Comparison of the haptic and visual deviations in a parallelity task

Deviations in both haptic and visual spatial experiments are thought to be caused by a biasing influence of an egocentric reference frame. The strength of this influence is strongly participant-dependent. By using a parallelity test, it is studied whether this strength is modality-independent. In both haptic and visual conditions, large, systematic and participant-dependent deviations were found. However, although the correlation between the haptic and visual deviations was significant, the explained variance due to a common factor was only 20%. Therefore, the degree to which a participant is “egocentric” depends on modality and possibly even more generally, on experimental condition

The haptic perception of spatial orientations

This review examines the isotropy of the perception of spatial orientations in the haptic system. It shows the existence of an oblique effect (i.e., a better perception of vertical and horizontal orientations than oblique orientations) in a spatial plane intrinsic to the haptic system, determined by the gravitational cues and the cognitive resources and defined in a subjective frame of reference. Similar results are observed from infancy to adulthood. In 3D space, the haptic processing of orientations is also anisotropic and seems to use both egocentric and allocentric cues. Taken together, these results revealed that the haptic oblique effect occurs when the sensory motor traces associated with exploratory movement are represented more abstractly at a cognitive level

Perceived frequency of aperiodic vibrotactile stimuli depends on temporal encoding

Mechanical transients and events arising during dexterous manipulation are detected by tactile afferents. Naturally occurring vibrotactile stimuli have a mix of frequencies, which creates complex afferent discharge patterns. Psychophysical correlates of these complex discharge patterns could be useful tools to gain greater insights into tactile coding and the principles of signal processing in the nervous system. In a previous study, we discovered that frequency perception of periodic bursting stimuli depended on the duration of the silent gap between spike bursts. Here, we investigated the perceived frequency of aperiodic vibrotactile stimuli. We found that perceived frequency was lower than the mean discharge rate of the afferents. This supports a hypothesis stemming from our previous work, that within spike trains consisting of mixed length inter-spike intervals, the contribution of a given interval to perceived frequency is weighted by its length. Thus, the present study reveals that frequency perception of both periodic and aperiodic stimuli is encoded by sophisticated processing of individual inter-spike intervals, rather than based on detection of periodicity or spike counting

A model of contextual effect on reproduced extents in recall tasks: the issue of the imputed motion hypothesis

In this article the fundamental question of space and time dependencies in the reproduction of spatial or temporal extents is studied. The functional dependence of spatial responses on the temporal context and the corresponding dependence of temporal responses on spatial context are reported as the tau and kappa effects, respectively. A common explanation suggested that the participant imputes motion to discontinuous displays. Using a mathematical model we explore the imputed velocity hypothesis and provide a globally fit model that addresses the question of sequences modelling. Our model accounts for observed data in the tau experiment. The accuracy of the model is improved introducing a new hypothesis based on small velocity variations. On the other hand, results show that the imputed velocity hypothesis fails to reproduce the kappa effect. This result definitively shows that both effects are not symmetric.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe