Biomedical subjects

Daniel V Meegan

Publications and source records attributed to Daniel V Meegan.

4 recordsLinked to original sources

PubMed2006

The effect of the Müller-Lyer illusion on the planning and control of manual aiming movements.

Two experiments used Müller-Lyer stimuli to test the predictions of the planning-control model (S. Glover, 2002) for aiming movements. In Experiment 1, participants aimed to stimuli that either remained the same or changed upon movement initiation. Experiment 2 was identical except that the duration of visual feedback for online control was manipulated. The authors found that the figures visible during movement planning and online control had additive effects on endpoint bias, even when participants had ample time to use visual feedback to modify their movements (Experiment 2). These findings are problematic not only for the planning-control model but also for A. D. Milner and M. A. Goodale's (1995) two visual system explanation of illusory bias. Although our results are consistent with the idea that a single representation is used for perception, movement planning, and online control (e.g., V. H. Franz, 2001), other work from our laboratory and elsewhere suggests that the manner in which space is coded depends on constraints associated with the specific task, such as the visual cues available to the performer.

Adult↗

PubMed2005

Spatial information is processed even when it is task-irrelevant: implications for neuroimaging task design.

Many neuroimaging studies have been designed to differentiate domain-specific processes in the brain. A common design constraint is to use identical stimuli for different domain-specific tasks. For example, an experiment investigating spatial versus identity processing would present compound spatial-identity stimuli in both spatial and identity tasks, and participants would be instructed to attend to, encode, maintain, or retrieve spatial information in the spatial task, and identity information in the identity task. An assumption in such studies is that spatial information will not be processed in the identity task, as it is irrelevant for that task. We report three experiments demonstrating violations of this assumption. Our results suggest that comparisons of spatial and identity tasks in existing neuroimaging studies have underestimated the amount of brain activation that is spatial-specific. For future neuroimaging studies, we recommend unique stimulus displays for each domain-specific task, and event-related measurement of post-stimulus processing.

Adult↗

PubMed2004

Task analysis complements neuroimaging: an example from working memory research.

When functional neuroimaging researchers draw conclusions about the sensory, cognitive, or motor processes that are associated with changes in brain activity, they are making assumptions about the component processes involved in performing a complex behavioral task. We demonstrate the danger in making such assumptions using, as an example, the n-back task, which has been widely used in neuroimaging studies of working memory. Neuroimaging researchers have assumed that the letter n-back task only engages processes involved in the short-term maintenance and manipulation of verbal information. We report three behavioral experiments demonstrating that the letter n-back task additionally recruits spatial processes. A fourth experiment suggested that the location n-back task may recruit verbal processes in addition to spatial processes. These results call into question conclusions that have been drawn about the neural basis of working memory. More broadly, our results demonstrate that task analysis is a vital partner of neuroimaging in the cognitive neuroscience enterprise.

Acoustic Stimulation↗

PubMed2003

The Müller-Lyer illusion affects the planning and control of manual aiming movements.

Participants made perceptual judgments about the length of, and manual aiming movements to the opposite end of, formerly visible Müller-Lyer stimuli. The Müller-Lyer illusion affected both perceptual judgments and aiming amplitude. Manipulations of stimulus duration (10 ms or 3000 ms) and memory delay length (10 ms or 3000 ms) had no impact on the illusory effect. Aiming movements executed with vision of the hand were less affected by the illusion than movements executed without vision of the hand. The effect of the illusion on aiming amplitude remained the same between peak velocity and the end of the movement even though participants were engaged in on-line control between peak deceleration and the end of the movement. This latter finding was counter to the predictions of a hypothesis (Glover 2002) stating that illusions should only affect the early (planning) stages of movement and not the late (control) stages of movement. We conclude that a single visual representation is used for perception, motor planning, and motor control.

Adult↗