Biomedical subjects

P Péruch

Publications and source records attributed to P Péruch.

3 recordsLinked to original sources

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

Homing in virtual environments: effects of field of view and path layout.

Triangle completion (ie homing to the starting point after completing two legs of a triangle) is a widely used method for examining path-integration abilities in animals and humans. Two experiments are reported in which homing was used to examine the efficiency of purely visual mechanisms (eg optical flow) for spatial-information coding and integration. Adult observers had to complete triangles in an interactively simulated three-dimensional environment which consisted of two critical objects and a homogeneous set of white cylinders serving as background. Each participant completed twenty-seven triangles corresponding to a factorial combination of three geometrical fields of view (40 degrees, 60 degrees, or 80 degrees) and nine triangle layouts (with variations of the first turning angle and the second leg). Homing performances revealed strong effects of triangle layout, but no effect of geometrical fields of view: variations in the amount of simultaneous visible spatial information did not influence the acquisition of spatial knowledge in the environments used. Applying the encoding-error model to the data revealed severe systematic errors of picking up directional information while moving through visually simulated environments. These results are discussed with respect to informational differences between situations of purely visual and nonvisual navigations in space.

Adult↗

PubMed1993

Route knowledge in different spatial frames of reference.

Orienting oneself in space requires establishing a correspondence between various spatial frames of reference (SFR) in which the same information about the environment can be encoded in different ways and formats. In this encoding process, one key point is the alignment of the SFRs, which may require additional operations such as a mental or real rotation. Three experiments were conducted to investigate the process of spatial orientation under aligned and misaligned conditions. Subjects were shown animated sequences of decision points perceived along a route (Experiments 1 and 2) or verbal route instructions (Experiment 3) to which they had to attribute a path on a map. The results showed that when the orientations of the map and the route were different (misalignment) both total time and errors increased. The route length (Experiment 1), and the need to reverse the direction of the path (reverse response condition in Experiments 2 and 3) also led to a decline in performance. In Experiment 3, the map-rotation strategy was found to be pertinent for solving misaligned spatial problems.

Adult↗