The Ferrier Lecture, 1989 - Outlooks for blindsight: explicit methodologies for implicit processes

1990 ◽  
Vol 239 (1296) ◽  
pp. 247-278 ◽  
Keyword(s):  
Visual Field ◽  
Striate Cortex ◽  
Human Subjects ◽  
Visual Stimuli ◽  
Forced Choice ◽  
Visual Field Defects ◽  
Implicit Processes ◽  
Human Infants ◽  
Parallel Pathways ◽  
Skin Response

In primates the retina is connected with different targets in the brain via several parallel pathways, the largest of which is that going to the lateral geniculate nucleus of the thalamus and thence to the striate cortex, the geniculo-striate pathway. When this route is damaged in man, apparent blindness in a corresponding part of the visual field occurs, despite the integrity of the other parallel pathways. In animals, it has been demonstrated by conventional behavioural forced-choice techniques that extrastriate routes can sustain a variety of visual discriminations. Comparable discriminations are also possible in some human subjects with geniculostriate damage when forced-choice ‘guessing’ techniques are used. ‘Blind-sight’ refers to those subjects who state that they are unaware of the visual stimuli, even when performing discriminations at high levels of proficiency. Extensions of this approach are reviewed, especially to spec­tral sensitivity and movement discrimination. But residual capacities can also be assessed without requiring guessing responses, thereby avoiding issues of differential response criteria and other practical difficulties. Effects of ‘unseen’ stimuli in the cortically blind field on the visible perception of concurrent stimuli in the intact field can be measured. Also, positive reactions of the autonomic nervous system, such as the galvanic skin response, can be recorded to visual stimuli presented in the blind field. Recent evidence demonstrates that the pupil in normal adult sub­jects is systematically sensitive to structural and chromatic features of visual stimuli. Pupillometry reveals specific changes and residual capaci­ties in visual-field defects of adult patients with striate cortical damage. Thus non-verbal and sensitive methods are available that permit the comparative study of normal and residual visual capacity in human infants, adults and infra-human animals.

Perimetric Study of Field Defects in Monkeys after Cortical and Retinal Ablations

1967 ◽  
Vol 19 (3) ◽  
pp. 232-245 ◽  
Author(s):  
Alan Cowey
Keyword(s):  
Visual Field ◽  
Histological Examination ◽  
Striate Cortex ◽  
Visual Field Defects ◽  
Projection Area ◽  
Central Scotoma ◽  
Eccentric Fixation ◽  
Field Defect ◽  
Primary Projection ◽  
Field Defects

Monocular visual field defects were studied in two monkeys. In one, the macular retina was destroyed by photocoagulation, producing a central scotoma and consistent 5° eccentric fixation. In a second animal the effects of removal of macular projection area in striate cortex and subsequent photocoagulation of the macula were compared. The cortical operation produced a partial field defect, i.e. a region of diminished sensitivity but not a scotoma, which became with practice much smaller than the region of retina whose primary projection area had been ablated. A 10° eccentric fixation was observed. Following the second, retinal, operation a macular scotoma was demonstrated whose size and position corresponded closely with the area of retinal destruction as determined by photography of the fundus and later histological examination of the retina.

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

1977 ◽  
Vol 40 (1) ◽  
pp. 74-94 ◽  
Author(s):  
C. W. Mohler ◽  
R. H. Wurtz
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Superior Colliculus ◽  
Stimulus Intensity ◽  
Macaca Mulatta ◽  
Striate Cortex ◽  
Visual Stimuli ◽  
Saccadic Eye Movements ◽  
Visual Guidance

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...

Both striate cortex and superior colliculus contribute to visual properties of neurons in superior temporal polysensory area of macaque monkey

1986 ◽  
Vol 55 (5) ◽  
pp. 1057-1075 ◽  
Author(s):  
C. J. Bruce ◽  
R. Desimone ◽  
C. G. Gross
Keyword(s):  
Visual Field ◽  
Receptive Field ◽  
Superior Colliculus ◽  
Striate Cortex ◽  
Visual Stimuli ◽  
Receptive Fields ◽  
Visual Responses ◽  
Stimulus Motion ◽  
Visual Hemifields ◽  
Visual Properties

Although the tectofugal system projects to the primate cerebral cortex by way of the pulvinar, previous studies have failed to find any physiological evidence that the superior colliculus influences visual activity in the cortex. We studied the relative contributions of the tectofugal and geniculostriate systems to the visual properties of neurons in the superior temporal polysensory area (STP) by comparing the effects of unilateral removal of striate cortex, the superior colliculus, or of both structures. In the intact monkey, STP neurons have large, bilateral receptive fields. Complete unilateral removal of striate cortex did not eliminate visual responses of STP neurons in the contralateral visual hemifield; rather, nearly half the cells still responded to visual stimuli in the hemifield contralateral to the lesion. Thus the visual properties of STP neurons are not completely dependent on the geniculostriate system. Unilateral striate lesions did affect the response properties of STP neurons in three ways. Whereas most STP neurons in the intact monkey respond similarly to stimuli in the two visual hemifields, responses to stimuli in the hemifield contralateral to the striate lesion were usually weaker than responses in the ipsilateral hemifield. Whereas the responses of many STP neurons in the intact monkey were selective for the direction of stimulus motion or for stimulus form, responses in the hemifield contralateral to the striate lesion were not selective for either motion or form. Whereas the median receptive field in the intact monkey extended 80 degrees into the contralateral visual field, the receptive fields of cells with responses in the contralateral field that survived the striate lesions had a median border that extended only 50 degrees into the contralateral visual field. Removal of both striate cortex and the superior colliculus in the same hemisphere abolished the responses of STP neurons to visual stimuli in the hemifield contralateral to the combined lesion. Nearly 80% of the cells still responded to visual stimuli in the hemifield ipsilateral to the lesion. Unilateral removal of the superior colliculus alone had only small effects on visual responses in STP. Receptive-field size and visual response strength were slightly reduced in the hemifield contralateral to the collicular lesion. As in the intact monkey, selectivity for stimulus motion or form were similar in the two visual hemifields. We conclude that both striate cortex and the superior colliculus contribute to the visual responses of STP neurons. Striate cortex is crucial for the movement and stimulus specificity of neurons in STP.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Central Visual Field Defects in Patients with Distinct Glaucomatous Optic Disc Phenotypes

2021 ◽  
Vol 223 ◽  
pp. 229-240
Author(s):  
Eren Ekici ◽  
Sasan Moghimi ◽  
Huiyuan Hou ◽  
James Proudfoot ◽  
Linda M. Zangwill ◽  
...  
Keyword(s):  
Visual Field ◽  
Optic Disc ◽  
Visual Field Defects ◽  
Central Visual Field ◽  
Field Defects

scholarly journals Acute Zonal Occult Outer Retinopathy: Vision Loss in an Active Duty Soldier

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Courtney M. Crawford ◽  
Bruce A. Rivers ◽  
Mark Nelson
Keyword(s):  
Visual Field ◽  
Visual Field Defect ◽  
Vision Loss ◽  
Fundus Autofluorescence ◽  
Final Diagnosis ◽  
Active Duty ◽  
Visual Field Defects ◽  
Fundus Photographs ◽  
Optical Coherence Tomograph ◽  
Field Defect

Objective. To describe a case of acute zonal occult outer retinopathy (AZOOR) in an active duty patient.Methods. In this paper we studied fundus photographs, optical coherence tomograph, Humphrey visual field 30-2, fundus autofluorescence images, fluorescein angiograms, and electroretinography.Results. Exam findings on presentation: a 34-year-old American Indian female presented with bilateral photopsias, early RPE irregularity, and an early temporal visual field defect. Progression RPE damage and visual field defect along with ERG findings support final diagnosis of AZOOR.Conclusion. AZOOR may initially be identified as a broader category of disease called the “AZOOR complex of disorders”. Specific visual field defects, ERG results, and clinical exam findings will help distinguish AZOOR from other similar disorders.

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