Yuzo M. Chino

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

SummaryThe 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.

Effects of convergent strabismus on spatio-temporal response properties of neurons in cat area 18

SummarySingle-cell recording experiments were carried out to determine whether rearing kittens with surgically induced convergent strabismus (esotropia) alters the development of receptive field (RF) properties of neurons in area 18. In agreement with previous work on kittens with divergent strabismus (exotropia), there was a marked loss of binocularly driven cells in area 18 of esotropic cats. In contrast to the striate cortex of strabismic cats, the spatial properties of area 18 neurons, including receptive-field size and spatial frequency tuning, did not differ from those in normal controls. On the other hand, we found that contrast thresholds, measured at an optimal spatial frequency, were significantly elevated, and that the contrast gain in many cells was reduced in strabismic cats. These deficits were observed in both eyes, though the cells dominated by the deviating eye had a lower response amplitude at all contrasts. Furthermore, temporal frequency tuning curves were abnormal in strabismic cats in that the optimal frequencies and temporal resolutions were shifted to lower values. These effects were also bilateral. Velocity tuning, measured with a high-contrast bar stimulus, revealed that area 18 neurons in strabismic cats were unable to respond to very high velocities compared to normals. This reduced response was more severe when measured with the deviating eye in spite of the bilateral nature of the deficit. Finally, latencies to electrical stimulation of the optic chiasm or the optic radiation were significantly longer in strabismic cats. The magnitude of these effects was virtually the same for both eyes. From these observations, we conclude that the temporal properties of area 18 neurons, particularly the cells abilities to follow fast temporal modulations, are affected by raising kittens with surgically induced convergent strabismus.

Dopaminergic amacrine cells in the retina of Japanese dace.

The morphological and physiological identification of the cells in the inner retina of Japanese dace was made by means of intracellular single cell recording and dye injection techniques. Our flat mounts and physiological classification revealed that 97 out of 102 sample cells were amacrine cells except for 3 transient neurons possibly being ganglion cells. Only two cells were identified as interplexiform cells. The double-labeling histochemical technique showed that 17 cells including the two interplexiform cells are dopaminergic neurons. Therefore, 15 of 97 amacrine cells in dace retina were dopaminergic cells, a finding which is different from the previously published data.

Properties of X- and Y-type retinal ganglion cells in Siamese cats

There is ample evidence that the visual system of the Siamese cat is different from common cats. These abnormalities suggest possible retinal origins, although no documentation exists. In the present study, single unit recordings were made from 91 misrouted and 209 normally-routed optic tract fibers in Siamese cats. Electrophysiological responses of the misrouted fibers did not differ from those found in the normally-routed fibers of the Siamese cat with the exception of depressed responses to contrast reversal stimuli. X/Y classification of units and experiments on receptive field center sizes, intensity-response functions, and responses to flicker failed to demonstrate significant differences between the misrouted and normally-routed fibers in Siamese cats. These results were not affected by different degrees of interocular misalignment exhibited by the Siamese cat studied. Response properties of retinal ganglion cells in Siamese cats, however, were found to be quite abnormal when compared with common cats. Only 14% (42/300) of all units studied were Y-cells in Siamese cats in comparison to 35% (60/170) in common cats. The percentage of Y-units also was correlated with the severity of interocular misalignment in Siamese cats, i.e. the greater the misalignment of the eyes, the lower the percentage of Y-cells. Experiments on response to contrast reversal stimuli, intensity-response functions and responses to flicker revealed that the ganglion cells in Siamese cats are not as responsive as those in common cats.

Rod and cone contributions to the delayed response of the on-off ganglion cell in the frog

Abstract Delayed responses from on-off ganglion cells were further studied. Spectral sensitivity experiments indicate that signals from cones as well as rods contribute to the delayed response. Chromatic pre-adaptation studies showed that a reduction in the sensitivity of rods results in a smaller amplitude of the late response and a slight increase in delay time, while desensitizing the cone system causes a shorter delay time and a greater amplitude in the late response. These results suggest that rod signals are excitatory and cone signals inhibitory and that these signals summate to elicit the delayed response.

Spectral opponency of on-type ganglion cells and the blue preference of Rana pipiens.

Spectrally opponent processes of ON-type retinal ganglion cells and the blue preference behavior were identified by parallel physiological and behavioral experiments in Rana pipiens. Spectral opponency of retinal ON-units was measured by recording from optic nerve terminals in the anterior thalamus, while the retina was stimulated by combinations of monochromatic stimuli. Spectral opponency of the blue preference was determined in a Y-maze, using similar combinations of monochromatic stimuli. The opponent processes of the ON-units and blue preference are similar in the spectral ranges of excitatory and inhibitory effects. In both cases the spectral opponency can be described as short wavelength excitation and long wavelength inhibition. The data suggest that the short wavelength excitation is based, at least in part, on the green rod (P432) channel, while the long wavelength inhibition is caused, at least in part, by stimulation of the principal and/or single cone (P580) channel. A model is presented to show how receptor interactions may encode this spectrally opponent process. The results support the hypothesis that the blue preference is dependent on information supplied to the anterior thalamus by ON-type retinal ganglion cells.

The time course of inhibition during the delayed response of the on-off ganglion cell in the frog

Abstract Delayed responses of the on-off ganglion cell were studied in the frog optic tectum by single unit techniques. The time course of the long-lasting inhibition during the silent period was examined in detail. It was found that inhibition is strongest at the earliest time measurable (0.5 sec after an early response), and that recovery from inhibition is rapid at the beginning, but it becomes much slower for the rest of the silent period. Furthermore, a brighter stimulus elicits not only a longer silent period, but also stronger inhibition at a given time during the silent period.

Spatial frequency tuning and contrast threshold of striate neurons in Siamese cats

SummaryThe spatial frequency tuning and the contrast-response function of striate neurons in Siamese cats were investigated with drifting sinusoidal gratings of high contrast, and the results were compared to the data obtained in normally pigmented cats. The optimal spatial frequency of the tuning curves obtained from Siamese cats was shifted toward lower values, and the mean optimal spatial frequency was significantly lower as compared to that measured in normal controls. Furthermore, the spatial resolution was severely reduced in Siamese cats, and many tuning curves in these animals showed unusually broad band width. The contrast response functions are characterized by higher contrast thresholds and shallower slopes in experimental animals. The units in Siamese cats had much larger receptive fields. Finally, these abnormalities were found in both simple and complex striate neurons. The present findings are discussed in terms of anomalies in pre-cortical visual neurons and their possible relation to the visual behavior of Siamese cats.

Response properties of X and Y LGN neurons in Siamese cats

SummaryWe investigated quantitatively the receptive-field properties of neurons in the lateral geniculate nucleus of Siamese cats. The experimental animals, “Mid-western” Siamese cats, exhibited varied degrees of ocular misalignment. The percentage of Y-cells, which receive projections from the area centralis, was significantly greater in Siamese cats than in normally pigmented cats. The spatial resolution of many, but not all, X-cells within the central 5 degrees of Siamese cats was reduced. A substantial number of Y-cells had significantly longer latencies to stimulation of the optic chiasm. In addition, some Siamese cat units had abnormal contrast threshold and lineweighting functions along with large receptive field center size and weak inhibitory effects from the RF surround. Finally, large variability was found with respect to the abnormalities among cells within a given cat and more importantly among the individual Siamese cats which we studied.

Abnormal responses of retinal ganglion cells in Siamese cats to moving stimuli

SummaryThe responses of X and Y-Type retinal ganglion cells in Siamese cats to moving slits were compared to those in common cats, in order to assess the center/surround interactions in Siamese cat receptive fields. Responses in the latter animal were quantitatively lower than those in common cats, the RF centers were larger, and the encounter rate for Y-type optic tract fibers was significantly lower than in common cats. Whereas response enhancement of common cat units was predictable following masking of the surround, such an effect could only be observed in Siamese cats when the contrast between the stimulus and background was increased considerably. These data suggest anomalous center/surround interactions in Siamese cats, probably due to the presence of weaker surround influences in that animal.