Arrangement of ocular dominance columns in human visual cortex.

The arrangement of the ocular dominance columns in the human primary visual cortex was studied by examining cytochrome oxidase activity in autopsy specimens of occipital lobes obtained from two patients who became blind in one eye before death. By artificially flattening the cortex before processing, it was possible to reconstruct the pattern formed by the ocular dominance columns throughout most of the primary visual cortex. The columns form a mosaic of irregular parallel stripes about 500 microns to 1000 microns wide (right eye column plus left eye column measures 1 to 2 mm), oriented at right angles to the boundary of the primary visual cortex. The columns are wider near the boundary of the primary visual cortex and within the representation of the peripheral visual field, the ocular dominance columns of the ipsilateral eye become fragmented until they disappear altogether at the border of the monocular crescent representation. The arrangement of ocular dominance columns in the human visual cortex is very similar to the pattern reported in the macaque monkey, although the columns in humans are wider.

Attenuating effects of diazepam on the electroretinogram of normal humans.

Response/log I curves were obtained under conditions of dark-and light-adaptation in seven normal male volunteers. For each subject, a baseline electroretinogram (ERG) was recorded. In the same afternoon, a second ERG was obtained after 0.05 mg/kg diazepam, and a third ERG was recorded following 0.10 mg/kg diazepam. Under conditions of dark-adaptation, the following dose-dependent changes were identified: 1) Diazepam attenuated the rod b-wave peak amplitude and increased its implicit time; 2) The dark-adapted longer wavelength cone a-wave and 'blue cone' b-wave showed an increased implicit time; 3) All oscillatory potentials showed an increased implicit time. Under conditions of light-adaptation, dose-dependent decreases in peak amplitude and delays in implicit time were observed for the a- and b-waves. The effects of diazepam on the human ERG were more profound under conditions of light- than dark-adaptation.

Chronic eyelid closure and its effect upon the human cone and rod electroretinogram.

The human rod and cone systems have different spectral and adaptive sensitivities. Ganzfeld electroretinogram responses show that chronic eyelid closure, such as extensive symblepharon, can lead to dark-adaptation of the rods but simultaneously permit light-adaptation of the cones of the same eye. This effect is due to the red-filtering properties of the closed eyelid and the differential sensitivity of the two photoreceptor systems to the long wavelengths.

Mapping of retinal and geniculate neurons onto striate cortex of macaque.

A unity ratio between geniculate and ganglion cells can be shown in the macaque visual system. Comparison of the densities (cells/deg2) in the dorsal lateral geniculate nucleus (dLGN) of parvocellular (P) and magnocellular (M) cells, respectively, representing color-opponent and broad-band ganglion cells, with cortical magnification (mm2/deg2) gives the number of afferents per square millimeter in striate cortex (V1). For P cells, this afferent density rises only slightly with eccentricity, indicating that V1 magnification is approximately proportional to the density of P cells. The density of cytochrome oxidase puffs in V1 also rises only slightly with eccentricity. As a result, the number of P-cell afferents per puff-centered module is remarkably constant throughout V1. Our findings thus support a novel hypothesis of peripheral scaling, in which V1 cortical magnification is based on the mapping of just 1 class of afferent onto V1 modules. This "P-cell module" in V1 may be composed of submodules corresponding anatomically to the honeycomb cell in layer 4A of V1 and physiologically to a minimal complete set of color-opponent ganglion cells. In contrast, the afferent density of M cells rises steeply with eccentricity, so that the reciprocal of their afferent density, the cortical "domain" of M cells, declines with eccentricity. This decline is similar to that of point-image area in V1. As a result, the number of M cells per point-image area is nearly constant. This quantity is analogous to the receptive-field coverage factor in the retina, which for M cells is fairly constant and greater than unity at all eccentricities. The results show fundamental differences between the neural maps of these 2 major cell types, differences that are likely to have psychophysical consequences.

The effect of metoclopramide on the Ganzfeld electroretinogram.

Antecedent light flashes enhance the amplitude of the electroretinogram (ERG) oscillatory potentials, but do not modify other ERG responses nor dark-adaptation sensory thresholds. Metoclopramide infusion (i.v.) has a generally attenuating effect on the ERG, which is more evident under conditions of dark- than light-adaptation. Metoclopramide decreases the peak amplitude of the rod b-wave and the dark-adapted cone b-wave in a similar manner; it also significantly increases the implicit time of the rod b-wave, but not of the dark-adapted cone b-wave. In addition metoclopramide reverses the enhancement of the oscillatory potentials by the antecedent light flashes.

Age and illuminance effects in the Farnsworth-Munsell 100-hue test.

Seventy-five normal volunteers (20-78 yr) were tested on the Farnsworth-Munsell 100-hue test at each of five illuminance levels. Each cap score distribution was analyzed by fitting a two-cycle sine wave whose amplitude and phase characterize the polarity of the error distribution and its axis. Analysis of these parameters reveals a similarity between tritanlike defects in older groups and those of younger groups at lower illuminance levels. These data are also useful for specifying age norms for the polarity of the error distribution.

Clinical measurement of saturation discrimination.

In this paper, we describe how a circular reflective neutral-density wedge can be used to construct an apparatus which provides a relatively rapid procedure for the clinical measurement of saturation discrimination. Subsequent to an initial measurement of the patient's relative luminosity function, the patient need only turn a single control which varies the colorimetric purity of a test field which remains luminance matched to a white light reference field.

Temporary loss of foveal contrast sensitivity associated with panretinal photocoagulation.

Snellen visual acuity and spatial contrast sensitivity measurements were used to monitor changes in foveal vision in two patients undergoing argon laser panretinal photocoagulation (PRP) in both eyes for proliferative diabetic retinopathy. Foveal edema developed in one of the four eyes. The remaining three eyes showed no signs of foveal edema, but developed temporary losses in high spatial frequency contrast sensitivity during the closely spaced PRP treatments. Since Snellen visual acuity remained stable at the prelaser level, these results indicate the need for more sensitive measures of visual resolution to monitor foveal integrity in patients undergoing PRP.

Density profile of blue-sensitive cones along the horizontal meridian of macaque retina.

Intravitreal injection of some fluorescent and nonfluorescent tissue-reactive dyes results in selective intracellular staining of a specific population of cones of macaque retina that have been identified tentatively as blue-sensitive cones. This paper describes quantitative density profiles of these cones as a function of retinal eccentricity. These profiles were measured from 0 deg to about 60 deg eccentricity along the nasal and temporal segments of the horizontal meridian of macaque retina. Stained cones were found to be absent from the very center of the fovea. These cones reach peak densities at 0.75-1.50 deg eccentricity, and decrease with greater eccentricity, more rapidly on the temporal than on the nasal segment of the horizontal meridian. Peak densities were found to be slightly closer to the foveal center of the retinas of adult male than of adult female macaques. Packing patterns of stained and unstained cones are discussed as is the mathematic expression of stained cone distribution. The spatial properties of the retinal distribution of stained cones agree very closely with those obtained in psychophysical human studies and other anatomic simian studies of blue-sensitive cones.

Gyrate atrophy of the choroid and retina. Early findings.

Examination of two sisters ages 2 years 10 months and 6 years four months with gyrate atrophy of the choroid and retina provided an opportunity for detailed clinical investigation. Although the chorioretinal lesions were confined to the peripheral retina in the older case and were quite minimal in the younger case, there was electroretinographic evidence of marked involvement of the cone and rod systems. These cases offer an opportunity to assess an arginine restricted diet in preventing the progress of the disease.

Spatial contrast sensitivity. Importance of controlling the patient's visibility criterion.

Clinical spatial contrast sensitivity measurements are typically made using psychophysical methods that do not specify the response criterion being used by the patient in judging grating visibility. Results of this report show the necessity of such methods for (1) maximizing detectability of early contrast sensitivity deficits by minimizing normal sample variance, and (2) ensuring that changes in an individual's contrast sensitivity reflect changes in vision and not simply fluctuations in the patient's criterion for judging grating visibility.

Non-fluorescent dye staining of primate blue cones.

The intravitreal injection in macaque retina of the fluorescent dye Procion yellow can selectively label a specific cone population whose eccentricity distribution and angular separation are consistent with those of the blue-sensitive cones of human and non-human primate retinas. Because at the concentrations used the dye is poorly visible in conventional light microscopy, fluorescence microscopy is required for the observation of the stained cones. In this paper we describe several alternative methods for the staining of blue cones in primate retina, staining that can be visualized in conventional light microscopy and, with some methods, electron microscopy.

Effect of artificial central scotoma on the spatial contrast sensitivity of normal subjects.

Spatial contrast sensitivity was measured in normal subjects with and without a retinally stabilized artificial scotoma (either circular or rectangular), which precluded foveal vision. Our results indicate that the type of contrast sensitivity loss obtained (predominantly high frequency or overall) depended on temporal factors associated with grating presentation. A predominantly high frequency loss was obtained when grating contrast was turned on and off gradually. An additional low frequency difference was obtained when grating contrast was turned on and off abruptly.

Is there a high concentration of color-selective cells in area V4 of monkey visual cortex?

1. Recordings were made from neurons located within the central-field representation of the V4 area of extrastriate visual cortex using a semichronic, nitrous-oxide preparation; the properties of 174 cells were examined in sufficient detail to permit their classification. Cyto- and myeloarchitectural studies confirmed the identification of the area. 2. Color-selective cells with either color-biased or color-opponent properties represented about 20% of the examined population. Their incidence was not significantly different from that of similar cells encountered in penetrations into the central-field representation of area V2. 3. Most color-selective cells had color-biased properties, responding best to wave-lengths shorter than 460 nm, or longer than 580 n, or both. No examples of "green-biased" cells were found. Some color-biased cells responded to photopically matched white light, while others did not. Very few cells showed overt color-opponent responses. The spectral sensitivity of color-selective cells was not unusually narrow. 4. Cells lacking color selectivity and responding equally well to chromatic and achromatic lights of equal photopic luminosity, were the most commonly encountered cell type in penetrations of different parts of the V4 area (56%). Other than color, these cells showed stimulus preferences like those of color-selective cells. 5. One-fourth of V4 cells could not be systematically driven with the various stimuli used. This finding is consistent with recent results of recordings from the prelunate gyrus of the behaving monkey suggesting that some V4 cells receive extraretinal signals. 6. Our results do not support recent claims that V4 is specialized in the detailed analysis of color information.

Spectral bandwidths of color-opponent cells of geniculocortical pathway of macaque monkeys.

1. The spectral-response bandwidth and peak sensitivity of the responses of color-opponent retinal ganglion cells of the macaque monkey were examined in conditions of neutral adaptation. Color-opponent cells showed specific "signatures" in plots of response bandwidth versus wavelength of the peak sensitivity that allow for an acceptable estimate of the cone types whose signals mediate cell responses. 2. Averaged spectral bandwidths of color-opponent ganglion cells were compared with published data from color-selective neurons of subsequent levels of the geniculocortical pathway, including the extrastriate area termed V4. No significant differences were found between color-selective cells of the retina, dorsal lateral geniculate body, striate cortex, and V4. 3. The spectral location of the peak sensitivity of responses of the various types of color-opponent ganglion cells showed a relatively broad distribution, loosely clustering at some spectral loci. Comparison of such distribution with that of recently reported V4 cells response indicates that a remarkable scarcity of "blue/yellow" opponent responses in such reports. 4. In association with more recent electrophysiological studies of V4 cells, the results do not support current claims of a color specialization of this extrastriate area, and suggest lack of significant spectral tuning of the retinal output in, so far known, higher visual centers having color-selective cells.

S-antigen uveitis in primates. A new model for human disease.

Uveitis was induced rhesus monkeys immunized with purified retinal S-antigen. Focal retinal and subretinal infiltration, in addition to periphlebitic changes, were observed histologically. Immunized monkeys had similar cell-mediated in vitro immune responses to the S-antigen as do humans with posterior uveitis. Circulating immune complexes at the time of disease could not be detected. This primate model supports the notion that the S-antigen may play a role in human uveitis.

Gyrate atrophy of the choroid and retina: improved visual function following reduction of plasma ornithine by diet.

In a patient with gyrate atrophy of the choroid and retina, an arginine-deficient diet has reduced plasma ornithine concentration fivefold during the past 20 months. Subjective improvement in her visual function was noted approximately 15 months after institution of her diet. This has been documented by improvements in the electroretinogram, dark-adaptation, and color vision. The improvement involves rod and, to a lesser extent, cone function. The results, although preliminary and limited to a single patient, suggest that reduction of plasma ornithine with a low arginine diet is beneficial in this disease.

Protan-like spectral sensitivity of foveal Y ganglion cells of the retina of macaque monkeys.

1. The spectral sensitivity of two varieties of macaque Y ganglion cells with a centre-surround organization, type III (non-colour opponent) and type IV (broad-band colour opponent), was examined with test stimuli of different size, shape and wave-length. 2. The spectral sensitivity of type III cells to large stimuli decreased at the long wave-lengths with decreasing retinal eccentricity; this change was due to a lower sensitivity of green-sensitive than of red-sensitive cone input to the surround of foveal cells, which resulted in stronger surround antagonism at the long than at the short wave-lengths leading to a rudimentary form of colour opponency. 3. The spectral properties of foveal type III cells were intermediate between those of perifoveal type III cells, whose surrounds receive a rather similar input from both cone types, and of the predominantly foveal type IV cells, whose surrounds appeared to lack input from green-sensitive cones. 4. The results indicate that both cell types represent varieties within a continuum of a single macaque Y-cell system which has a reduced long-wave-length sensitivity in the foveal region. The fact that a similar reduction of long-wave-length sensitivity can be observed in (foveal) macaque photopic luminosity functions measured with different techniques by different authors suggest that both types of Y cell have an important role in the processing of luminance information.