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PubMed1977

Effect of selective visual interference on visualization.

The extent of visual processing involved in visualizing objects was investigated by the use of selective visual interference. Subjects read concrete words and visualized them. This produced an approximately ten-fold increase in the slope of the latencies of wholistic visualization as a function of set size compared to that when subjects responded after listening to the descriptions of the objects. Males produced significantly steeper slopes than females in both listening and reading conditions, indicating that they find visualization more difficult. It is concluded that the interference on the visualization task was in the main disrupting active visual processing as no spatial manipulation of the objects was required.

Auditory Perception↗

PubMed1981

Layer-specific labelling of cat visual cortex after stimulation with visual noise: a [3H]2-deoxy-d-glucose study.

Tritiated 2-deoxy-D-glucose (2-DG) was used to demonstrate layer specific uptake of 2-DG at the cellular level in the visual cortex of the cat after stimulation with different kinds of visual stimuli. Two-dimensional static Gaussian visual noise drifting across the visual field led to an increased accumulation of 2-DG in layers III and V as compared to the amount of radioactivity in layer IV. In unstimulated control tissue of visual cortex a homogeneous pattern of labelling was found. Horizontal bars moving vertically across the visual field increased the uptake in layer IV more than in all other layers. Analysis of the 2-DG uptake at the cellular level revealed that visual noise activated two bands of cells, one above and one below layer IV, whereas bar stimuli activated cells mainly in layer IV. Accumulation of 2-DG was always higher in the perikarya than in the surrounding neuropil. These results confirm the physiologically recorded properties of cells in different cortical layers.

Animals↗

PubMed1994

Visual hemispheric dominance induced in split brain cats during development: a model of deficient interhemispheric transfer derived from physiological evidence in single visual cortex cells.

The effects of cancellation of both interhemispheric callosal transfer and interocular interactions, were studied in early monocularly deprived cats. The main purpose of this study was therefore to prove whether unilateral hemispheric dominance would result under these conditions and to what extent each hemisphere will be functionally independent. Secondly, we have attempted to establish such an experimental model physiologically, on the single cell level. Interhemispheric transfer was surgically canceled by sagittal transection of the corpus callosum. In addition, the ocular projections were separated by sagittal transection of the optic chiasm in the transbuccal approach. This condition had practically induced visual split brain condition in these cats. These manipulations were carried out concurrently with monocular deprivation (SBDK group) which was surgically done by eye closure during the critical period of development of the visual system. Thus, the hemisphere ipsilaterally to the visually deprived eye had developed under conditions of deficient visual experience while the hemisphere ipsilaterally to the normal eye had developed under conditions of unaltered visual experience. A group of cats (SBK) similarly operated but equally binocularly exposed during development was served as controls. In addition, adult cats similarly operated during adulthood either chronically or acutely were studied to evaluate the effects of interhemispheric and interocular separation. Other groups of cats were also studied for comparison, and included sham operated and normal adult cats. At adulthood, electrophysiological studies were done on these cats, in which action potentials were extracellularly recorded from single cells in the visual cortex (area 17-18 boundary) following anesthesia and paralysis. Stimulation was carried out manually and by a computer driven optical system, presenting on a tangent screen light bars at various spatial positions, orientations and directions. Receptive fields were thus mapped for all neurons and their dimensions and eccentricities were measured. The responsiveness, ocular dominance and other parameters were also studied for these cells. The results in the early deprived cats and in their controls, had shown a full separation between the two hemispheres, as reflected in the almost absolute ipsilateral eye responsiveness (> 97.0% cells). In comparison, in the sham operated and in the normal control cats only minor proportions of cells (13.0-18.7%) have been found as ipsilaterally and monocularly driven, showing almost full interhemispheric and interocular interaction. The main difference, however, in the results between the early monocularly deprived cats and their controls is that in the first group the two hemispheres were asymmetric concerning the amount of visual activation and in the second one they were very symmetric.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1975

Responses to visual stimulation and relationship between visual, auditory, and somatosensory inputs in mouse superior colliculus.

The superior colliculus was studied in anesthetized mice by recording from single cells and from unit clusters. The topographic representation of the visual filed was similar to what has been found in other mammals, with the temporal part of the contralateral visual field projecting posteriorly and the inferior visual field projecting laterally. At the anterior margin of the tectum receptive fields recorded through the contralateral eye and invaded the ipsilateral visual hemifield for up to 35 degrees, suggesting that the entire visual field through one eye is represented on the contralateral superior colliculus. Cells located closest to the tectal surface had relatively small receptive fields, averaging 9 degrees in center diameter; field sizes increased steadily with depth. The prevailing cell type in the stratum zonal and superficial gray responded best to a small dark or light object of any shape moved slowly through the receptive-field center or to turning a small stationary spot on or off. Large objects or diffuse light were usually much less effective. Less than one-quarter of superficial layer cells showed directional selectivity to a moving object, the majority of these favoring up and nasal movement. The chief visual cell type in the stratum opticum and upper part of the intermediate gray resembled in the newness neurons described for many other vertebrates: they had large receptive fields and responded best to up and nasal movement of a small dark or light object, whose optimal size was similar to the optimum for upper-layer cells. If the same part of the receptive field was repeatedly stimulated there was a marked tendency to habituate. Only very few cels responded to the ipsilateral eye. Intermixed with visual cells in the upper part of the intermediate gray were cells that responded to somatosensory or auditory stimuli. Here bimodal and trimodal cells were also seen. In deeper layers somatosensory and auditory modalities tended to take over. These two modalities were not segregated into sublayers but rather seemed to be arranged in clusters. Responses to somatosensory and auditory stimuli were brisk, showing little habituation to repeated stimulation.

Acoustic Stimulation↗

PubMed1990

Visually guided behavior of monkeys after early binocular visual deprivation.

Four infant monkeys were binocularly deprived of vision through their first year of life. After the end of the deprivation their visually guided behavior was followed for one year. Behavioral tests were performed to assess their visual functions. The performance of the deprived monkeys was compared with the performance of three normally sighted monkeys. The following functions were tested: the monkey's ability to detect a moving light spot, to track a moving object, to grasp an object, to chatter the teeth in response to a threatening face, to pick pellets from a board, to respond to a sudden visual threat and to move about in a wide space. The visually deprived monkeys remained severely visually handicapped. They were able to detect a moving light spot in a darkened room and to recognize the movement of large objects. However, they continued bumping into objects and used tactile exploration when moving about in a wide space. They never learned to respond to a threatening face, which for a normal monkey is part of the normal behavioral repertoires. The persistently poor visually guided behavior of these monkeys is in agreement with the electrophysiological findings in the posterior parietal association cortex of these monkeys; early visual deprivation permanently reduces the number of visually responsive cell groups in this association area.

Animals↗

PubMed1987

Visual loss in pseudotumor cerebri. Incidence and defects related to visual field strategy.

Visual field examinations were performed serially on 20 patients with pseudotumor cerebri using a modified Armaly-Drance visual field strategy with a Goldmann perimeter as well as an automated perimeter (Octopus). Visual loss was found in 75% of eyes using the manual strategy and in 77.5% of eyes with automated threshold perimetry. This incidence of visual loss is 50% greater than any previously reported series. All major defects detected were present with both types of perimetry. Both strategies were more sensitive for documenting visual loss than previously described strategies. Since therapy for pseudotumor cerebri is determined by the degree and progression of visual loss, a specific sensitive strategy, rather than routine screening perimetry, should be used for determination of visual loss.

Adult↗

PubMed1992

Comparison of preoperative 10-Hz visual evoked potentials to contrast sensitivity and visual acuity after cataract extraction.

Cataract patients whose surgical outcomes were in question were referred for testing by visual evoked potentials, elicited through closed eyelids by a luminance stimulus (flash) that appeared 10 times per second. Visual evoked potentials were rated as normal (predicted acuity of 20/50 or better) or abnormal (predicted acuity of 20/60 or worse). Postoperative Arden and Optronix contrast sensitivities and visual acuities were determined in 37 patients who had no intraoperative or early postoperative complications. Arden grating scores of less than 100 were rated as normal. The optimal and cutoff spatial frequency values were determined for the Optronix scores. Optimal and cutoff values of greater or equal to 1 c/deg and 12 c/deg, respectively, were rated as normal. Visual acuities were considered normal at 20/50 or better. Preoperative visual evoked potentials were quantitatively compared to the postoperative contrast sensitivities and visual acuities by 2 x 2 contingency tables. The accuracy of prediction was 79% for the visual acuities, 62% for the Optronix optimal values, 70% for the Optronix cutoff values and 62% for the Arden gratings.

Aged↗

PubMed1994

Normal visual fields measured with Octopus-Program G1. II. Global visual field indices.

To complement results from individual test locations, clinicians also evaluate indices, as they give a succinct overview of the visual field. This, however, requires exact knowledge of their variability. The present study was designed to determine normal interindividual variability of global visual field indices and incorporates a data base of a multicenter study performed with Octopus 201 perimeters using Program G1. The 824 fields thus obtained included 139 fields of 139 healthy volunteers who had undergone two previous visual fields and completed all three phases of program G1. The index mean sensitivity showed a significant and linear decrease with increasing age, 0.064 dB/year of life. The indices loss variance, corrected loss variance, and short-term fluctuation did not correlate significantly with age. Percentiles are given for these visual field indices. While within the limits of normal values provided by the manufacturer for these indices, these results suggest that visual fields with "borderline" values require further clinical investigation in reliable, experienced subjects. The results may help clinicians to better evaluate global visual field indices and, therefore, to detect loss of visual function earlier.

Adult↗

PubMed1988

Development of the kitten visual cortex depends on the relationship between the plane of eye movements and visual inputs.

1. Previous experiments have demonstrated that eye movements, acting through the extraocular muscle (EOM) proprioceptive afferents, are necessary for the development of orientation selectivity in the cells of the kitten visual cortex. New experiments were carried out to study the effect of the plane of eye movements on the preferred orientation acquired by the visual cortical cells. 2. Dark-reared (DR) kittens were operated on at 5-6 weeks of age. In the first series of experiments, 4 out of the 6 EOMs were removed bilaterally in such a way that both eyes could only move in a single plane, either vertical or horizontal. In the second series of experiments, the same operation was performed on one eye which was also sutured shut and, on the other side, the EOM were deafferented by intracranial section of the ophthalmic branch of Vth nerve and the eye left open. 3. 1-4 days after surgery the kittens were given 6 h of visual experience and 12 h later were prepared for visual cell recording in Area 17. 4. In kittens of the first series: orientation selectivity developed in the majority (60-65%) of visual cells, most of which encoded horizontal orientations when the eyes had moved in the vertical plane and vertical orientations when the eyes had moved in the horizontal plane. These results show that the plane of eye movements during early visual experience influences the distribution of preferred orientations with an orthogonal relation. Ocular dominance histograms were "strabismic like". 5. In kittens of the second series: orientation selectivity developed in 40-50% of cells, about half of which were tuned for the orientation orthogonal to the direction of movement of the occluded eye, as in experiment I. The seeing, deafferented eye, presumably would have sent normal visual inputs centrally, corresponding to displacements on the retina in every direction since the ocular motility of that eye had not been disturbed. However, proprioceptive information about its movements was suppressed. As only some of the EOMs of the occluded eye were still present and connected, the conclusion is that the observed influence of the plane of eye movements acts through the proprioceptive afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1982

Hemiretinal differences in the effect of a rotating visual background on the subjective visual vertical.

Sixteen normal subjects were tested for their accuracy in judging the verticality of a visual edge before or during exposure to a moving visual background. All subjects showed a counter-rotation of the subjective visual vertical as a consequence of movement of the visual background. The effect was stronger for binocular than monocular viewing and for nasal than temporal hemiretina stimulation. No hemispheric asymmetries were observed. These results show a predominance of the crossed visual pathways originating from the nasal hemiretinae in a visual effect presumably involving a visual-vestibular interaction.

Adolescent↗

PubMed1994

Effects of auditory and visual interference on auditory-visual delayed matching to sample in monkeys (Macaca fascicularis).

Two monkeys were trained on an auditory-visual (AV) delayed matching-to-sample (DMS) task with auditory cues serving as sample stimuli and visual cues serving as comparison stimuli. To determine whether the monkeys were remembering auditory or visual information during the delay period, auditory and visual interference were presented following the sample stimulus. Auditory interference had little effect on AV DMS performance. In contrast, visual interference severely impaired AV DMS performance, indicating that the monkeys were remembering visual information during the delay period. This finding may reflect a predisposition of monkeys toward remembering information via their dominant visual modality.

Animals↗

PubMed1992

Visual acuity and visual field development after cryocoagulation in infants with retinopathy of prematurity.

Visual development was studied in 10 very-low-birth-weight infants (less than 1500 g) with retinopathy of prematurity (ROP) stage 3+ who had been treated with cryocoagulation in both eyes. Binocular visual acuity (acuity cards method) and binocular visual fields (kinetic perimetry) were assessed repeatedly in the first year of life. At 12 months corrected age, visual acuity was normal in seven and impaired in three infants, who appeared to be severely myopic. Normal visual fields were found in eight infants at this age. The results indicate that cryotherapy in cases of ROP stage 3+ does not interfere with visual acuity development. The effect on visual field development needs further investigation.

Cryosurgery↗

PubMedDate not supplied

Visual hand display (VHD) as an introductory procedure for measuring vision in infants and young children with visual impairment.

We developed the Visual Hand Display (VHD) to measure vision in visually impaired infants and young children. The VHD is a circular fabric mitten, which is held easily by inserting the hand between the two surfaces. Black-and-white stripes are attached to one surface, 25, 15, 10, 4, and 2 mm per stripe. The VHD acuity is determined by the shortest test distance and the smallest stripes that the patient can detect. The VHD acuities were compared with preferential looking (PL) staircase acuities in 130 patients (53 males, 77 females; age range, 2 to 13 years; median, 21.0 months). Of these, 107 (82.3%) had various degrees of retinopathy of prematurity. The correlation between the VHD and the PL acuities was high (R2 = 0.849). PL acuities were better than the VHD acuities in 98/130 patients (75.4%), with an average difference of 0.51 (SD = 0.70) octave. The visual acuity differences were more pronounced in subjects with slight visual impairment and much less in subjects with severe visual impairment. The VHD seems to be an effective introductory method to evaluate visual acuity in severely visually impaired infants and young children. This method also would be effective with severely mentally and physically disabled patients who cannot undergo PL testing.

Adolescent↗

PubMed1992

The effect of visual experience on development of NMDA receptor synaptic transmission in kitten visual cortex.

We have studied the effect of dark rearing on the development of excitatory amino acid transmission in 6-week-old kittens. In normal kittens, the NMDA component of the visual response decreases between 3 and 6 weeks of age for cells located in layers IV, V, and VI (Fox et al., 1991). Dark rearing to 6 weeks of age prevents this decrease. Subsequent exposure to light allows the decrease to proceed. Ten days in the light after 6 weeks in the dark was sufficient to decrease the NMDA component of the visual response to the same levels seen in light-reared animals of the same age. Comparison of the effect of the non-NMDA antagonist 6-cyano-7-dinitroquinoxaline-2,3-dione with the NMDA antagonist aminophosphonovalerate showed that the changes were due to the relative contributions of NMDA and non-NMDA receptors to the visual response rather than the overall contribution of glutamate receptors. We also studied the receptive field properties of the cells in the various groups of kittens. Cells given 4 d in the light after 6 weeks in the dark showed increased direction selectivity but little change in response firing rate. After 10 d in the light, visual responses did show some recovery toward adult values, but neither average firing rates nor the proportion of direction-selective cells reached the levels found in normal 6-week-old animals, contrary to the suggestion that a short period in the light can reverse the effect of dark rearing completely. These results show that the decrease in the NMDA component of the visual response seen during normal development of the cortex is caused by visual experience. Changes in NMDA receptors and developmental events such as geniculocortical afferent segregation and acquisition of orientation tuning covary as a function of visual experience rather than age, strongly suggesting that NMDA receptors are involved in experience-dependent developmental processes.

2-Amino-5-phosphonovalerate↗

PubMed1991

Flash visual-evoked potentials and flash electroretinography in the preoperative visual prognosis of eyes with cataracts.

This study evaluated the reliability of flash visual-evoked potentials and flash electroretinography in the prognosis of postoperative visual acuity after cataract extraction. We tested 94 patients with cataract in whom the preoperative visual acuity ranged from light perception to 3/10. On the basis of the electrophysiologic tests, we formulated three types of preoperative visual prognosis: high, intermediate, and poor. To assess the postoperative visual acuity, all subjects were followed for at least three months after cataract extraction. Visual acuity was subdivided in three arbitrary classes: less than or equal to 1/10, between 2/10 and 5/10, and between 6/10 and 10/10. Finally, we evaluated the reliability of our preoperative prognosis. Statistical analysis of our results (using the chi-square test) showed our predictions were highly significant for the total sample, revealing a strict correlation between our prognosis and the final visual acuity.

Adult↗

PubMed1990

The predictability of infant visual-evoked response testing on future visual acuity.

We reviewed the records of 27 infants with abnormal eye examinations and visual-evoked response (VER) testing (mean age, 10.5 months) who subsequently underwent a long-term follow-up ophthalmology examination (mean duration, 41 months). The infants were initially diagnosed with various ocular disorders including cortical blindness (eight), optic nerve hypoplasia (six), congenital cataract (two), and retinopathy of prematurity (one). Standard optotype visual-acuity determinations were available in the follow-up records of 11 children (21 eyes), and fixation behavior was obtained in the remaining 16 children (32 eyes). Results revealed that pattern-reversal VER P1 latency was predictive (87%) of whether visual acuity was equal to (or better than) or worse than 20/100 and whether a patient would have good fixation behavior (fix and follow, FF) or poor fixation (no FF) (86%) (P less than .001). Although flash VER P1 latency was also predictive of later visual acuity or good fixation (73%), it was not statistically significant. Pattern VER P1 amplitude and flash VER P1 amplitude were not predictive of later visual function. The predictive power of pattern VER P1 latency for later visual function probably relates to its reflection of macular function and low variability. An analysis of the variability of each of the four VER factors in normal infants (n = 50) indicated that pattern VER P1 latency was the least variable, and consequently most sensitive, VER factor for detecting and quantifying pathology. Overall, the results of this retrospective study suggest that pattern VER P1 latency may have important predictive power for later visual function in infants with an initially abnormal ophthalmologic examination.

Evoked Potentials, Visual↗

PubMed1989

[Visual perception in normal children and adults I. Developmental changes in dominance of visual field in normal children].

Developmental changes of dominance of visual field was evaluated using a tachistoscope in 70 normal subjects from 4 years of age up to adulthood (35 males and 35 females). The time of exposure was measured under two experimental conditions; simultaneous stimulation of different types to both left and right fields, or a single stimulus only to one visual field. One of the following stimuli was exposed to the visual field; one, two or three letters of Japanese characters ("hirakana"), one of Chinese characters ("kanji"), figures, and Roman alphabets. Simultaneous bilateral stimulation revealed frequent dominance in the right visual field, which was established by 4 years of age. The average time of exposure become shorter with age up to 6-7 years for one "hirakana" letter and one "kanji", and up to 10 years for two and three "hirakana" letters. All four left-handed subjects in this study showed dominance of the right visual field. Dominance of the left visual field was observed in 3 of 52 subjects with dominance of the right eye (5.8%), and in 5 of 15 with dominance of the left eye (33.3%). This difference was statistically significant (chi 2 = 8.41, p less than 0.01). It was suggested that dominance of the visual field was related with dominance of the eye, and not with handedness.

Adolescent↗

PubMed1989

[Visual perception in normal children and adults II. Correlation between dominance of visual field and dominance of the eye].

To clarify more precisely about the correlation between the dominance of visual field and dominance of the eye, tachistoscopic examination was performed on 48 normal adults; 24 males and 24 females, and 24 right-handed and 24 left-handed subjects. The mean of the time of exposure was less than 4.5 msec. The time of exposure was independent of handedness, dominance of the eye, sex, or the type of stimulus. Four right-handed and four left-handed subjects showed dominance of the left visual field for the A value, suggesting no correlation between handedness and dominance of the visual field. However, six of those eight subjects were found to have dominance of the left eye for the A value, and all seven subjects with dominance of the left visual field for the D value showed dominance of the left eye (chi 2 = 16.39, p less than 0.001). It was concluded that dominance of the eye was significantly correlated with visual field. It is therefore important to examine dominance of the eye as well as dominance of the visual field for evaluation of cerebral dominance with regard to visual perception.

Adult↗