The position sensitivity of retinal X- and Y-cells in cats

Summary We have devised a measure of a retinal ganglion cell's sensitivity to changes in the spatial position of a grating stimulus. At maximum, this relative position sensitivity is a scaled product of the stimulus spatial frequency and the cell's fundamental component of response to that spatial frequency. We obtained the relative position sensitivity as a function of spatial frequency for 13 X-cells and 14 Y-cells. X-cell functions peak at significantly higher spatial frequencies than do those of Y-cells. At their peaks, X-cells display significantly higher values of relative position sensitivity than do Y-cells. However, Y-cells have higher position sensitivity at lower spatial frequencies, but exhibit less of a range of variation from maximum to minimum than do X-cells. These results are consistent with a hypothesis that Y-cells provide the crucial substrate for form vision at lower spatial frequencies, while X-cells are important for details carried by the higher spatial frequencies.Supported by USPHS grants EY05241 and EY03038     

Adaptation and dynamics in X-cells and Y-cells of the cat retina

Summary On the basis of the spatial summation properties of their receptive fields, cat retinal ganglion cells were classified as either X-cells (linear) or Y-cells (non-linear). Responses were then obtained to a small, centered spot, square-wave modulated in time and superimposed on various levels of diffuse, steady background illumination. When fully dark-adapted, both X-cells and Y-cells produced responses that were entirely sustained. When well lightadapted but still in the scotopic range, both cell types produced largely transient responses with only a very small sustained component. The sustained or transient nature of responses is, therefore, not an invariant characteristic of X-cells and Y-cells in the scotopic range. We also conclude that the mechanism which controls the center's sensitivity in the scotopic range is similar though not identical in the two types of cells.     

Classification of cat retinal ganglion cells into X- and Y-cells with a contrast reversal stimulus

Summary A contrast reversal (alternating phase) stimulus was used to study the responses of 150 retinal ganglion cells from 15 adult cats. Because the majority of the cells did not show perfect linear spatial summation, a ratio of the firing rates at two time periods was used to express the degree of nonlinearity. Y-cells showed a high degree of nonlinearity, and their mean null ratio was significantly lower than that of X-cells. With the stimulus at the null position, X-cells had an unmodulated discharge rate which was significantly higher than maintained activity, while the firing rate of Y-cells was lower than maintained activity. With the stimulus placed at an eccentric position in the receptive field, X-cells responded in a sustained manner, while Y-cells respond transiently. Because of these observations, we conclude that X-cells correspond to the sustained cells, while Y-cells correspond to the transient cells.     

Dark-reared kittens: GABA sensitivity of cells in the visual cortex

Summary Most cells in the visual cortex of dark-reared kittens are unselective for stimulus orientation and we examined the notion that this might be due to insufficiently developed gamma-aminobutyric acid (GABA) receptors. We recorded from cortical neurons and examined their sensitivity to iontophoretically applied GABA. As expected, most units were non-selective for orientation, but application of GABA suppressed impulse activity of these cells just as for orientation selective neurons. This result suggests that the development or maintenance of GABA receptors is not critically dependent on visual experience.On leave from NHK Science and Technical Research Laboratories, Kinuta, Setagaya-ku, Tokyo 157, Japan     

Properties of X- and Y-cells in the rabbit retina

Bevelled glass microelectrodes were used to record spike potentials extracellularly from the ganglion cells of the rabbit retina. Good responses were obtained from the isolated retina or eye-cup preparation for at least 12 hr. Using a contrast reversal stimulus, 63.8% (67/105) of the units showed linear spatial summation (X-cells), and 21.0% (22/105) showed nonlinear spatial summation (Y-cells). The X- and Y-cells in the rabbit retina had physiological properties which were similar to those in cat retina. Directionally selective cells (15.2%) were found to respond poorly, if at all, to the contrast reversal stimulus.     

Two morphologically different types of retinal axon terminals in the rat's dorsal lateral geniculate nucleus and their relationships to the X- and Y-channel

Summary In the rat's dorsal lateral geniculate nucleus (dLGN) two types of retino-geniculate axon terminals have been visualized electron microscopically in adult and juvenile material as well as in Golgi-Kopsch and Golgi-Rapid impregnated sections. The two types differ in size and number of boutons. 2a-terminals have large, sparse boutons, mainly connected with branching zones of geniculo-cortical relay cells (GCR cells). 2b-terminals bear numerous small boutons forming simple contacts with more distal segments of GCR cell dendrites. We are not able to give any information about participation of either type in complex synaptic zones.After horseradish peroxidase (HRP) injection in the superior colliculus optic tract fibres and lateral fibre bundles in the dLGN are labelled with reaction product. Besides these tracts the terminal branching zones of retino-tectal fibre collaterals in the dLGN also show reaction product. As a result of the good visualization of these retinal terminals by the HRP-method they are identified as 2a-terminals. We conclude that 2a-terminals may represent the Y-channel projecting from the retina to both the superior colliculus and the dLGN.Sponsored by a Grant of the Ministry of Science and Technology of the German Democratic Republic     

The effects of monocular deprivation on different neuronal classes in the lateral geniculate nucleus of the cat

Summary Retrograde axonal transport of horseradish peroxidase (HRP) was used to identify two populations of cells in the lateral geniculate nucleus (LGN) of the cat. HRP was injected into area 17 and 18 separately in the same animal, and the neuronal somata giving rise to thalamo-cortical axons, identified by the presence of granular HRP reaction product within them, were measured. The mean size of LGN neurones labelled by injections in area 17 (17-relay cells) was less than of neurones filled from area 18 (18-relay cells). Similar separate injections into area 17 and 18 of monocularly deprived kittens also showed that in non-deprived LGN laminae 17-relay cells were, on average, smaller than 18-relay cells. In deprived laminae, 17-relay cells were some 20% smaller than in nondeprived laminae, but deprived 18-relay cells were 50–60% smaller than normal, being on average, actually smaller than deprived 17-relay cells. We conclude that the population of large LGN neurones projecting to area 18 is more severely affected by monocular deprivation than the smaller neurones projecting to area 17, and discuss the relationship of the morphological results to physiologically defined X and Y cells in the LGN.Preliminary results of this study were presented at the Workshop on Structure of the Nervous System of the European Molecular Biology Organization in Freiburg-im-Breisgrau in April, 1976     

Development of the air righting reflex in cats visually deprived since birth

Summary Classical experiments on the ability of cats to turn in the air during a free fall, the air righting reflex, have shown that vestibular and visual cues can play a role in this behavior. The development of this air righting reflex in kittens blinded since birth has been studied. The results show that the development in the blinded kittens is the same as in normal kittens with vision: mature by 33 days. This result and the comparison with other studies confirm that the air righting reflex is primarily a vestibular controlled reaction.     

Temporal aspects of spatial vision in the cat

Summary Using behavioral techniques, contrast sensitivity for flickering and stationary gratings was measured in ordinary cats. Gratings of low spatial frequency were more easily detected by the cat when temporal modulation was present, but at high spatial frequencies temporal modulation reduced grating visibility. These psychophysical results are consistent with neurophysiological evidence for the existence of two classes of visual cells in the cat, which are distinguishable in terms of their spatio-temporal response properties.     

6-Hydroxydopamine treatment and beta adrenergic receptor binding in kittens

Summary Under some circumstances intraventricular administration of 6-OHDA decreases visual cortical plasticity of kittens; the mechanism for this change is not known, but depletion of norepinephrine (NE) is not the entire explanation. We have examined the effects of 6-OHDA treatment on beta adrenergic receptor binding in kitten visual cortex. Subjects were given vehicle solution alone, a low dose of 6-OHDA which depleted cortical NE without affecting visuocortical plasticity, or a higher dose of 6-OHDA which depleted cortical NE and decreased visuocortical plasticity. Drugs were administered in single daily injections via intraventricular cannulas. Saturation assays were performed on homogenates of visual cortical tissue using ¹²⁵I-pindolol (30–400 pM) along w/isoproterenol (237 M) as a cold competitor. We measured radioactivity bound to tissue and retained on filters and analyzed the data using the EBDA computer program (McPherson 1983, 1985); we determined the affinity constant (Kd) and receptor density (Bmax) in multiple assays for each animal. Despite 75–90% NE depletion in both experimental groups, only the group receiving the lower dose of 6-OHDA showed any evidence of supersensitivity. The Kds did not differ among the groups. The data suggest that the effects of 6-OHDA on visuocortical plasticity are not secondary to beta adrenergic supersensitivity.     

Development of receptive field properties of retinal ganglion cells in kittens raised with a convergent squint

Summary The effects on retinal ganglion cell receptive fields of rearing kittens with convergent squint, surgically induced on the 12th post-natal day, were investigated by utilizing the extracellular single unit recording technique. The data revealed that responses of cross-eyed cat ganglion cells to contrast reversal stimuli were severely depressed and the retinal region exhibiting the best responses varied according to the degree of convergent misalignment of the eyes displayed by each animal. Receptive field sizes of X-type (but not Y-type) units located within 10 ° of the area centralis of cross-eyed cats were significantly larger than those in normally reared cats. Finally, the encounter rate for units exhibiting non-linearity of spatial summation (Y-type) were much lower in cross-eyed cats. The results suggest developmental alterations in the retinal neurophysiology of common cats reared with a large convergent squint.This investigation was supported by NIH grants EY01444 and EY00701     

A comparison of the shift response of X- and Y-cells in the cat's retina

The shift response (McIlwain or peripheral effect) was elicited by either flashing or shifting a grating while the receptive field (RF) was covered by a 30 degree mask in the cat. The responses elicited by shifting the grating was comparable to that elicited by flashing the grating. In 10% of the units, the on- and off-responses elicited by flashing the grating were unequal in amplitude. The larger response corresponded with the light phase which leads to excitation of the surround mechanism of the RF. The maximum firing rates of the shift response did not differ in the different types of units, but the amplitude of the shift response (maximum - maintained firing rates) was significantly larger in Y-cells. For all types of cells, the amplitude of the shift response increased with greater eccentricity of the RF. A strong inhibitory period was found in on-center Y-cells but not in the other types of cells. The latency of the shift response was significantly shorter in Y-cells. The differences in the responses of X- and Y-cells suggest that the lateral pathways used are different for the X- and Y-cells.     

The nature of transcallosal responses in the parietal cortex of kittens

The nature of transcallosal responses in the parietal cortex was studied in experiments with kittens age 2 to 18 days, immobilized with Diplacin. The recorded potentials were represented by a positive-negative complex that was often accompanied by a latent negative oscillation. It was established that the earlier positive-negative oscillation was callosal in nature, and the later, extracallosal. As the kittens developed, we noted that currents responsible for the appearance of early and late negative oscillations converged in time. The results of layer-by-layer analysis of transcallosal responses showed that as the kittens developed, discharge of the surface positive component shifted from layer V to layer III, and discharge of the surface-negative remained at the II–III layer level. The late negative component was recorded only to the level of layers III–IV, having a discharge in layers I–II. Thus, the interhemispheric interrelations in the parietal cortex of kittens are realized by both callosal and extracallosal systems, and an increase in the degree of their interaction can be observed as the kittens grow.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 72, No. 3, pp. 290–298, March, 1986.     

Development of retinofugal neuropil areas in the brain of the alpine newt, Triturus alpestris

Summary The development of the retinofugal projection areas of the brain has been studied in larvae of Triturus alpestris by means of anterograde transported horseradish peroxidase. The optic tract establishes contacts with the optic tectum prior to the onset of robust terminal formation in the diencephalon. The tectum becomes covered by the retinofugal projection in a rostro-caudal direction. The basal optic neuropil develops synchronously with the oculomotor neurons. Their dendrites extend into this neuropil area. A small amount of uncrossed label occurs long before metamorphosis. Around metamorphotic climax this ipsilateral label increases but does not attain the adult pattern even three months postmetamorphosis. The data are compared with the onset of visual induced behaviour.     

Response variability of X- and Y-cells in the dorsal lateral geniculate nucleus of the cat

1. We measured the variability of neural responses in the dorsal lateral geniculate nucleus (dLGN) of the anesthetized, paralyzed cat during repeated visual stimulation with sinusoidal grating patterns. Results are reported for 11 X-cells and 16 Y-cells recorded in laminae A and A1. 2. The responses of most X- and Y-cells varied markedly from trial to trial. The standard deviations of prestimulus, base-line discharge rate. In contrast, the standard deviations of poststimulus responses increased only slightly or not at all with increases in mean discharge rate. 3. Standard deviations of poststimulus responses to optimal stimuli were about one-third the size of mean discharge rates. Relative variability (standard deviation/mean) increased markedly and in nonlinear fashion with decreases in response amplitude, which resulted in considerable overlap of base-line and poststimulus response distributions when stimuli were less than optimal.     

A multicenter investigation with interphase fluorescence in situ hybridization using X- and Y-chromosome probes

Twenty-six laboratories used X and Y chromosome probes and the same procedures to process and examine 15,600 metaphases and 49,400 interphases from Phaseolus vulgaris-leucoagglutinin (PHA)-stimulated lymphocytes. In Part I, each laboratory scored 50 metaphases and 200 interphases from a normal male and a normal female from its own practice. In Part II, each laboratory scored 50 metaphases and 200 interphases on slides prepared by a central laboratory from a normal male and a normal female and three mixtures of cells from the male and female. In Part III, each laboratory scored 50 metaphases (in samples of 5, 10, 15, and 20) and 100 interphases (in samples of 5, 10, 15, 20, and 50) on new, coded slides of the same specimens used in Part II. Metaphases from male specimens were scored as 98–99% XY with no XX cells, and 97–98% of interphases were scored as XY with 0.04% XX cells. Metaphases from female specimens were scored as 96–97% XX with 0.03% XY cells, and 94–96% of interphases were scored as XX with 0.05% XY cells. Considering the data as a model for any probe used with fluorescence in situ hybridization (FISH), a statistical approach assessing the impact of analytical sensitivity on the numbers of observations required to assay for potential mosaicisms and chimerisms is discussed. The workload associated with processing slides and scoring 50 metaphases and 200 interphases using FISH averaged 27.1 and 28.6 minutes, respectively. This study indicates that multiple laboratories can test/develop guidelines for the rapid, efficacious, and cost-effective integration of FISH into clinical service. Am. J. Med. Genet. 76:318–326, 1998. © 1998 Wiley-Liss, Inc.     

The functional development of input-output relationships in the rostral portion of the corpus callosum in the kitten

Summary Microstimulation of the rostral portion of the corpus callosum (CC) was carried out on 21 awake kittens ranging in age from 45 to 105 days to determine the age at which motor responses first appeared and that at which they assumed functional adult-like properties. Motor responses to microstimulation first appeared over an interval ranging from 78–86 days postnatally. As in adults, they consisted of discrete, well-localized contractions of shoulder, whisker, and eyelid muscles according to the stimulated sites. In the first days after their appearance, motor responses differed markedly from those in adults because: (a) they exhibited higher thresholds; (b) they did not faithfully follow pulse trains delivered at 10 s intervals; (c) they had variable and longer latencies. Thereafter, motor responses gradually became stable, faithfully followed suprathreshold stimulation delivered at 0.1/s frequency, and acquired lower thresholds and shorter latencies, until they exhibited adult-like properties at 93–100 days of age. Single-unit recordings were obtained from 138 fibres isolated in the same callosal region submitted to microstimulation in order to study the response properties of the callosal fibres to somatic stimuli in immature animals. On the basis of their reactivity to peripheral stimulation, fibres were classified into three main types: (1) unreactive units (58 fibres), which could not be driven by somatic stimuli. (2) Adult-like units (55 fibres), which were readily driven by somatic stimuli and were endowed with fixed and small receptive fields (RFs) indistinguishable from those of adults. (3) Immature units (25 fibres), which were unsteadily driven by somatic stimuli applied over large areas at the periphery. Neither the RFs nor the adequate stimuli could be reliably determined. This type of units was not found in the adult cat (Spidalieri et al. 1985). The proportion of unreactive units was the highest before the appearance of motor responses and gradually decreased, approaching the adult level after attaining adult-like motor responses. Conversely, the proportion of adult-like units was lowest before the appearance of motor responses and gradually increased, approaching the adult level after motor responses had acquired adult-like properties.     

Comparative development of cell properties in cortical Area 18 of normal and dark-reared kittens

Summary The development of visual cell properties was studied in cortical Area 18 (A18) of normal (NRs) and dark-reared kittens (DRs), from 2 weeks of age to adulthood. In addition to the orientation selective (S) and non-selective (NS) cells, we describe a new type of non-selective cell with a peripheral zone (NSp), which could be either an intermediate form between NS and S cells and included in a sequential model or an immature form of the S cells whose responses are affected by peripheral stimulations. Using accurate coordinates for the area centralis position relative to the optic disc projection as a function of age, we show that: a) the extent of the visual field increases with age in DRs and NRs; b) the retinotopic organization is always present; c) receptive fields, large in the NS cells, reduce to the size of mature S cells as soon as the cells acquire orientation selectivity. This process can occur after only 6 h of visual experience; d) velocity preference shifts toward high velocities, though more so in NRs than in DRs. An interpretation of the development of these properties is proposed, taking into account eye growth, the growth of dendritic fields and the formation of new connections. A comparison with previous results obtained in Area 17 (A17) shows a similar time course of the specification (NRs) and of the despecification (DRs) processes, although the development of A18 is postponed by about 2 weeks. Moreover, the adult-like binocular distribution of ocular dominance depends upon visual experience in A18, while it does not in A17.     

Assessment of contrast sensitivity in kittens after the critical developmental period

Spatial contrast sensitivity was measured in kittens aged 6, 9, and 12 months and in adult cats. Cats had to open one of two small windows, which had a photograph of a grid, in order to obtain food reinforcement. The nonreinforced stimulus was a photograph of a uniform field of the same mean luminance. Visual acuity was constant in kittens aged 6 to 12 months. However, six-month-old kittens had low contrast sensitivity at low spatial frequencies (<0.6 cycles/degree). At the age of nine months, contrast sensitivity over this range increased, though the level seen in adult cats was reached only at the age of 12 months. It is suggested that the increase in contrast sensitivity occurring after the critical developmental period in kittens reflects maturation of higher-order cortical fields involved in the process of recognition. Laboratory of Visual Physiology, I. P. Pavlov Institute of Physiology, 6 Makarov Bank, 199034 St. Petersburg, Russia. Translated from Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 82, No. 10-11, pp. 73–76, October–November, 1996.