Biomedical subjects

Dorine Vergilino-Perez

Publications and source records attributed to Dorine Vergilino-Perez.

9 recordsLinked to original sources

PubMed2006

The use of recurrent signals about adaptation for subsequent saccade programming depends on object structure.

Executing sequences of accurate saccadic eye movements supposes the use of signals carrying information about the first saccade for updating the predetermined motor plan of the subsequent saccades. The present study examines the signals used in planning a second saccade when subjects made two successive saccades towards one long or two short peripheral objects displayed before the first saccade execution. Different first eye movement signals could be used: desired eye movement signals, representing the movement necessary for attaining the intended target, or actual eye movement signals, representing the movement actually executed. Experimental dissociation of desired and actual eye movement signals is made possible by adaptive modifications of the first saccade, obtained by transfer of single saccade adaptation, during which the motor vector was progressively modified in response to the systematic intra-saccadic step of a single target. Whether the second saccade used the actual eye movement signal to compensate or not for the adaptive changes in the first saccade depended on which object properties were relevant for saccade planning. Compensation was observed for saccades that aimed for a new object (between-object saccades) because adaptation modifies relative object location. No compensation was observed for saccades that explored an extended object (within-object saccades). Implications for the on-line control of subsequent eye movements are discussed.

Adaptation, Physiological↗

PubMed2006

Between-object and within-object saccade programming in a visual search task.

The role of the perceptual organization of the visual display on eye movement control was examined in two experiments using a task where a two-saccade sequence was directed toward either a single elongated object or three separate shorter objects. In the first experiment, we examined the consequences for the second saccade of a small displacement of the whole display during the first saccade. We found that between-object saccades compensated for the displacement to aim for a target position on the new object whereas within-object saccades did not show compensation but were coded as a fixed motor vector applied irrespective of wherever the preceding saccade landed. In the second experiment, we extended the paradigm to examine saccades performed in different directions. The results suggest that the within-object and between-object saccade distinction is an essential feature of saccadic planning.

Adult↗

PubMed2005

Spatial object representation and its use in planning eye movements.

The eye movements we make to look at objects require that the spatial information contained in the object's image on the retina be used to generate a motor command. This process is known as sensorimotor transformation and has been generally addressed using simple point targets. Here, we investigate the sensorimotor transformation involved in planning double saccade sequences directed at one or two objects. Using both visually guided saccades toward stationary objects and objects subjected to intrasaccadic displacements, and memory-guided saccades, we found that the coordinate transformations required to program the second saccade were different for saccades aimed at a new target object and saccades that scanned the same object. While saccades aimed at a new object were updated on the basis of the actual eye position, those that scanned the same object were performed with a fixed amplitude, irrespective of the actual eye position. Our findings demonstrate that different abstract representations of space are used in sensory-to-motor transformations, depending on what action is planned on the objects.

Adult↗

PubMed2004

Object structure and saccade planning.

When orienting to a newly appearing display, evidence shows that two saccadic eye movements are often prepared together. By looking the relation between the landing positions of the first and the second saccade, we examine the frame of reference used for the preparation of the second saccade aiming for a new object or exploring within the same object. We demonstrate that the action to be performed on the object affects the coding of the second saccade. A second saccade directed to a new object is coded to aim for a target position on it and is adjusted to the landing position of the first saccade, whereas a second saccade within the same object is coded as a fixed motor vector applied irrespective of the initial landing position on the object.

Attention↗

PubMed2004

Eye movements when reading disappearing text: is there a gap effect in reading?

Readers' eye movements were monitored when they read either normal sentences or sentences with masked or disappearing text (in which the fixated word disappeared or was masked after 60 ms). The goals of the research were to investigate (1) whether a gap effect occurred in reading and (2) the influence of linguistic and visual factors on oculomotor control. The results of a number of global analyses of eye movements under disappearing text conditions clearly demonstrated that there is no gap effect in reading. However, comparative analyses across a number of local measures in the experiments indicated that cognitive/lexical processes, as well as the continual uptake of visual information, influence eye movement control during reading. A persistent visual object throughout fixation caused refixations and even when a fixated word had disappeared (or been masked), there were significant effects of word frequency and word length.

Cognition↗

PubMed2004

Decision and metrics of refixations in reading isolated words.

Eye movements were recorded during the reading of long words presented in isolation. Overall, the decision to refixate was found to depend on both length and frequency of the word, while refixation amplitude depended only on word length. This finding corroborates the assumption that most refixation saccades are preplanned on the basis of the parafoveal word length. However, cancellation of such a plan is possible and could be linked to the lexical processing during the first fixation into the word. Finally, a small proportion of refixations are corrective saccades, related to an oculomotor error. Theoretical implications for models of eye movement control during reading are discussed.

Cognition↗

PubMed2004

The ability of the saccadic system to change motor plans in scanning letter strings.

Evidence from recent studies bolsters the idea of preestablished motor plans in scanning isolated items. Thus, refixation saccades are preplanned at the same time as the primary saccade directed to a peripheral item and are completed with fixed amplitudes irrespective of the first fixation position in the item. In order to examine the saccadic system's ability to correct the motor plan during its execution on the basis of new visual information, an experiment was conducted in which 11-letter strings were changed to two 5-letter strings at different times after the primary saccade was directed to the stimulus. The results demonstrate that the saccadic system is able to cancel the preplanned refixation saccade and plan a saccade directed to the next item only when the new visual information is available at least 220 msec before the execution of the saccade.

Fixation, Ocular↗

PubMed2003

Foveal stimulation and saccadic latencies.

We investigated how a postsaccadic visual error affects the latency of the subsequent saccade. Observers made sequences of saccades directed to a single object or three separate objects, which could be displaced backward or onward during the primary saccade. The results showed an increase of second saccade latency after a backward displacement and a decrease of second saccade latency after an onward displacement. Moreover, second saccade latencies were particularly short after an onward displacement which resulted in a primary saccade landing position outside the boundary of the objects. We interpret the latency differences in terms of known effects within the saccadic system, specifically the sensitivity to the pattern of visual stimulation, particularly at and near the fovea, and the inverse correlation between secondary saccade amplitudes and secondary saccade latencies.

Fovea Centralis↗

PubMed2003

Reading disappearing text: cognitive control of eye movements.

Participants read sentences containing high- or low-frequency target words under normal reading conditions or disappearing-text conditions (in which the word that was fixated disappeared after 60 ms). Even though the fixated word had disappeared after 60 ms, there was still a robust frequency effect wherein readers fixated longer on low-frequency words than on high-frequency words. Thus, the results are consistent with cognitive-control models of eye movement control and inconsistent with visual/oculomotor-control models. Although the uptake of visual information is clearly important for reading, it is the cognitive processes associated with understanding the fixated words that drive the eyes through the text.

Adolescent↗