Biomedical subjects

Jeffrey M Zacks

Publications and source records attributed to Jeffrey M Zacks.

5 recordsLinked to original sources

PubMed2003

Selective disturbance of mental rotation by cortical stimulation.

In order to plan activity, people must imagine the spatial consequences of potential actions. Two classes of mental spatial transformation can be distinguished: Object-based spatial transformations are imagined movements of objects, such as mental rotation. Egocentric perspective transformations are imagined changes in one's viewpoint, such as imagining one's self in the position of another person. Here we report a case in which electrical stimulation of the right parietal cortex selectively interfered with performance of a mental rotation task. Interference was selective to this stimulation site, and was task specific. Performance of the perspective transformation task, and a control for visual encoding and responding, were unimpaired by stimulation. This marks the first instance of the use of direct cortical stimulation to investigate mental spatial transformations.

Adult↗

PubMed2003

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.g., head of a wrench fused onto a sheep body). To maximize surprise we administered novel incongruent pictures infrequently in an initial scan. (This scan also included infrequent color-inverted pictures as a control for frequency.) To obtain a pure measure of the effect of incongruity we conducted a second scan in which participants viewed equal numbers of ordinary and incongruous pictures. Signal increases were greater for incongruous versus ordinary and oddball stimuli throughout the ventral and dorsal visual pathways, and in prefrontal cortex bilaterally. Signal decreases were larger for incongruous than for ordinary stimuli bilaterally in lateral parietal regions. A subset of regions near the right frontal operculum and extending laterally responded only to, or more strongly to, infrequent incongruous pictures. A second, purely behavioral, experiment involving a separate group of participants demonstrated that incongruous pictures were better recognized than ordinary pictures. We interpret our results as suggesting that, although correlates of a surprise response can be observed, better memory for incongruous visual information is attributable mainly to more processing and, consequently, better encoding.

Adult↗

PubMed2003

Structuring information interfaces for procedural learning.

Interface design should be informed by the application of top-down cognitive principles derived from basic theory and research. Cognitive design principles from 2 domains, event cognition and media, were applied to the design of interfaces for teaching procedures. According to theories of event cognition, procedures should be presented hierarchically, organized by objects or large object parts and actions on objects. According to research on effects of media, adding appropriate graphics to text instructions can facilitate learning and memory. These principles were partially supported in 2 tasks: assembling a musical instrument and building a model. Although both top-down principles were effective in guiding interface design, they were not sufficient. They can be combined with iterative bottom-up methods to produce usable interfaces.

Adolescent↗

PubMed2002

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. If priming can be due to both unshared and shared components of imagery and perception, then it should be possible to observe greater priming from imagery than from perception. Two new priming experiments were designed to test this hypothesis, while controlling incidental task differences. In both experiments, participants studied objects by counting their parts (from a mental image or a picture). Experiment 1 used a word-picture matching test task, which was hypothesized to depend on stimulus processing specific to perception, and Experiment 2 a size judgment test task, which was hypothesized to depend on retrieval and generation processes specific to imagery. As predicted, priming for perceived objects was greater than priming for imagined objects in the word-picture matching task. Conversely, in the size judgment task, more priming from imagery than from perception was observed. These results support the conclusions that (a) imagery and perception have substantial unshared processes, and (b) these processes contribute to priming.

Adult↗

PubMed2002

A parametric study of mental spatial transformations of bodies.

TWO CLASSES OF MENTAL SPATIAL TRANSFORMATION CAN BE DISTINGUISHED: Object-based spatial transformations are imagined movements of objects; and egocentric perspective transformations are imagined movements of one's point of view. The hypothesis that multiple neural systems contribute to these mental imagery operations was tested with functional MRI. Participants made spatial judgments about pictures of human bodies, and brain activity was analyzed as a function of the judgment required and the time taken to respond. Areas in right temporal, occipital and parietal cortex and the medial superior cerebellum appear to be differentially involved in object-based spatial transformations. Additionally, midline structures and lateral parietal cortex were found to decrease in activity during the spatial reasoning tasks, independently of the judgment required or of the latency of response. The results are discussed in terms of a model of spatial reasoning that postulates specialized subsystems for performing object-based and egocentric perspective image transformations.

Adult↗