Morphology of the turtle accessory optic system

Martin, John R.; Kogo, Naoki; Fan, Tian Xing; Ariel, Michael

doi:10.1017/s0952523803206064

Cited by 3 publications

(1 citation statement)

References 41 publications

(67 reference statements)

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“…However, the variability of these experiments suggests that there are different positions of PT synapses along the BON dendrite, but not only on spines. Having some PT synapses onto spines could not account for a lack of RET attenuation because BON neurons lack spines (Martin et al 2004). PT synapses are more likely on distal dendrites where some can interact with RET synapses.…”

Section: Location Of Synapses On Bon Membranementioning

confidence: 99%

Shunting Inhibition in Accessory Optic System Neurons

Ariel

Kogo²

2005

Journal of Neurophysiology

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. The interaction of excitatory and inhibitory inputs to the accessory optic system was studied with whole cell recordings in the turtle basal optic nucleus. Previous studies have shown that visual patterns, drifting in the same preferred direction, evoke excitatory and inhibitory postsynaptic events simultaneously. Analysis of the reversal potentials for these events and their pharmacological profile suggest that they are mediated by AMPA and GABA A receptors, respectively. Here, neurons were recorded to study nonlinear interaction between excitatory and inhibitory responses evoked by electrical microstimulation of the retina and pretectum, respectively. The responses to coincident activation of excitatory and inhibitory inputs exhibited membrane shunting in that the excitatory response amplitude, adjusted for changes in driving force, was attenuated during the onset of the inhibitory response. This nonlinear interaction was seen in many but not all stimulus pairings. In some cases, attenuation was followed by an augmentation of the excitatory response. For comparison, the size of the excitatory response was evaluated during a hyperpolarizing current pulse that directly modulated voltage-sensitive channels of a slow rectifying I h current. Injection of hyperpolarizing current did not cause the attenuation of the excitatory synaptic responses. We conclude that there is a nonlinear interaction between these excitatory and inhibitory synaptic currents that is not due to hyperpolarization itself, but probably is a result of their own synaptic conductance changes, i.e., shunting. Since these events are evoked by identical visual stimuli, this interaction may play a role in visual processing. I N T R O D U C T I O NNeurons may receive tens of thousands of synaptic inputs that are integrated throughout its membrane, often resulting in spike initiation at the axon hillock near the soma. This synaptic integration occurs during a temporal overlap of synaptic events that involve different synaptic conductances (e.g., excitatory and inhibitory responses; Qian and Sejnowski 1990). The experiments here investigate synaptic integration on a membrane level in a system for which it has been shown that natural stimuli evoke simultaneous excitatory and inhibitory inputs onto the same cell (Ariel and Kogo 2001). These cells in the accessory optic system relay retinal slip information to the cerebellum and numerous brain stem nuclei for compensatory head and eye movements (Brecha and Karten 1979;Simpson 1984).The accessory optic system receives direct excitatory input from the retina (Kogo and Ariel 1997;Zhang and Eldred 1994) and indirect inhibitory input from the pretectum (Kogo et al. 2002). Both excitatory and inhibitory responses to pattern motion on the contralateral retina are direction-sensitive (Ariel and Kogo 2001). Surprisingly, these two inputs shared a similar preferred direction such that excitatory and inhibitory synaptic events reach the membrane simultaneously.To study synaptic integration of these two inputs, mi...

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Section: Location Of Synapses On Bon Membranementioning

confidence: 99%

Shunting Inhibition in Accessory Optic System Neurons

Ariel

Kogo²

2005

Journal of Neurophysiology

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Localization of GABA (γ-aminobutyric acid) markers in the turtle's basal optic nucleus

Martin

Ariel

2005

Brain Research

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The accessory optic system: basic organization with an update on connectivity, neurochemistry, and function

Giolli

Blanks

Lui

2006

Progress in Brain Research

143

123

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The accessory optic system (AOS) is formed by a series of terminal nuclei receiving direct visual information from the retina via one or more accessory optic tracts. In addition to the retinal input, derived from ganglion cells that characteristically have large receptive fields, are direction-selective, and have a preference for slow moving stimuli, there are now well-characterized afferent connections with a key pretectal nucleus (nucleus of the optic tract) and the ventral lateral geniculate nucleus. The efferent connections of the AOS are robust, targeting brainstem and other structures in support of visual-oculomotor events such as optokinetic nystagmus and visual-vestibular interaction. This chapter reviews the newer experimental findings while including older data concerning the structural and functional organization of the AOS. We then consider the ontogeny and phylogeny of the AOS and include a discussion of similarities and differences in the anatomical organization of the AOS in nonmammalian and mammalian species. This is followed by sections dealing with retinal and cerebral cortical afferents to the AOS nuclei, interneuronal connections of AOS neurons, and the efferents of the AOS nuclei. We conclude with a section on Functional Considerations dealing with the issues of the response properties of AOS neurons, lesion and metabolic studies, and the AOS and spatial cognition. The accessory optic system (AOS) is formed by a series of terminal nuclei receiving direct visual information from the retina via one or more accessory optic tracts. In addition to the retinal input, derived from ganglion cells that characteristically have large receptive fields, are direction-selective and have a preference for slow moving stimuli, there are now well characterized afferent connections with a key pretectal nucleus (nucleus of the optic tract) and the ventral lateral geniculate nucleus. The efferent connections of the AOS are robust, targeting brainstem and other structures in support of visual-oculomotor events such as optokinetic nystagmus and visual-vestibular interaction. The present chapter reviews the newer experimental findings while including older data concerning the structural and functional organization of the AOS. We then consider the ontogeny and phylogeny of the AOS and include a discussion of similarities and differences in the anatomical organization of the AOS in nonmammalian and mammalian species. This is followed by sections dealing with retinal and cerebral cortical afferents to the AOS nuclei, interneuronal connections of AOS neurons, and the efferents of the AOS nuclei. We conclude with a section on Functional Considerations dealing with the issues of the response properties of AOS neurons, lesion and metabolic studies, and the AOS and spatial cognition.

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Morphology of the turtle accessory optic system

Cited by 3 publications

References 41 publications

Shunting Inhibition in Accessory Optic System Neurons

Shunting Inhibition in Accessory Optic System Neurons

Localization of GABA (γ-aminobutyric acid) markers in the turtle's basal optic nucleus

The accessory optic system: basic organization with an update on connectivity, neurochemistry, and function

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