Functional neuroimaging in human subjects and single cell recordings in monkeys show that several extra-striate visual areas are activated by visual motion. However, the extent to which different types of motion are p...Functional neuroimaging in human subjects and single cell recordings in monkeys show that several extra-striate visual areas are activated by visual motion. However, the extent to which different types of motion are processed in different regions remains unclear, although neuropsychological studies of patients with circumscribed lesions hint at regional specialization. We, therefore, studied four patients with unilateral damage to different regions of extrastriate visual cortex on a series of visual discrimination tasks that required them, to a different extent, to integrate local motion signals in order to correctly perceive the direction of global motion. Performance was assessed psychophysically and compared with that of control subjects and with the patients’performance with stimuli presented in the visual field ipsilateral to the lesion. The results indicate considerable regional specialization in extra-striate regions for different aspects of motion processing, namely the largest displacement from frame to frame (D-max) that can sustain perception of coherent motion; perception of relative speed; the amount of coherent motion needed to sustain a percept of global motion in a particular direction; the detection of discontinuities within a moving display; the extraction of form from motion. It was also clear that a defect in local motion, i.e. D-max, can be overcome by integrating local motion signals over a longer period of time. Although no patient suffered from only one defect, the overall pattern of results strongly supports the notion of regional specialization for different aspects of motion processing.展开更多
This study was undertaken to develop and test a 3-di-mensional(3D)color thickness mapping technique o nlevator ani imaged with magnetic resonance imaging(MRI ).Supine MRI datasets from 30women were studied:10asymptoma...This study was undertaken to develop and test a 3-di-mensional(3D)color thickness mapping technique o nlevator ani imaged with magnetic resonance imaging(MRI ).Supine MRI datasets from 30women were studied:10asymptomatic,10with urodynamic stress incontinence,and 10with pelvic organ prolapse.Levators were manually outlined,and thickness mapping applied.Three -dimen-sionalmodelswere colored topograp hically,reflecting levator thickness.Thickness and occurrences of absent levator substance(gaps)were compared across the 3groups,us-ing nonparametric statistical tests.Color thickness mapping was successful in all subjects.There were statistically sig-nificant differences in thickness a nd gap percentages among the 3groups of women,with thicker,b ulkier levators in asymptomatic women,compared with w omen with prolapse or urodynamic stress incontinence.Color thickness map-ping is feasible.It may be used to com pare levators in symptomatic and asymptomatic women,to study relation-ships between levator thickness and pelvic floor dysfunc-tion.This technique can be used in la rger studies for hy-pothesis testing.展开更多
文摘Functional neuroimaging in human subjects and single cell recordings in monkeys show that several extra-striate visual areas are activated by visual motion. However, the extent to which different types of motion are processed in different regions remains unclear, although neuropsychological studies of patients with circumscribed lesions hint at regional specialization. We, therefore, studied four patients with unilateral damage to different regions of extrastriate visual cortex on a series of visual discrimination tasks that required them, to a different extent, to integrate local motion signals in order to correctly perceive the direction of global motion. Performance was assessed psychophysically and compared with that of control subjects and with the patients’performance with stimuli presented in the visual field ipsilateral to the lesion. The results indicate considerable regional specialization in extra-striate regions for different aspects of motion processing, namely the largest displacement from frame to frame (D-max) that can sustain perception of coherent motion; perception of relative speed; the amount of coherent motion needed to sustain a percept of global motion in a particular direction; the detection of discontinuities within a moving display; the extraction of form from motion. It was also clear that a defect in local motion, i.e. D-max, can be overcome by integrating local motion signals over a longer period of time. Although no patient suffered from only one defect, the overall pattern of results strongly supports the notion of regional specialization for different aspects of motion processing.
文摘This study was undertaken to develop and test a 3-di-mensional(3D)color thickness mapping technique o nlevator ani imaged with magnetic resonance imaging(MRI ).Supine MRI datasets from 30women were studied:10asymptomatic,10with urodynamic stress incontinence,and 10with pelvic organ prolapse.Levators were manually outlined,and thickness mapping applied.Three -dimen-sionalmodelswere colored topograp hically,reflecting levator thickness.Thickness and occurrences of absent levator substance(gaps)were compared across the 3groups,us-ing nonparametric statistical tests.Color thickness mapping was successful in all subjects.There were statistically sig-nificant differences in thickness a nd gap percentages among the 3groups of women,with thicker,b ulkier levators in asymptomatic women,compared with w omen with prolapse or urodynamic stress incontinence.Color thickness map-ping is feasible.It may be used to com pare levators in symptomatic and asymptomatic women,to study relation-ships between levator thickness and pelvic floor dysfunc-tion.This technique can be used in la rger studies for hy-pothesis testing.
