Two kinds of visual perspective taking.

Visual perspective taking can be used to determine where objects are located relative toanother agent, or whether the agent can see a particular object. Four experiments indicated that different processes provide these different kinds of information. When participants were asked to report whether an object was to the left or to the right of another agent, response times (RTs) increased with increasing angular distance between the participant and the agent, suggesting that participants mentally transformed their perspective to align it with that of the agent.

Transformations of visuospatial images.

Transformations of visuospatial mental images are important for action, navigation, and reasoning. They depend on representations in multiple spatial reference frames, implemented in the posterior parietal cortex and other brain regions. The multiple systems framework proposes that different transformations can be distinguished in terms of which spatial reference frame is updated.

Lateral somatotopic organization during imagined and prepared movements.

Motor imagery is a complex cognitive operation that requires memory retrieval, spatial attention, and possibly computations that are analogs of the physical movements being imagined. Likewise, motor preparation may or may not involve computations that are analogs of actual movements. To test whether motor imagery or motor preparation activate representations that are specific to the body part whose movement is imagined or prepared, participants performed, imagined, and prepared hand movements while undergoing functional MRI scanning.

Functional reorganization of spatial transformations after a parietal lesion.

Background: Mental spatial transformations are ubiquitous and necessary for everyday spatial cognition, such as packing luggage into a car or repairing a broken vase. The posterior parietal cortex is known to be involved in performing such transformations.

Objective: To measure reorganization after lesioning of posterior parietal cortex areas subserving spatial transformation.

Imagined viewer and object rotations dissociated with event-related FMRI.

Human spatial reasoning may depend in part on two dissociable types of mental image transformations: object-based transformations, in which an object is imagined to move in space relative to the viewer and the environment, and perspective transformations, in which the viewer imagines the scene from a different vantage point. This study measured local brain activity with event-related fMRI while participants were instructed to either imagine an array of objects rotating (an object-based transformation) or imagine themselves rotating around the array (a perspective transformation). Object-based transformations led to selective increases in right parietal cortex and decreases in left parietal cortex, whereas perspective transformations led to selective increases in left temporal cortex.

Neural correlates of incongruous visual information. An event-related fMRI study.

Incongruous information is better remembered than ordinary information. This result has been attributed both to semantic incongruity and surprise. To determine the contribution of each factor, we performed a functional magnetic resonance imaging study in which participants viewed pictures depicting ordinary and incongruous objects (e.

What is primed in priming from imagery?

Priming from imagery is typically weaker than that from perception. This has been interpreted as resulting from weaker activation of perceptual processes. However, for imagery and perception, commonality is only half the story: Each is also characterized by specific processes.

Less impairment in face imagery than face perception in early prosopagnosia.

There have been a number of reports of preserved face imagery in prosopagnosia. We put this issue to experimental test by comparing the performance of MJH, a 34-year-old prosopagnosic since the age of 5, to controls on tasks where the participants had to judge faces of current celebrities, either in terms of overall similarity (Of Bette Midler, Hillary Clinton, and Diane Sawyer, whose face looks least like the other two?) or on individual features (Is Ronald Reagan's nose pointy?). For each task, a performance measure reflecting the degree of agreement of each participant with the average of the others (not including MJH) was calculated.