Blind spot

About: Blind spot is a research topic. Over the lifetime, 1489 publications have been published within this topic receiving 24764 citations.

Blindsight: A Case Study and Implications

Abstract: PART 1 1. Background 2. D.B.: Clinical history and early testing PART 2 3. Reaching for randomly allocated targets 4. 'Presence' versus 'Absence' 5. Visual acuity 6. Movement thresholds 7. Discrimination of orientation 8. 'Form' discrimination 9. Detection with slow rate of onset 10. The natural blind-spot (optic disc) within the scotoma 11. Left versus right eye 12. Detection of direction of contrast 13. 'Waves' 14. Matching between impaired and intact fields 15. Matching within the impaired field 16. Double associations between form and detection 17. Standard situation PART 3 Review of other cases 19. Status, issues, and implications References Author index Subject index

Interocular rivalry revealed in the human cortical blind-spot representation.

Abstract: To understand conscious vision, scientists must elucidate how the brain selects specific visual signals for awareness. When different monocular patterns are presented to the two eyes, they rival for conscious expression such that only one monocular image is perceived at a time1,2. Controversy surrounds whether this binocular rivalry reflects neural competition among pattern representations or monocular channels3,4. Here we show that rivalry arises from interocular competition, using functional magnetic resonance imaging of activity in a monocular region of primary visual cortex corresponding to the blind spot. This cortical region greatly prefers stimulation of the ipsilateral eye to that of the blind-spot eye. Subjects reported their dominant percept while viewing rivalrous orthogonal gratings in the visual location corresponding to the blind spot and its surround. As predicted by interocular rivalry, the monocular blind-spot representation was activated when the ipsilateral grating became perceptually dominant and suppressed when the blind-spot grating became dominant. These responses were as large as those observed during actual alternations between the gratings, indicating that rivalry may be fully resolved in monocular visual cortex. Our findings provide the first physiological evidence, to our knowledge, that interocular competition mediates binocular rivalry, and indicate that V1 may be important in the selection and expression of conscious visual information.

Role of striate cortex and superior colliculus in visual guidance of saccadic eye movements in monkeys.

Abstract: 1. We studied the effect of lesions placed in striate cortex or superior colliculus on the detection of visual stimuli and the accuracy of saccadic eye movements. The monkeys (Macaca mulatta) first learned to respond to a 0.25 degrees spot of light flashed for 150-200 ms in one part of the visual field while they were fixating in order to determine if they could detect the light. The monkeys also learned in a different task to make a saccade to the spot of light when the fixation point went out, and the accuracy of the saccades was measured. 2. Following a unilateral partial ablation of the striate cortex in two monkeys they could not detect the spot of light in the resulting scotoma or saccade to it. The deficit was only relative; if we increased the brightness of the stimulus from the usual 11 cd/m2 to 1,700 cd/m2 against a background of 1 cd/m2 the monkeys were able to detect and to make a saccade to the spot of light. 3. Following about 1 mo of practice on the detection and saccade tasks, the monkeys recovered the ability to detect the spots of light and to make saccades to them without gross errors (saccades made beyond an area of +/-3 average standard deviations). Lowering the stimulus intensity reinstated both the detection and saccadic errors...

Blind spot viewing system

Abstract: A blind spot viewing system for viewing the blind spot of a vehicle located to the passenger side of the vehicle towards the rear of the vehicle. The system includes a video camera adapted for mounting to the passenger side of the vehicle adjacent the rear of the vehicle. The video camera has a lens facing in an outwards direction from the passenger side of the vehicle to collect images of objects in the driver's passenger side blind spot. A video monitor is electrically connected to the video camera. The video monitor is designed for positioning in the passenger compartment of the vehicle to permit a driver of the vehicle to view images from the video monitor.

Reading with a macular scotoma. I. Retinal location of scotoma and fixation area.

Abstract: To investigate how patients with macular scotomas use residual functional retinal areas to inspect visual detail, a scanning laser ophthalmoscope (SLO) was used to map the retinal locations of scotomas and areas used to fixate. Three patients with dense macular scotomas of at least 20 months duration and with no explicit low vision training were tested. SLO stimuli were produced by computer modulation of the scanned laser beam, and could be placed on known retinal loci by direct observation of the retina on a television monitor. Videotaped SLO images were analyzed to produce retinal maps that are corrected for shifts of stimulus position due to fixational eye movement, thus showing the true retinal locations of scotomas and fixation loci. Major findings were as follows: 1) each patient used a single, idiosyncratic retinal area, immediately adjacent to the scotoma to fixate, and did not attempt to use the nonfunctional foveola, 2) fixation stability with the eccentric fixation locus was as good as, or better than, that of ocularly normal subjects trying to fixate at comparable eccentricities, 3) fixation stability was not systematically related to clinical visual acuity, and 4) there is good agreement as to the shape and overall size of SLO and standard clinical tangent screen scotoma maps for these three patients.