Biomedical subjects

Fred W Mast

Publications and source records attributed to Fred W Mast.

3 recordsLinked to original sources

PubMed2003

Visual imagery in cerebral visual dysfunction.

Many sorts of deficits in imagery follow brain damage, but the relation between the site of damage and the type of deficit is not simple or straightforward. The dissociations in performance after brain damage provide hints regarding the processing system underlying imagery, but difficulties in interpretation urge caution in mapping these findings to theoretic models. Neuroimaging techniques, such as PET and fMRI, open a window into the working brain and offer valuable information not easily accessible through the study of patients, who, as noted, may have deficits beyond those observable and may rely on compensation and neural reorganization. As we come to understand the mental imagery system more fully, such issues as the laterality of image generation are likely to prove too coarse and vague. The brain is an enormously intricate organ, and even within a circumscribed domain such as imagery it seems to process information in complex and subtle ways.

Functional Laterality↗

PubMed2003

Four types of visual mental imagery processing in upright and tilted observers.

We investigated the role of body position on performance in four distinct types of mental imagery processing. Previous studies used the upright body position as standard procedure and therefore do not address the issue of whether mental imagery tasks are processed in accordance with ego-centered or gravitational coordinates. In the present study, the subjects were brought into one of three different body positions: upright, horizontal, or supine. In each of these body positions, we measured performance in four imagery tasks, which assessed (1) the ability to generate vivid, high-resolution mental images; (2) the ability to compose mental images from separate parts; (3) the ability to inspect patterns in mental images; and, (4) the ability to mentally rotate patterns in images. Not all processes were affected in the same way when subjects performed them in different body positions. Performance in the image composition and detection tasks depended on body position, whereas there was no such effect for the transformation and resolution tasks.

Adolescent↗

PubMed2002

Visual mental images can be ambiguous: insights from individual differences in spatial transformation abilities.

The debate about whether objects in mental images can be ambiguous has produced ambiguous results. In some studies, participants could not reinterpret objects in images, but even in the studies where participants could reinterpret visualized patterns, the results are not conclusive. The present study used a novel task to investigate the reinterpretation of ambiguous figures in imagery, which required the participants to mentally rotate a figure 180 degrees before attempting to "see" an alternate interpretation. In addition, the participants did not know the purpose of the study in advance, nor did they see alternate interpretations of the stimuli; moreover, we explicitly measured individual differences in key mental imagery abilities. Eight of the 44 participants discovered the alternate version while they were memorizing the figure; 16 reported it after mentally rotating an image; and 20 were not able to "see" the alternate version. The ability to rotate images, assessed with an independent task, was highly associated with reports of image reversals, whereas measures of other imagery abilities were not.

Adolescent↗