PubMed · 7339571
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P J McAdie, M J Steinbach. 1981. Visually induced tilt affects form perception.. https://doi.org/10.1068/p100525
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We investigated in humans whether the shift of the beating field, which is often observed during vestibular nystagmus, could be related to some strategy of orientation. Eye movements were measured with an infrared system during an experiment on self-motion perception in the dark. Subjects were asked to rotate, by means of a joystick, a mobile robot on which they were seated in order to reproduce a previously imposed passive rotation. We suggest that the shift of the ocular beating field is the manifestation of two different orientation strategies based on allocentric and egocentric reference frames, respectively. It is also proposed that subjects who preferably used the first strategy exhibited large shifts of the beating field, while the others who probably used egocentric memory did not exhibit any shift.
A quantitative analysis of various fetal activities (mouth, eye and gross body movements) was made in 10 IUGR human fetuses. The aim of the study was to see whether IUGR fetuses move differently to normal fetuses. Each real-time ultrasound recording lasted 1 h and the analysis of various activities was carried out during replay of video recordings by means of a specially designed computer program. The following aspects have been investigated: (1) incidence, duration and interval for each of the fetal activities described; (2) the relationship between incidence, duration and interval for each single activity; (3) the correlations between the different activities. The results were compared with a group of 10 fetuses from normal pregnancies. On quantitative evaluation no clear effects due to uncomplicated IUGR could be detected except for median duration of eye movements, which turned out to be longer in the IUGR group. The evaluation of correlations between the characteristics (incidence, duration and interval) of each activity showed a positive correlation between incidence and duration of mouthing movements in the IUGR group, not found in the normal group. The study of the correlation between different fetal activities has shown an inverse correlation between mouthing and other activities in the normal fetuses, not found in the IUGR group. We conclude that in mildly affected fetuses with no evidence of hypoxia, there are no quantitative differences compared to normal fetuses in terms of the motility studied. The only differences found were in relation to the performance of such activities and they could reflect a dysfunction of the central nervous system resulting from a metabolic disturbance.
Information from the auditory and visual systems converges in the nervous system with physiological and behavioral consequences. Most of our knowledge about the rules governing such convergence has been obtained in experiments where the strength or the timing of the individual auditory and visual stimuli has been varied. Relatively little attention has been paid to the spatial relationship between different modalities of stimuli in multisensory experiments. We studied saccadic reaction times of human subjects to bimodal auditory and visual stimulus presentations under two conditions: first, with the targets spatially coincident and, second, with various degrees of spatial separation or disparity. In the first experiment, we found that the saccadic reaction times were consistently shorter than would be predicted by independent processing of information about the visual and auditory targets. These results suggest convergence of multimodal information at one or more loci within the nervous system. In the second experiment, we found that saccadic latency gradually increased as spatial distance between the auditory and visual targets increased. Evidence for neural summation was found over a wide range of spatial disparities. These results suggest that multisensory information can be integrated and have significant influences on behavior over a surprisingly large range of spatial disparity.