Faculty Bibliography

Previous research has shown that imagined perspective rotations elicit spatial and low-level cortical motor areas of the brain when participants rely on knowledge of their physical body, or body percept (Wraga, Flynn, Boyle, & Evans, 2010). The current study used functional magnetic resonance imaging (fMRI) to investigate whether recruitment of the body percept would activate low-level cortical motor areas of the brain within other classes of mental transformations. Participants performed imagined object and perspective rotations of three-dimensional Shephard-Metzler (1971) stimuli. For each task, participants used button presses serving as virtual pointers to locate a prescribed portion of the stimuli with respect to their "right" and "left." We found low-level cortical motor activation (M1) for both mental transformations; however, the degree to which such activation related to participants' performance differed, as well as the recruitment of additional nonmotoric strategies. The results are discussed in terms of recent hypotheses regarding the role of the body percept in extrinsically encoded mental transformations.

Previous behavioral studies suggest that response measures related to the body, such as pointing, serve to anchor participants to their physical body during mental rotation tasks in which their perspective must be shifted elsewhere. This study investigated whether such measures engage spatial and low-level cortical motor areas of the brain more readily than non-body-related measures. We directly compared activation found in two imagined perspective rotation tasks, using responses that varied in the degree to which they emphasized the human body. In the body minimize condition, participants imagined rotating themselves around an object and judged whether a prescribed part of the object would be visible from the imagined viewpoint. In the body maximize condition, participants imagined rotating around the object and then located the prescribed object part with respect to their bodies. A direct comparison of neural activation in both conditions revealed distinct yet overlapping neural regions. The body maximize condition yielded activation in low-level cortical motor areas such as premotor cortex and primary motor cortex, as well as bilateral spatial processing areas. The body minimize condition yielded activation in nonmotoric egocentric processing regions. However, both conditions showed activation in the parietal-occipital region that is thought to be involved in egocentric transformations. These findings are discussed in the context of recent hypotheses regarding the role of the body percept in imagined egocentric transformations.

Mental rotation of objects improves when passive tactile information for the rotating object accompanies the imagined rotation (Wraga, Creem, & Proffitt, 2000). We examined this phenomenon further using a within-subjects paradigm involving handheld objects. In Experiment 1, participants imagined rotating an unseen object placed on their upturned palms. The participants were faster at mental rotation when the object was rotated on their palm than when the object remained stationary. Experiment 2 tested whether the performance advantage would endure when the participants received tactile information for only the start- and endpoints of the rotation event. This manipulation did not improve performance, relative to a stationary control. Experiment 3 revealed that ambiguous tactile information, continuous with the rotation event but independent of object shape, actually degraded performance, relative to a stationary control. In Experiment 4, we found that continuous tactile rotation discrepant from imagined object movement also hindered performance, as compared with continuous tactile information aligned with imagined object movement. The findings suggest a tight coupling between tactile information specifying continuous object rotation and the corresponding internal representation of the rotating object.