Biomedical subjects

Sarah H Creem-Regehr

Publications and source records attributed to Sarah H Creem-Regehr.

5 recordsLinked to original sources

PubMed2005

The influence of restricted viewing conditions on egocentric distance perception: implications for real and virtual indoor environments.

We carried out three experiments to examine the influence of field of view and binocular viewing restrictions on absolute distance perception in real-world indoor environments. Few of the classical visual cues provide direct information for accurate absolute distance judgments to points in the environment beyond about 2 m from the viewer. Nevertheless, in previous work it has been found that visually directed walking tasks reveal accurate distance estimations in full-cue real-world environments to distances up to 20 m. In contrast, the same tasks in virtual environments produced with head-mounted displays (HMDs) show large compression of distance. Field of view and binocular viewing are common limitations in research with HMDs, and have been rarely studied under full pictorial-cue conditions in the context of distance perception in the real-world. Experiment 1 showed that the view of one's body and feet on the floor was not necessary for accurate distance perception. In experiment 2 we manipulated the horizontal and the vertical field of view along with head rotation and found that a restricted field of view did not affect the accuracy of distance estimations when head movement was allowed. Experiment 3 showed that performance with monocular viewing was equal to that with binocular viewing. These results have implications for the information needed to scale egocentric distance in the real-world and reduce the support for the hypothesis that a limited field of view or imperfections in binocular image presentation are the cause of the underestimation seen with HMDs.

Adult↗

PubMed2004

Neural representations of graspable objects: are tools special?

Recent cognitive and neuroimaging studies have examined the relationship between perception and action in the context of tools. These studies suggest that tools "potentiate" actions even when overt actions are not required in a task. Tools are unique objects because they have a visual structure that affords action and also a specific functional identity. The present studies investigated the extent to which a tool's representation for action is tied to its graspability or its functional use. Functional magnetic resonance imaging (fMRI) was used to examine the motor representations associated with different classes of graspable objects. Participants viewed and imagined grasping images of 3D tools with handles or neutral graspable shapes. During the viewing task, motor-related regions of cortex (posterior middle temporal gyrus, ventral premotor, and posterior parietal) were associated with tools compared to shapes. During the imagined grasping task, a frontal-parietal-temporal network of activation was seen with both types of objects. However, differences were found in the extent and location of premotor and parietal activation, and additional activation in the middle temporal gyrus and fusiform gyrus for tools compared to shapes. We suggest that the functional identity of graspable objects influences the extent of motor representations associated with them. These results have implications for understanding the interactions between "what" and "how" visual processing systems.

Adult↗

PubMed2004

Perceiving virtual geographical slant: action influences perception.

In 4 experiments, the authors varied the extent and nature of participant movement in a virtual environment to examine the influence of action on estimates of geographical slant. Previous studies showed that people consciously overestimate hill slant but can still accurately guide an action toward the hill (D. R. Proffitt, M. Bhalla, R. Gossweiler, & J. Midgett, 1995). Related studies suggest that one's potential to act may influence perception of slant and that distinct representations may independently inform perceptual and motoric responses. The authors found that in all conditions, perceptual judgments were overestimated and motoric adjustments were more accurate. The virtual environment allowed manipulation of the effort required to walk up simulated hills. Walking with the effort appropriate to the visual slant led to increased perceptual overestimation of slant compared with active walking with the effort appropriate to level ground, while visually guided actions remained accurate.

Adolescent↗

PubMed2004

Spatial updating of virtual displays during self- and display rotation.

In four experiments, we examined observers' ability to locate objects in virtual displays while rotating to new perspectives. In Experiment 1, participants updated the locations of previously seen landmarks in a display while rotating themselves to new views (viewer task) or while rotating the display itself (display task). Updating was faster and more accurate in the viewer task than in the display task. In Experiment 2, we compared updating performance during active and passive self-rotation. Participants rotated themselves in a swivel chair (active task) or were rotated in the chair by the experimenter (passive task). A minimal advantage was found for the active task. In the final experiments, we tested similar manipulations with an asymmetrical display. In Experiment 3, updating during the viewer task was again superior to updating during the display task. In Experiment 4, we found no difference in updating between active and passive self-movement. These results are discussed in terms of differences in sources of extraretinal information available in each movement condition.

Humans↗

PubMed2003

Updating space during imagined self- and array translations.

Previous work has demonstrated superior spatial updating performance during imagined viewer rotation versus imagined object/array rotation. Studies have also suggested that rotations are more difficult to process than translations. In three studies, we examined whether the advantage seen for updating during imagined self-rotations would generalize to translations. The participants updated the positions of objects in a line extending either to the front and back of the viewer or to the right and left after imagining viewer or array translation. Experiments 1 and 2 replicated the effects seen in imagined rotation tasks. A response time and accuracy advantage was found for imagined viewer translation versus imagined array translation. In Experiment 3, we directly compared real and imagined self- and array translations and demonstrated an advantage for real versus imagined array translation. The results suggest that the advantage for imagined viewer transformations is not a function of the specific transformation, but rather of the ability to imagine and predict the outcome of a moving frame of reference.

Humans↗