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B G Cleland

Publications and source records attributed to B G Cleland.

At least 37 records · Page 2Linked to original sources
PubMed1982

Normality of spatial resolution of retinal ganglion cells in cats with strabismic amblyopia.

1. A convergent or divergent strabismus was induced surgically in eight kittens and a cyclotropia of about 90 deg in two additional kittens. 2. Behavioural measurements were made of the visual acuity of each eye for square-wave gratings. All eight animals that were so tested displayed a reduction of acuity in one eye relative to the other of 1.3-2.5 octaves. 3. The activity of retinal ganglion cells was recorded within the amblyopic eye of six cats, three with a convergent strabismus, two with a divergent strabismus and one with a cyclotropia. Measurements were made of the spatial resolution with 215 on-centre cells for horizontal and vertical gratings. 4. In contrast to other reports, we found the spatial resolution of ganglion cells in the amblyopic eye of the strabismic animals to be comparable to those of normal cats at all retinal eccentricities. In particular there was no evidence for a loss of resolution in the vicinity of the area centralis. 5. Measurement of the cross-sectional area of cells in the lateral geniculate nucleus (l.g.n.) revealed no evidence of cell shrinkage in laminae receiving a projection from the amblyopic eye. 6. Together, these findings lead to the conclusion that the neural deficit responsible for the strabismic amblyopia in these animals did not lie in the retina but rather at more central levels of the visual pathway.

Action Potentials↗
PubMed1980

Visual resolution of retinal ganglion cells in monocularly-deprived cats.

The spatial resolution of 87 on-centre retinal ganglion cells was measured at different retinal eccentricities in the retina of the deprived eye of two monocularly-deprived cats. Intra-ocular recording techniques were employed in order that particular attention could be placed on ganglion cells in the region of the area centralis. The spatial cut-off frequencies of both major classes on-centre ganglion cells were comparable to those observed in normal retinas at similar retinal eccentricities. In particular there was no evidence of any loss of spatial resolution of either class of cell in the vicinity of the area centralis as has been reported in the retina of the deviating eye of strabismic cats.

Animals↗
PubMed1979

Visual resolution and receptive field size: examination of two kinds of cat retinal ganglion cell.

Intraocular recordings from brisk-sustained and brisk-transient ganglion cells in the cat's retina revealed a systematic increase in center size and decrease in spatial cut-off frequency with increasing distance from the area centralis. At any one eccentricity sizes of the centers of sustained and transient cells did not overlap, and the variation in cut-off frequency for each class was constrained to about one-half octave.

Animals↗
PubMed1977

The retinal input to cells in area 17 of the cat's cortex.

The activity of retinal ganglion cells and cortical cells with overlapping receptive fields was simultaneously recorded. The responses to moving stimuli of individual simple cortical cells could be accounted for on the basis of the cell receiving either on-centre or off-centre afferents; instances in which it was necessary to postulate a mixed on- and off-centre input were not found. In six instances cross correlograms of ganglion cell and cortical cell activity showed that the ganglion cell was afferent, via a relay cell in the LGN, to the cortical neurone. The receptive fields of such pairs were almost completely overlapping and concentric. In three cases a sustained ganglion cell projected to a simple cortical cell. In one case a transient ganglion cell projected to a simple cell, and in one case a sustained and a transient ganglion cell projected to the same simple cell.

Afferent Pathways↗
PubMed1977

Organization of visual inputs to interneurons of lateral geniculate nucleus of the cat.

1. Two groups of interneurons that are involved in the organization of the lateral geniculate nucleus (LGN) are described. The cell bodies of one group lie within the LGN; these units are referred to as intrageniculate. The cell bodies of the other group are found immediately above the LGN at its border with the perigeniculate nucleus; these units are referred to as perigeniculate. 2. Intrageniculate interneurons have center-surround receptive fields that resemble those of relay (principal) cells. They can be subdivided into brisk or sluggish and sustained or transient categories. They are stimulated transsynaptically from the visual cortex and have a characteristic variation in the latency of their spike response to such stimulation both at threshold and for suprathreshold stimuli. The pathway for this stimulation appears to be via cortical efferents to the LGN. Intrageniculate interneurons receive direct, monosynaptic retinal inputs, as determined by recording simultaneously from such interneurons and from the ganglion cells which provide excitatory input to them. Similar to relay cells, they are shown to have one or two major ganglion cell inputs. 3. Perigeniculate interneurons are generally binocularly innervated and give on-off responses to small spot stimuli throughout their receptive field. They respond well to rapid movement of large targets. They respond to electrical stimulation of the retina with a spike latency that falls between that of brisk transient and brisk sustained relay cells. This latency is one synaptic delay longer than that of brisk transient relay cell activation and suggests that they are excited by axon collaterals of these relay cells. Electrical stimulation of the visual cortex is also consistent with this model; the latency of the response of perigeniculate interneurons is approximately one synaptic delay longer than the latency of the response of brisk transient relay cells. 4. The interneuronal pathways described are consistent with proposed circuits that subserve the generation of IPSPs that arise in response to optic nerve and visual cortical stimulation. We now show that such inhibition has feed-forward (intrageniculate) and feed-back (perigeniculate) components that are mediated by two different classes of geniculate interneurons. It is suggested that the intrageniculate interneurons are involved in precise, spatially organized inhibition and that the perigeniculate interneurons are part of a more general, diffuse inhibitory system that modulates LGN excitability.

Animals↗
PubMed1976

Lateral geniculate relay of slowly conducting retinal afferents to cat visual cortex.

1. Lateral geniculate neurones of the cat were studied in terms of the latency for activation by local electrical stimulation of the retina, the latency of electrical activation from the visual cortex and properties of receptive fields. Most of the units were relay cells (antidromic activation from visual cortex) but a small proportion were trans-synaptically activated from the cortex. The latter group included units with on-off, on-centre or off-centra receptive fields. 2. Direct activation of lateral geniculate neurones from local electrical stimulation of retinal ganglion cells or their axons in the retina was identified by the sharpness of timing of the elicited impulses. This procedure revealed the existence of slowly conducting axons relaying in the lateral geniculate nucleus. 3. The distribution of latencies for direct activation from the retina was bimodal with an extended tail of long values. It is similar to the distribution of antidromic latencies of retinal ganglion cells following stimulation of the optic tract. 4. There was a tendency for geniculate neurones with fast input from the retina to have fast axons to the visual cortex and correspondingly for medium-speed and slow input. 5. The previous classification of geniculate receptive fields into sustained and transient types was extended to include commonly encountered 'brisk' and uncommonly encountered 'sluggish' varieties of each. The extension was based on visual properties and latency for direct electrical activation from the retina. Units with receptive fields differing from the familiar on-centre or off-centre concentric pattern were encountered rarely; they included colour-coded fields, local-edge-detectors and one edge-inhibitory off-centre type.

Animals↗
PubMed1975

The distribution of the alpha type of ganglion cells in the cat's retina.

There is a distinct class of large ganglion cell bodies observable in whole-mount preparations of the cat's retina stained with cresyl violet. Measurements of perikaryal size and its variation with eccentricity from the central area support the identification of the large cells with the class of alpha cells previously defined in Golgi-stained preparations. A complete enumeration of alpha cells in one retina yielded a total of 6212. They were encountered in all parts of the retina and had a peak density within the central area ( 200/mm2). The retinal distribution was displayed as a contour map of alpha-cell density. Away from the central area, the lines of iso-density had the form of a 4-pointed star with rather blunt points corresponding to horizontal and vertical ridges of augmented density. Along horizontal, vertical and oblique strips through the central area, alpha-cell density was an approximately constant fraction of total ganglion cell-density. The average value of the fraction was 3.3% from which it has been calculated that the cat's retina may contain as many as 190,000 ganglion cells.

Animals↗
PubMed1975

Physiological identification of a morphological class of cat retinal ganglion cells.

1. Small selected patches of retina (approximately 1 mm2) were exhaustively searched electrophysiologically to identify every brisk-transient unit present. The patches were then marked by electrolytic lesions. 2. Whole-mount preparations were made from which the distribution of alpha cells within and around the marked areas could be obtained. 3. A one-to-one correspondence could be demonstrated between brisk-transient units and alpha cells. 4. The correspondence was maintained within a patch of retina including the central area. 5. The correspondences were subject to about 10% of uncertainty attributed to technical limitations of the method.

Animals↗
PubMed1974

Brisk and sluggish concentrically organized ganglion cells in the cat's retina.

1. Nine hundred and sixty cat retinal ganglion cells were evaluated with respect to receptive-field organization and latency to antidromic activation of their axons from optic-tract and mid-brain positions.2. The vast majority (92%) had the familiar concentric centre/surround organization. As in earlier work these could be classed as sustained or transient, independently of the centre type. About 13% of the concentric cells were characterized by relatively sluggish responses to conventional visual stimuli which yielded brisk responses from the others. The sluggish cells constituted a previously unspecified class of concentric receptive fields.3. The responses of brisk and sluggish cells to a variety of stimuli were described with a view to developing procedures for distinguishing them on functional grounds.4. Measurements of latency to antidromic activation of retinal axons confirmed earlier work in showing that cells classed as brisk-transient had the shortest conduction times from the optic tract. Cells classed as brisk-sustained had intermediate conduction times and from earlier work would constitute an important input to the lateral geniculate nucleus. A proportion of the brisk-sustained axons reached the pretectal region (especially on-centre types) and a small minority reached the superior colliculus (especially off-centre types).5. Sluggish cells had generally slower antidromic conduction times; despite some overlap with the brisk-sustained class, the slower conduction provided independent support for the functional differentiation. Sluggish axons reached the pretectal region and superior colliculus.6. The brisk-sustained cells constituted the majority of the recordings in the area centralis.7. A comparison with the morphological data of Boycott & Wässle is made which suggests that the brisk-transient units corresponded with alpha cells, the brisk-sustained with beta cells, and the sluggish units were included amongst the gamma cells.

Animals↗