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B G Cleland

Publications and source records attributed to B G Cleland.

47 records · Page 3Linked to original sources
PubMed1974

Properties of rarely encountered types of ganglion cells in the cat's retina and an overall classification.

1. In a reference sample of 960 cat retinal ganglion cells, seventy-three had receptive fields departing from the concentric centre-surround pattern.2. Five classes were distinguished among the subset: local edge detectors, direction-selective cells, colour-coded cells, uniformity detectors, edge inhibitory off-centre cells.3. Local edge detectors (forty-five) possessed a radially symmetrical pattern of responses to both centrifugal and centripetal movements of both black and white small targets, an on-off receptive field with a silent inhibitory surround and a low or zero maintained discharge. Their operation could be interpreted as the detection of a contrasting border confined to a small region of the visual field.4. With direction-selective units (eleven) it was possible to find an axis through the receptive field along which sharply different responses could be obtained for opposite directions of movement of small black or white targets.5. Colour units (six) were mostly of the single opponent type having excitatory input from blue-sensitive cones and inhibitory input from long wave-length cones. Both inputs coexisted at the centre of the field and either could be spatially more extensive than the other. One example changed over to rod input under scotopic conditions, another did not.6. Uniformity detectors (five) had a brisk maintained discharge which was reduced or abolished temporarily by all forms of visual stimulation.7. Edge inhibitory off-centre units (three) behaved like uniformity detectors for small targets and fine gratings but like off-centre on-surround units for large targets. Their receptive fields consisted of three concentric regions: a small sized, central edge inhibitory region; a larger zone of off-responsiveness; and an outlying annulus of on-responsiveness.8. It is argued that the above physiological types belong to the morphologically heterogeneous class of cells called gamma cells. The argument is based on similarity in the sizes of receptive fields and dendritic trees and on evidence that the axons are thinner than those of the brisk-sustained and brisk-transient ganglion cells.9. The physiological classification of cat retinal ganglion cells developed in this paper and the preceding one is summarized in a Table.10. It now appears that cat and rabbit possess a qualitatively similar complement of receptive field types among their ganglion cells; the differences reside in the quantitative expression of the various classes.

Animals↗
PubMed1973

Properties of sustained and transient ganglion cells in the cat retina.

1. The functional basis for a sustained/transient classification of cat retinal ganglion cells has been strengthened by quantitative measurements of the sizes of the centre and surround components of receptive fields. Transient cells had larger surrounds than sustained; the distributions were non-overlapping. Although the distributions of centre sizes overlapped, the transient cells had very significantly larger centres on average.2. There were characteristic differences in area-threshold and annulus-threshold curves and shapes of responses to brief and long flashes of light, and relative differences in the nature of surround adaptation and maintained discharge rates.3. The distinction of sustained from transient units survived over a wide range of backgrounds including the two principle reorganizations of function: relative weakening of surround components at low background; Purkinje shift at high.4. Sustained and transient units were differentially distributed in the retina: there was an overwhelming preponderance of sustained units in the area centralis.5. It is proposed that the transient units are the so-called multidendritedeep cells and the sustained units are the variously styled small ganglion cells.

Action Potentials↗
PubMed1971

Sustained and transient neurones in the cat's retina and lateral geniculate nucleus.

1. Cat retinal ganglion cells may be subdivided into sustained and transient response-types by the application of a battery of simple tests based on responses to standing contrast, fine grating patterns, size and speed of contrasting targets, and on the presence or absence of the periphery effect. The classification is equivalent to the ;X'/;Y' (linear/nonlinear) subdivision of Enroth-Cugell & Robson which is thus confirmed and extended.2. The sustained/transient classification applied to both on-centre and off-centre cells.3. Lateral geniculate neurones may be similarly classified by the same tests. Occasional concentrically organized cells had a mixture of sustained and transient properties.4. A technique for simultaneous recording from a geniculate neurone and one or more retinal ganglion cells providing its excitatory input showed that the connexions were specific with respect to the sustained/transient classification as well as the on-centre/off-centre classification. Most geniculate neurones are excitatorily driven only by retinal ganglion cells of the same functional type. In a few cases the inputs were mixed but only with respect to the sustained/transient classification.5. Sustained retinal ganglion cells had slower-conducting axons than the transient type. The same was true for lateral geniculate neurones but in this case the distributions showed considerable overlap.6. The sustained/transient classification is the functional correlate for the well-known segregation of optic nerve fibres into two conduction groups.7. The pathways carrying sustained and transient information remain essentially separate from retina through the lateral geniculate nucleus to the striate cortex.

Action Potentials↗
PubMed1970

Quantitative aspects of gain and latency in the cat retina.

1. The gain of the central response mechanism and the latency of the pure central response of on-centre ganglion cells were studied by recording from single optic tract fibres the responses evoked by slow square-wave stimuli applied against some steady background.2. The concept of effective flux was introduced and defined: if any portion of a stimulus extends beyond Ricco's area of complete summation, then that stimulus has an actual flux, equal to the product of its area and luminance, but it also has an effective flux which is that fraction of its actual flux which equals the actual flux of another stimulus which, when it falls entirely within Ricco's area, evokes an isobolic pure central response or has the same adaptive effect upon the central response mechanism as the first stimulus.3. The most significant finding was that when the cell responded with a pure central response to the incremental flux (the square wave) applied against a steady effective background flux, then the gain and the latency were functions exclusively of the sum of the two fluxes (the total flux), not of the incremental or background flux as such. This shows that the level of field adaptation of the central mechanism is reset within the latent period of the response to an incremental flux.4. Increment sensitivity curves based on isobolic suprathreshold responses all had the same slope of 0.9, when the log of the incremental flux was plotted against the log of the total flux. A plot of log latency against log total effective flux had a slope of -0.1.5. The stimulus-response relation derived from (3) and (4) was [Formula: see text] and [Formula: see text], where R is the response amplitude, F(et) the total flux, DeltaF(e) the incremental flux and K(1) and K(2) are constants.

Adaptation, Ocular↗
PubMed1968

Quantitative aspects of sensitivity and summation in the cat retina.

1. Properties of the central response mechanism of on-centre ganglion cells in the cat retina were studied by recording, from optic tract fibres, responses evoked by stimuli modulated with time in a sinusoidal or square-wave fashion.2. The shape of averaged square-wave responses resulting from the central mechanism alone was identified. This shape was identical from one cell to another. Such an identification permits the early recognition of peripheral antagonism.3. Threshold sensitivity for a sinusoidal stimulus was determined for fifty cells along one horizontal and vertical axis, passing through the most sensitive portion of the receptive field. These sensitivity profiles were described in terms of a central segment of constant maximum sensitivity (uniform centre) and sloping outer segments of exponentially decreasing sensitivity (exponential annulus). The dimensions of the uniform centre (horizontal axis x vertical axis) varied from 0.1 degrees x 0.1 degrees to 2.5 degrees x 2.2 degrees , the half width of the exponential annulus ranged from 0.1 degrees to 0.63 degrees .4. Adapting spots of varying diameter were placed concentric with the receptive field and the (unmodulated) luminance, at each diameter, that reduced a small central (sinusoidal) stimulus to threshold, was determined. The resulting area-adaptation curve, (adapting luminance plotted against diameter) showed that within defined limits the state of adaptation is determined by the flux independent of its distribution.5. Sinusoidal stimuli of varying diameter were placed concentric with the receptive field and the threshold luminance at each diameter was determined. Suprathreshold square-wave stimuli indicated that the central mechanism alone contributed to the response. These area-sensitivity curves did not show any decrease in sensitivity at larger diameters.6. The shape of the area-sensitivity curve, and hence the extent of the summating area, was found to be independent of the state of adaptation.7. For any one cell the shapes of the area-adaptation and area-sensitivity curves were shown to be identical, indicating that adapting flux and stimulus flux are independent of distribution over the same defined limits.8. The sensitivity of combinations of small disconnected areas of the receptive field was found to be equal to the sum of their individual sensitivities.

Action Potentials↗
PubMed1968

The angular selectivity of visual cortical cells to moving gratings.

1. Grating patterns were used to obtain a quantitative description of cells in the visual cortex of the cat whose response amplitude depended critically upon the orientation of the moving grating.2. In all such cells the impulse frequency was found to decrease linearly with angle on either side of an optimum angle (the preferred angle) until the response fell to zero or to a base frequency. The angular rate of change of response varied between cells and was expressed as the half-width at half amplitude (the angular selectivity).3. The angular selectivity of thirty-five cells was determined and more than half (nineteen) of these fell within the range 14-26 degrees .4. Fourteen cells responded optimally only when the grating was moved in one direction. Twenty-one cells responded optimally to two directions of movement 180 degrees apart, but the response in the two directions was not always equal.5. No significant correlation was found between the response amplitude at the optimum angle and the angular selectivity.6. The distribution of preferred angles did not show any difference between the oblique orientations and the vertical and horizontal orientations.7. These results are compared with a previous psychophysical estimate of angular selectivity.

Journal Article↗