependent mechanisms within the inferior temporal lobe.


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