Biomedical subjects

F Gaunet

Publications and source records attributed to F Gaunet.

7 recordsLinked to original sources

PubMed2001

Active, passive and snapshot exploration in a virtual environment: influence on scene memory, reorientation and path memory.

We investigated the importance of active, passive and snapshot exploration on spatial memory in a virtual city. The exploration consisted in traveling along a series of streets. 'Active exploration' was performed by giving directions to the subject who controlled his displacement with a joystick. During 'passive' exploration, the travel was imposed by the computer. Finally, during 'snapshot exploration', simple views of the scene were presented sequentially every 4 m. Travel velocity was the same in all cases. The three visual exploration modes were compared with three spatial memory measures: (1) scene recognition, (2) at the end of the path, reorientation toward the departure point and (3) drawings of the path shape. Scene recognition and estimation of the direction of the starting point of the path were not affected by the mode of exploration. In contrast, reproduction of the shape of the path was affected: the errors of reproduction were greater for the snapshot exploration than for the other two conditions; there was no difference between the other two conditions. These results suggest that (1) 2D image features from a visual scene are memorized. Moreover, (2) pointing towards the origin of the path relies on motion duration integration or a frame of reference integrated during displacement. Finally, (3) drawing the path shape involves a deliberate reconstruction process.

Adult↗

PubMed2000

Mental rotation for spatial environment recognition.

We investigated the importance of retinal and body inclination in the recognition of spatial environment. The paradigm involved the recognition, in body upright and tilted conditions, of tilted images -intervals of 15 degrees from 0 degrees to 90 degrees leftward and rightward respective to head coordinates - of known spatial layouts encountered while walking in Paris. The analysis of reaction times was consistent with the subjects mentally rotating the spatial layout so that the environment was subjectively vertical before making their decisions. In contrast, when the body was roll-tilted (33 degrees ), overall reaction time was not affected; however, reaction time and spatial layout tilt with respect to the head were correlated when the body was tilted but not when upright. Both results indicate that gravity was slightly important in performing the task.

Adult↗

PubMed1999

Spatial performance of unilateral vestibular defective patients in nonvisual versus visual navigation.

The purpose of this study was to investigate the effects of unilateral vestibular neurotomy on humans ability to perform navigation tasks. These tasks provided self-motion feedback by way of either locomotor activity only (nonvisual navigation or "locomotor task") or visual motion cues only (visually simulated navigation or "visual task"). After exploration of an environment in which 4 locations were marked by different objects, subjects attempted to navigate to those locations either by reproducing the same paths as those followed during exploration, by reversing routes, or by making spatial inferences (shortcuts). Vestibular defective patients were tested one day before surgical treatment and during the recovery time course following unilateral vestibular nerve lesion (1 week, 1 month, and 3 month later). Their performance was assessed by measuring turn error and distance error in both navigation tasks and was compared to that of control subjects tested 4 times at similar time intervals. Turn error in the reproduction of previously explored routes in the locomotor task was lower in patients before surgery than in controls, suggesting the existence of compensatory processes. In the acute stage (1 week) after unilateral vestibular lesion, turn error was greater in patients than in controls for the highest level of mental representation (spatial inferences or reversing routes); impairment at making accurate rotations had disappeared by 1 month after vestibular lesion in both navigation tasks. These results point to the role of vestibular cues, in interaction with other sensory modalities, in the elaboration of an accurate internal representation of the environment. In addition, they suggest that unilateral suppression of vestibular information would induce transitory spatial memory disorganization at a high level of information processing.

Distance Perception↗

PubMed1997

Representation of space in blind persons: vision as a spatial sense?

Some researchers of studies of the incidence of early visual experience on spatial abilities have demonstrated profound spatial deficits in early blind participants, whereas others have not found evidence of deleterious effects of early visual deprivation. The aims of this article are to (a) consider the theoretical background of these studies, (b) take stock of the divergent data, and (c) propose new means of investigation. The authors examine the reasons why vision plays a critical role in spatial cognition. They review the literature data. They also review the factors that could account for the discrepant data and the effects of lack of early visual experience on brain functioning. They propose that the study of strategies is a valuable option to obtain insight into early blind persons' spatial impairment.

Blindness↗

PubMed1997

Early-blind subjects' spatial representation of manipulatory space: exploratory strategies and reaction to change.

The present study was aimed at analysing the effects of a lack of visual experience in human subjects on the detection and identification of a spatial change brought about to a configuration of objects displayed in manipulatory space. Exploratory patterns and performance levels were recorded. Learning effects were observed in different types of change and condition of presentation only in the early-blind and blindfolded sighted groups, but not in the late-blind group. Early blindness affected both exploratory patterns and performance levels. In addition, significant correlations were found between performance level and the use of systematic patterns of exploration. These data are discussed in relation with the importance of early vision during the development of spatial cognition.

Adolescent↗

PubMed1996

Early visual experience affects memorization and spatial representation of proprioceptive targets.

Five subjects who had been blind from an early age and five age-matched blindfolded sighted subjects were engaged in a spatial memory task. Locations to be memorized were presented on a sagittal plane by passive positioning of the left index finger. A go signal for matching the target location with the right index finger was provided 0 or 8 s after left hand positioning. Constant errors in amplitude and direction of movement and pointing distribution observed after the longer delay differed across groups. Pointing variability was higher in the blindfolded sighted group. In addition, the main axis of pointing distributions obtained in the blindfolded sighted group were aligned with the target array for the 8 s but not the 0 s delay. By contrast, the main axis tended to be aligned with movement direction for blind subjects for both delays. These results suggest that memorizing a proprioceptively defined target may involve distinct spatial representations according to delay and to early visual experience.

Adult↗

PubMed1996

Early-blind subjects' spatial abilities in the locomotor space: exploratory strategies and reaction-to-change performance.

The present study was aimed at analysing the effect of the lack of visual experience in the human subject in detecting the rearrangement of objects after a free exploration in the locomotor space. Exploratory patterns and performance levels were recorded. Distance processing was affected by early blindness. The early-blind group's patterns of exploration differed significantly from those of the visually experienced groups. Significant correlations were found between the performance level and the use of systematic patterns of exploration but not with individual features. These data are discussed in the light of the importance of early vision on the development of spatial cognition.

Adolescent↗