Field Properties Of Ganglion Cells Research Articles

Emergence of complex receptive field properties of ganglion cells in the developing turtle retina

1. Receptive field properties of adult retinal ganglion cells are well documented, but little is known about their development. We made extracellular recordings of activity from turtle retinal ganglion cells during embryogenesis (stages 22-26), during the first 40 days posthatching, and in adults. 2. From stage 22 the cells fired in spontaneous recurring bursts, and from stage 23 they responded to light. Polar plots of the responses to motion were highly anisotropic in early embryonic cells. More than 40% of embryonic cells exhibited multiaxis anisotropy, and only 6% were statistically isotropic. The incidence of anisotropic cells gradually decreased throughout development. The incidence of isotropic cells and the excitatory receptive field diameters of all ganglion cells gradually increased during development and their maturation coincided with the disappearance of the spontaneous bursts (2-4 wk posthatching). 3. Both sensitivities to stimulus orientation and direction of motion were observed at the earliest stages of development. However, orientation selectivity reached a peak incidence at hatching, whereas directional selectivity completely disappeared, only to reappear in adults. 4. These results show that mature spatiotemporal receptive field properties of retinal ganglion cells emerge from initially highly anisotropic properties, which may reflect an immature, polarized dendritic layout. Their maturation might be mediated by dendritic outgrowth and strengthening of excitatory synaptic connections, which could be induced by spontaneous activity and driven to maturation by exposure to light at birth. Mature directional selectivity seems to require visual experience or the late establishment of a specialized inhibitory synaptic drive.

Effects of dopamine and its agonists and antagonists on the receptive field properties of ganglion cells in the rabbit retina

We investigated the effects of dopamine and its agonists and antagonists on the receptive field properties of ganglion cells in the isolated eyecup preparation of the rabbit. In general, dopamine (20–250 μM) reduced the overall sensitivity of ganglion cells to light stimuli while increasing the spontaneous activity of off-center cells and decreasing the spontaneous activity of on-center cells and on-off directionally selective cells. Neither ( − )-apomorphine (8–82 μM) nor the selective D-2 agonist LY 141865 (7–85 μM) mimicked the effects of exogenous dopamine. Instead, both drugs altered the responses of ganglion cells in a manner similar to that of the selective D-1 antagonist SCH 23390. The latter at 4–41 μM: (1) selectively reduced the antagonistic surround responses of off-center cells; (2) changed the sustained excitatory responses of on-center sustained cells to spots of light into sustained inhibitory responses; (3) selectively reduced the leading edge responses of on-off directionally selective cells to moving light stimuli, and (4) decreased the spontaneous activity of off-center cells while increasing the spontaneous activity of on-center cells. The effects of the selective D-2 antagonist S-sulpiride (37–116 μM) on the responses of on-center cells resembled those of exogenous dopamine, while for off-center cells the effects of S-sulpiride were similar to those of ( − )-apomorphine and LY 141865. Results were compared with those obtained previously with dopamine antagonists haloperidol, fluphenazine and cis-flupenthixol 14 on ganglion cell responses in the intact rabbit eye. These three drugs were clearly acting at D-1 receptors. The present findings support a physiological role for D-2 receptors in visual processing in the rabbit retina, in particular the hypothesis that endogenous dopamine release is modulated by inhibitory D-2 autoreceptors. 4,5 They also suggest that one function of dopaminergic neurons may be to modulate the sensitivity of ganglion cells to light stimuli.

On and off pathways through amacrine cells in mammalian retina: The synaptic connections of “starburst” amacrine cells

The neural architecture of on and off pathways in mammalian retina is described, including the development of ideas leading to an understanding of the bisublaminar organization of the inner plexiform layer of the retina which supports these two pathways. The complexities of bipolar cell contributions are contrasted with the relative simplicity of ganglion cell organization with regard to bisublaminar architecture, and a key role is described for internuncial amacrine cells as specific targets for bipolar cells. Two very different kinds of amacrine cell are considered and compared, both of Which mediate bipolar input to ganglion cells. These are the rod (type II) amacrine cell, and the more recently discovered “starburst” amacrine cell, which is apparently cholinergic in function. As different as the wide-field starburst amacrine cells are from the narrow-field rod amacrine cells, they share important features. Both are interposed between bipolar and ganglion cells, and both have segregated regions of presynaptic boutons. They differ, however, in that rod amacrines may perform more specific functions related to receptive field center organization, while the functional role of starburst amacrines may be unrelated to receptive field properties of ganglion cells. The mirror-symmetry of type a and type b (off and on) starburst amacrine cells is described together with their synaptic circuitry. In contrast to the rod amacrine cell the output of starburst amacrines is exclusively to ganglion cells. Others have proposed a dual function for acetylcholine (ACh) in the retina. A unifying hypothesis is briefly sketched here which relates the pharmacology of ACh and the dendritic stratification of starburst amacrine cells to the form and function of ganglion cells. It is proposed that the amount of generalized synaptic excitation received from ACh starburst amacrine cells by a particular type of ganglion cell is largely a function of co-stratification of the ganglion cell's dendrites with the distal boutons of starburst amacrine cells.

Association amacrine cells could mediate directional selectivity in pigeon retina.

Ganglion cell receptive fields in the vertebrate retina are classified as ‘simple’ if they display mutually antagonistic, concentric on and off responses to stimulation by light1, or ‘complex’ if they respond maximally to a stimulus which moves in a certain direction or has a particular orientation2. One complex unit frequently reported is directionally selective3–6. It is excited by stimuli moving through its receptive field in only one direction, the preferred direction, and is inhibited by motion in the reverse or null direction. In species such as cats and monkeys which have a predominantly simple centre-surround organization of ganglion cell receptive fields, there is a low ratio of conventional (amacrine cell) to ribbon (bipolar cell) synapses in the inner plexiform layer, while in species such as pigeons and frogs which have a large percentage of complex ganglion cell receptive fields, there is a high ratio of conventional to ribbon synapses. It is therefore thought that amacrine cells, which are laterally interconnecting neurones in the inner plexiform layer, form the complex ganglion cell receptive field7,8. Although quantitative electron microscopy of the inner plexiform layer has indicated that amacrine cells may form the complex receptive field properties of ganglion cells, it offers no clues to the particular morphology of amacrine cells involved. I have therefore now studied amacrine cells in pigeon retina using Golgi impregnation in both whole-mounted and radially sectioned material to see whether there is a correlation between the morphology of amacrine cells and the receptive fields of ganglion cells. In 30 Golgi-impregnated retinas, I have found many different morphological types of amacrine cell. One of these is so clearly different from all other amacrine cells that it requires the separation of pigeon amacrine cells into two distinct classes, those which lack axons (class I cells) and those which have axons (class II cells).

Centrifugal control of the avian retina. III. Effects of electrical stimulation of the isthmo-optic tract on the receptive field properties of retinal ganglion cells

Single unit recording techniques were used in decerebrate, immobilized domestic chicks to investigate the effects of electrical stimulation of the peripheral end of the severed isthmo-optic tract on the receptive field properties of ganglion cells in the contralateral retina. Tract stimulation always worked to enhance ganglion cell visual responses and was never observed to depress them. However, activation of the tract did not itself generate ganglion cell firing and centrifugal effects were only apparent when the retinal cells were receiving visual stimulation. Visual stimuli such as large, centred spots which were normally ineffective in driving ganglion cells because they enroached on the inhibitory surround, often produced activity when combined with tract stimuli. Experiments with spots and annuli suggest that this centrifugal enhancement probably results from suppression of the inhibitory surround mechanisms (disinhibition) since in such cases tract stimuli were only effective when paired with both spot and annulus, and not with either target alone. Occasionally, the centrifugal input seemed to increase ganglion cell excitability through a direct effect on central excitatory mechanisms (facilitation), since in these cases tract stimulation produced considerably increased firing to small, centred spots whilst failing to exert any appreciable effect on responses to either the annulus alone, or the annulus in combination with the spot. The possible functional significance of these findings is discussed.