1,721,261 research outputs found
Burr, D F, VX44782
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/374979Surname: BURR
Given Name(s) or Initials: D F
Military Service Number or Last Known Location: VX44782
Missing, Wounded and Prisoner of War Enquiry Card Index Number: 29902186360
Item: [2016.0049.07287] "Burr, D F, VX44782
Active movement restores veridical event-timing after tactile adaptation
No full textTomassini A, Gori M, Burr D, Sandini G, Morrone MC. Active movement restores veridical event-timing after tactile adaptation. J Neurophysiol 108: 2092-2100, 2012. First published July 25, 2012; doi: 10.1152/jn.00238.2012.-Growing evidence suggests that time in the subsecond range is tightly linked to sensory processing. Event-time can be distorted by sensory adaptation, and many temporal illusions can accompany action execution. In this study, we show that adaptation to tactile motion causes a strong contraction of the apparent duration of tactile stimuli. However, when subjects make a voluntary motor act before judging the duration, it annuls the adaptation-induced temporal distortion, reestablishing veridical event-time. The movement needs to be performed actively by the subject: passive movement of similar magnitude and dynamics has no effect on adaptation, showing that it is the motor commands themselves, rather than reafferent signals from body movement, which reset the adaptation for tactile duration. No other concomitant perceptual changes were reported (such as apparent speed or enhanced temporal discrimination), ruling out a generalized effect of body movement on somatosensory processing. We suggest that active movement resets timing mechanisms in preparation for the new scenario that the movement will cause, eliminating inappropriate biases in perceived time. Our brain seems to utilize the intention-to-move signals to retune its perceptual machinery appropriately, to prepare to extract new temporal information
Time perception: space-time in the brain
No full textAccurate timing over the sub-second scale is essential for a range of
human perceptual and motor activities, but the mechanisms for
encoding this time scale are poorly understood. Recent work is
suggesting that timing does not involve a centralised clock, but
patterning within a distributed network
Perception: transient disruptions to neural space-time
No full textHow vision operates efficiently in the face of continuous shifts of gaze remains poorly understood. Recent studies show that saccades cause dramatic, but transient, changes in the spatial and also temporal tuning of cells in many visual areas, which may underly the perceptual compression of space and time, and serve to counteract the effects of the saccades and maintain visual stability
Eye movements: Building a stable world from glance to glance
No full textFrequent exploratory eye-movements called saccades pose for the visual system the problem of combining information from successive fixations into an apparently seamless conscious experience. A new study shows that information from successive fixations is combined, not by fusing fixation 'snapshots', but by integrating more complex visual attributes at a mid-high level of analysis
AN ADAPTIVE APPROACH TO SCALE SELECTION FOR LINE AND EDGE-DETECTION
No full textOne of the standard problems of edge- and line-detecting algorithms is to determine the most appropriate size of the convolution-operator for the particular task, maximising the conflicting goals of resolution and sensitivity. Here we suggest a novel approach to scale selection, where the scale size varies dynamically with the convolution output: the stronger the output, the smaller the spatial scale. This principle has been applied to two types of feature-detection algorithms, and shown to perform well for both one- and two-dimensional images
Visual motion distorts visual and motor space
No full textMuch evidence suggests that visual motion can cause severe distortions in the perception of spatial position. In this study, we show that visual motion also distorts saccadic eye movements. Landing positions of saccades performed to objects presented in the vicinity of visual motion were biased in the direction of motion. The targeting errors for both saccades and perceptual reports were maximum during motion onset and were of very similar magnitude under the two conditions. These results suggest that visual motion affects a representation of spatial position, or spatial map, in a similar fashion for visuomotor action as for perception
Collapse of perceptual space during saccades
No full textPurpose To determine where observers locate targets flashed briefly before, during and after saccades Methods Observers made voluntary horizontal saccades (monitored by eye-tracker) from a fixation point on the left of the screen to a target 5, 10 or 20° to the right. They were asked to locate vertical bars of luminance or colour-contrast, flashed briefly (8 ms) before or after the saccade onset, with the aid of a ruler that appeared one second later. Time 0 is defined as the beginning of the saccade. Results (1) Bars before -50 ms or after 70 ms were located veridically and accurately. (2) Bars flashed in the interval of -25 to 0 ms were located at one of two points, depending on its actual spatial position: bars that were to the left of the initial fixation point were seen at that fixation point, while all other were seen at the target. (3) There was a systematic trend towards veridicality as the saccade progressed. (4) Two bars (one upper, one lower) flashed simultaneously at different positions during the interval of -25 to 0 ms were seen as collinear if both were to the right or to the left of fixation. (5) Temporal separation of the two bars could induce apparent spatial separation. Conclusions. Saccades can cause an apparent displacement either in the direction of the saccade or in the opposite direction, depending on the spatial position of the stimulus. These results cannot be explained by a general coordinate shift, continuous or otherwise, since the amount and direction of error in locating a bar depends on its spatial as well as its temporal position. They indicate a collapse of perceptual space along the direction of the saccade towards two attractors, the pre- and post-saccadic fixation points, starting about 25 ms before saccades begin. An attention driven model, incorporating a spatial collapse and a progressive recovery during saccades will be presented
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