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PubMed1989

Effect of early visual pattern deprivation on development and laminar distribution of cholinergic markers in rat visual cortex.

In order to evaluate the role of cholinergic cortical mechanisms in the shaping of visual cortical plasticity in more detail the present paper summarizes recent studies on the laminar distribution of muscarinic acetylcholine receptors, choline acetyltransferase, and sodium-dependent high-affinity choline uptake sites during postnatal ontogenesis of the visual cortex of monocularly derived rats using autoradiographic techniques as well as quantitative biochemical methods after separating the different cortical layers by a cryocut technique. The data are correlated to the laminar distribution of cholinergic fibers within the visual cortex as studied by the immunohistochemical visualization of choline acetyltransferase. The laminar distribution of cholinergic receptor binding in the visual cortex changes during ontogenesis. In adult rats, the highest muscarinic acetylcholine receptor density is found in layer I. The activity of the choline acetyltransferase is rather uniformly distributed in all cortical layers. Adult activity values are reached at the age of 25 days. In adult rats the enzyme activity is highest in layer V. In all visual cortical layers the highest 3H-hemicholinium-3 binding to choline uptake sites during the postnatal period studied is already detectable at the age of 10 days, then binding decreases sharply until day 25 at which age it nearly equals the value found in the adult brain. Binding sites exhibit highest density in layers I and IV of the adult rat visual cortex. Monocular deprivation resulted in significant changes in all three parameters studied with different cortical laminae preferentially affected. The data suggest that the normal laminar development of the modulatory function of cholinergic transmission in the rat visual cortex depends on the presence of physiological light stimulation.

Aging↗

PubMed1986

Visual properties and spatial distribution of neurones in the visual association area on the prelunate gyrus of the awake monkey.

We have analysed, in the awake monkey (Macaca sylvana) the functional properties of 489 neurones in the prelunate visual area (PVA, largely corresponding to V4). PVA has a coarse retinotopic organization with the lower quadrant of the visual field represented along the prelunate gyrus. The visual periphery is located medio-dorsally, the central visual field laterally near (and within?) the inferior occipital sulcus and the upper quadrant latero-ventrally. The vertical meridian runs caudally within the lunate sulcus, the horizontal meridian crosses the prelunate gyrus and continues into the superior temporal sulcus. Receptive field diameters of neurones vary between 1 degree and 10 degrees with increase towards the visual periphery, but are strictly confined to the contralateral visual field. 28% of the neurones showed spectral sensitivity. About half of these cells had strong spectral opponency, the other half showed only weak opponency with broader spectral response curves. 11 cells (2%) showed striking centre/surround interactions with inhibition, disinhibition or occlusion of the two mechanisms, and different spectral response ranges of the centre and the surround, respectively. 43% of the prelunate cells were responsive to various spatial features without spectral sensitivity. We distinguished on- and off-center cells (2%), direction and movement sensitive cells (10%) and cells sensitive to gratings of parallel lines within a limited range of orientations (about 10%). A special group were cells which responded strongly to stimuli which contained many contrasts (textures without specific orientations and without regular spatial arrangements) (9%). Many of these cells were specifically responsive to variations of the internal structure of such stimuli. 3% of the cells were strongly activated in connection with behaviour: 11 neurones discharged strongly when the monkey looked attentively at a human face or when he responded with facial expressions to a threatening expression of a person. Photographs of faces were not effective. Some neurones (1%) were activated in connection with eye movement. These neurones were found in the lateral part of the prelunate gyrus. Neurones with spectral or non-spectral properties were clustered within small, irregularly shaped patches of 1-4 mm diameter. It is concluded that the prelunate visual cortex, which we consider as part of area 19, is not just a "colour area", but represents various features of the visual environment (including colour, luminance, movement, texture and behavioral significance), and relates them - through its subcortical and cortical outputs - to behaviour.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1989

Changing patterns of binocular visual connections in the intertectal system during development of the frog, Xenopus laevis. II. Abnormalities following early visual deprivation.

During normal metamorphic and post-metamorphic growth of the frog, Xenopus laevis, there is a major and orderly remodelling of the pattern of neuronal connections in the intertectal system. These changes preserve the spatial registration of binocular visual inputs to each optic tectum in the face of continuous changes in relative eye alignment (Grant and Keating 1989). We suggested that visual experience might be utilised by the intertectal system to effect the maturational remodelling of its connections, with particular involvement in maintaining binocular visual registration. To investigate this suggestion we studied the development of the intertectal system in animals that had been reared in total darkness from before the onset of function in the system. Visual deprivation did not affect the developmental ocular migration that normally occurs in Xenopus, nor did it affect the maturation of the contralateral visuotectal projection. Abnormalities were, however, observed in the ipsilateral visuotectal projection of all dark-reared animals studied, reflecting perturbation of the underlying intertectal system. The abnormalities included disorder and deficits in the projection, which became more marked with age. Quantitative analyses of the spatial registration of binocular visual inputs to the optic tectum revealed that, in all dark-reared animals studied, registration was both significantly poorer and systematically shifted compared to normal controls. Analysis of maturational changes in the pattern of intertectal connections in visually-deprived animals led to the conclusion that intrinsic developmental processes generate an initially well-organised intertectal system and programme much of its continuous expansion with age. Visual experience, however, is necessary for the large scale and orderly remodelling of the system which, during normal maturation, preserves binocular visual registration despite changes in interocular alignment.

Action Potentials↗

PubMed1988

Stability of visual acuity in amblyopic patients after visual maturity.

One hundred thirty patients with strabismic amblyopia who underwent full-time occlusion therapy (FTO) and were followed through to at least 9 years of age were evaluated to determine the stability of visual acuity after visual maturity (after 9 years of age). Of these 130 patients, 89 are included in this review. At the conclusion of the FTO therapy, 92% (82/89) had attained a visual acuity of 20/40 or better, 6% (5/89) had attained 20/50-20/100, and 2% (2/89) remained at 20/200 or less. Of the nine patients in this series in whom patching was initiated between the ages of 6 and 9 years of age, a good visual result was seen in 89% (8/9), with 63% (5/8) of those attaining 20/20 vision. The final visual acuity in this group of patients was taken at an average patient age of 15.9 years. In 75% of the patients (67/89) there was no change in visual acuity over time, while 17% (15/89) showed a one- or two-line decrease, and in 8% (7/89) vision dropped more than two lines. Of those patients who had greater than or equal to 20/40, 88% (56/64) who had a posttreatment visual acuity of 20/20 showed no change at the final evaluation, but only 50% (9/18) of those whose posttreatment vision was between 20/25 and 20/40 were stable. In those patients who needed part-time occlusion (PTO) to maintain equal visual acuity, their stability appeared to be the same as the vision of those whose vision was maintained without PTO.

Adolescent↗

PubMed1995

Study on the primary visual cortex of visually impaired subjects by means of 123I-IMP SPECT and MRI.

We conducted a study of rCBF in the primary visual cortex of visually impaired subjects who have not been subjected to external stimulation for a long period, by means of 123I-IMP SPECT and MRI. The four subjects had lost their sight due to brain tumors (n = 2), glaucoma (n = 1) and trauma (n = 1). 123I-IMP SPECT showed no differences between the visually impaired group and a visually sound control group on visual analysis as well as semiquantitative analysis. MRI of the visually impaired subjects showed no organic changes, such as atrophy, in the occipital cortex. In conclusion, visually impaired subjects have no decrease in rCBF and no anatomical changes in the primary visual cortex.

Adult↗

PubMed1985

Visual agnosia contrasted with visual-verbal disconnection.

Serial neuropsychological findings are contrasted in two cases: one with a syndrome of visual agnosia, the other with a disorder resulting from visual-verbal disconnection. Both patients were impaired in confrontation naming of objects and pictures, but the patient with visual-verbal disconnection was able to perform tasks of color-object matching and pantomime recognition, whereas the patient with visual agnosia could not do so, demonstrating a failure to establish meaningful nonverbal visual-visual association. Additionally, the performance of the patient with visual agnosia reflected an evolution from the apperceptive to associative forms of the disorder, suggesting that the various impairments of visual identification form a continuum of related disorders.

Agnosia↗

PubMed1989

Visually perceived eye level and perceived elevation of objects: linearly additive influences from visual field pitch and from gravity.

Observing a pitched visual field (i.e. tilted around a horizontal axis in the observer's frontal plane) results in large changes in the elevation visually perceived to correspond to eye level (VPEL) and in the perceived elevation and size of stationary objects viewed against the field. With topforward pitch (top toward observer) VPEL lies above true eye level and objects appear smaller and lower; with topbackward pitch VPEL lies below true eye level and objects appear larger and higher. Oscillation of the pitched field induces synchronous perceived oscillation of elevation of a stationary target viewed against the field. Typical VPEL settings deviated from true eye level by 20 degrees with the field pitched at 40 degrees, although some individuals mislocalized by as much as 40 degrees. VPEL varied linearly with visual field pitch with individual slopes for the relation between VPEL and visual field pitch ranging from +0.42 to +0.78 (avg = +0.56). The linear correlation (r) between VPEL in darkness and against an erect visual field was +0.91. The two relations--VPEL vs visual field pitch, VPEL in darkness vs VPEL in the erect illuminated visual field (slope approximately equal to 0.5)--are both accurately predicted by the linear model: VPEL = kvV + kbB; in which V is the influence of visual field structure and B is the influence of the body-referenced mechanism which combines information regarding the orientation of the head relative to gravity, the position of the eye in the orbit, and the vertical location of the image on the retina; kv and kb are the relative weights of V and B with kv + kb = 1. In an illuminated field kv = kb approximately equal to 0.5; in the dark kv = 0, kb = 1.

Gravitation↗

PubMed1995

Visual acuity in a population aged 70 years or older; prevalence and causes of visual impairment.

Visual acuity and the prevalence and causes of impaired vision were studied in an epidemiological cross-sectional population study of inhabitants aged 70 years or older in three communities in the county of Oulu, Finland. 500 of the 560 eligible persons (89.3%) were examined. Information on visual acuity was obtained for 476 co-operative persons (85.0%). 59.0% had a visual acuity of 0.3-0.6 in the better eye. 10.1% (48 persons) had low vision and 1.9% (9 persons) were blind as categorized according to the classification of visual impairment by the World Health Organization. Experienced visual capacity did not, however, always correspond to objective tests. Age-related maculopathy and cataract were the leading causes of visual deterioration. Age-related maculopathy was the main cause of low vision and blindness in 4.6% of the population. In 1.3% the etiology was cataract, and in 2.1% both early age-related maculopathy and cataract were present without obvious dominance. Cataract was often associated with other conditions. Glaucoma was considered the main cause of visual deterioration in 1.5%, diabetic maculopathy in 0.6% and macula pucker in 0.4%. In 1.5% the visual deterioration was due to other causes.

Aged↗

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↗

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↗

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↗

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↗