Biomedical subjects

Stefan Van der Stigchel

Publications and source records attributed to Stefan Van der Stigchel.

8 recordsLinked to original sources

PubMed2006

The spatial coding of the inhibition evoked by distractors.

It is generally agreed that saccade deviations away from a distractor location represent inhibition in the oculomotor system. By systematically manipulating the location of a distractor we tested whether the inhibition of the distractor is coded coarsely or fine-grained. Results showed that the location of a distractor had an effect on the saccade trajectories, suggesting that the amount of inhibition observed depends on the location of the distractor. More specifically, the vertical distance of the distractor from fixation seems to be a determining factor. These findings have important implications for models that account for inhibition in the target selection process and the areas that could underlie inhibitory influences on the superior colliculus (SC), like the frontal eye fields (FEF) and the dorsolateral prefrontal cortex (dlPFC). Finally, the initial direction and the endpoint of a saccade were found to be strongly correlated, which contradicts recent models proposing that the initial saccade direction and saccade endpoint are unrelated.

Adolescent↗

PubMed2006

Top-down influences make saccades deviate away: the case of endogenous cues.

We tested a recent hypothesis suggesting that the eye deviates away from a location when top-down preparation can influence target selection. Participants had to make an eye movement to a peripheral target. Before the upcoming target, a central cue indicated the likely target location. Results show that when the target was presented at a location different from that indicated by the cue, eye movements to the target deviated away from the cued location. Because central cues are under top-down control, the present results are in line with a determining role of top-down preparation on saccade direction. These results contrast with the findings reported in a similar paradigm executed with hand movements, in which the movements were mostly initiated in the direction of the cued location. Therefore, we conclude that inhibitory effects typically observed when executing eye movements may not be observed when executing hand movements in similar conditions.

Adult↗

PubMed2006

An ERP study of preparatory and inhibitory mechanisms in a cued saccade task.

The present study uses event-related potentials (ERPs) to investigate the neurophysiological correlates of the mechanisms involved in selection of locations for saccades. Participants performed a task in which both target and distractor locations were cued on a trial-by-trial basis. Participants were instructed to make an eye movement to the cued target location and to ignore elements at the distractor location. This experimental set-up allowed the investigation of the mechanisms involved in the top-down preparation and inhibition of locations for an eye movement. When comparing responses to leftward and rightward pointing cues, we observed an early directing attention negativity (EDAN) and an anterior directing attention negativity (ADAN) effect in the cue-target interval. These effects were similar to those observed in studies investigating attentional allocation, suggesting a close link between shifts of spatial attention and the preparation of eye movements. These components were followed by a late widespread contralateral negativity (LDAN) that was assumed to reflect both the oculomotor programming of the upcoming eye movement as well as attentional orienting. Furthermore, a new component was observed related to top-down inhibition of the distractor location. In response to the distractor cue, an early positivity above the right hemisphere (RLIP) was revealed. Finally, no modulations of early target-evoked ERP components were observed, suggesting that these components are unaffected when no further processing is required at the cued location.

Adult↗

PubMed2006

Eye movement trajectories and what they tell us.

In the last two decades, research has shown that eye movement trajectories can be modified by situational determinants. These modifications can inform us about the mechanisms that control eye movements and they can yield information about the oculomotor, memory and attention system that is not easily obtained via other sources. Eye movement trajectories can deviate either towards or away from elements in the visual field. We review the conditions in which these deviations are found and the mechanisms underlying trajectory deviations. It is argued that deviations towards an element are caused by the unresolved competition in the oculomotor system between elements in a visual scene. Deviations away from an element are mainly observed in situations in which top-down preparation can influence the target selection process, but the exact cause of such deviations remains unclear.

Attention↗

PubMed2006

Spatial working memory and inhibition of return.

Recently we showed that maintaining a location in spatial working memory affects saccadic eye movement trajectories, in that the eyes deviate away from the remembered location (Theeuwes, Olivers, and Chizk, 2005). Such saccade deviations are assumed to be the result of inhibitory processes within the oculomotor system. The present study investigated whether this inhibition is related to the phenomenon of inhibition of return (IOR), the relatively slow selection of previously attended locations as compared with new locations. The results show that the size of IOR to a location was not affected by whether or not the location was kept in working memory, but the size of the saccade trajectory deviation was affected. We conclude that inhibiting working memory-related eye movement activity is not the same as inhibiting a previously attended location in space.

Humans↗

PubMed2005

Our eyes deviate away from a location where a distractor is expected to appear.

Previous research has shown that in order to make an accurate saccade to a target object, nearby distractor objects need to be inhibited. The extent to which saccade trajectories deviate away from a distractor is often considered to be an index of the strength of inhibition. The present study shows that the mere expectation that a distractor will appear at a specific location is enough to generate saccade deviations away from this location. This suggests that higher-order cognitive processes such as top-down expectancy interact with low-level structures involved in eye movement control. The results will be discussed in the light of current theories of target selection and possible neurophysiological correlates.

Adolescent↗

PubMed2005

Relation between saccade trajectories and spatial distractor locations.

This study shows that the exact spatial location of a distractor can have a modulatory influence on saccade trajectories. Distractors close to the target evoke saccade trajectories that are directed towards the distractor, while distractors close to fixation result in saccades that are directed away from the distractor. This finding questions the idea that target positions are coarsely coded in the superior colliculus.

Functional Laterality↗

PubMed2005

The influence of attending to multiple locations on eye movements.

The present paper reports results of a dual task study in which two locations were endogenously cued as possible target locations, while only one eye movement had to be executed. During the cue period, letters were briefly presented at the saccade goals and at no-saccade goals. Results show that performance was better for letters presented at any of the saccade goals than for letters presented at the no-saccade locations. Furthermore saccades deviated away from the non-saccaded target location, suggesting inhibition of the location to which the eyes should not go. The results indicate that the premotor theory also holds for conditions in which attention is allocated to multiple locations.

Adolescent↗