Excitatory and inhibitory receptive fields of tectal cells are differentially modified by magnocellular and parvocellular divisions of the pigeon nucleus isthmi

Y. Wang; J. Xiao; S.-R. Wang

doi:10.1007/s003590000102

The modulatory cholinergic system in goldfish tectum may be necessary for retinotopic sharpening

Visual Neuroscience ◽

10.1017/s095252380000674x ◽

1995 ◽

Vol 12 (6) ◽

pp. 1093-1103 ◽

Cited By ~ 19

Author(s):

John T. Schmidt

Keyword(s):

Transmitter Release ◽

Receptive Fields ◽

Optic Tract ◽

Receptor Activation ◽

Cholinergic Innervation ◽

Field Potentials ◽

Nucleus Isthmi ◽

Nerve Crush ◽

Normal Fish ◽

Retinal Fibers

AbstractThe cholinergic circuit within the tectum and the cholinergic input from the nucleus isthmi mediate a presynaptic augmentation of retinotectal transmitter release via nicotinic receptors. In this study, the cholinergic systems were either eliminated using the cholinergic neurotoxin AF64A or blocked using nicotinic antagonists to test for effects on the activity-driven sharpening of the regenerating retinotectal projection. The effectiveness of the AF64A was verified by recording field potentials elicited by optic tract stimulation and by immunohistochemical staining for choline acetyltransferase (ChAT). At 1 week after intracranial (IC) injection of AF64A (12 to 144 nmoles) into the fluid above the tectum, field potentials showed a selective dose-dependent decrement of the cholinergic polysynaptic component with no effect on the amplitude of the glutamatergic monosynaptic component. The decrement was only partially recovered in recordings at 2 and 6 weeks. In normal fish, the ChAT antibody stains a population of periventricular neurons, their apical dendrites, and a dense plexus within the optic terminal lamina that consists of their local axons and fine dendrites and of input fibers from the nucleus isthmi. One week after IC AF64A injection (48–72 nmoles), most immunostaining in superficial tectum was lost but most neuronal somas in the deep tectum could still be seen, and staining in the tegmentum below the tectum was completely intact. At 2 weeks and later, the staining of neuronal somata largely recovered, but staining of the superficial plexus did not. AF64A treatment at 18 days after nerve crush, when regenerating retinal fibers are beginning to form synapses, prevented retinotopic sharpening of the projection. Recordings showed a rough retinotopic map on the tectum but the multiunit receptive fields (MURFs) at each tectal point averaged 34 deg vs. 11 deg in vehicle-injected control regenerates. AF64A treatment before nerve crush also blocked sharpening, ruling out a direct effect on retinal growth cones or retinal fibers, as AF64A rapidly decomposes, whereas its effect on the cholinergic fibers is long-lasting. IC injection or minipump infusion of the nicotinic antagonists α-bungarotoxin (αBTX), neuronal bungarotoxin (nBTX), and pancuronium during regeneration also prevented sharpening (MURFs averaging 29.4 deg, 33.0 deg, and 31.4 deg, respectively). Control Ringer≈s solution infusions or injections over the same period (19–37 days postcrush) had no effect on regenerated MURF size (11.7 deg). The results show that the cholinergic innervation, which modulates transmitter release, is required for activity-driven retinotopic sharpening, thought to be triggered by NMDA receptor activation.

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Functional relationship between nucleus isthmi and tectum in teleosts: Synchrony but no topography

Visual Neuroscience ◽

10.1017/s0952523803203126 ◽

2003 ◽

Vol 20 (3) ◽

pp. 335-348 ◽

Cited By ~ 20

Author(s):

DAVID P.M. NORTHMORE ◽

SHAWN P. GALLAGHER

Keyword(s):

Optic Tectum ◽

Visual Information ◽

Small Amplitude ◽

Functional Relationship ◽

Visual Stimulation ◽

Functional Unit ◽

Receptive Fields ◽

Brain Structures ◽

Nucleus Isthmi ◽

Contralateral Eye

Neural activity in the optic tectum was compared with activity in the nucleus isthmi (NI) of both goldfish and sunfish with the aim of understanding how the two brain structures interact to process visual information. The two species yielded very similar results. Superficial tectum responds reliably to visual stimulation with topographically organized receptive fields; deep tectum and NI respond to stimulation throughout the field of the contralateral eye and habituate rapidly. Bursts of large-amplitude spiking in NI occur spontaneously and in response to contralateral visual stimulation. These NI bursts correlate with activity bursts across the tectal lobe on the same side, especially in the deeper layers. NI bursts may also synchronize with spiking activity in deep tectum. Trains of small-amplitude spikes in NI can be elicited by both ipsilateral and contralateral stimulation, but are not reflected in tectal activity. Simultaneous recordings from two sites in one NI were almost identical, suggesting that NI operates as a functional unit, broadcasting the same message across the ipsilateral tectal lobe.

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Ultrastructure of developing visual cortical synapses in the cat superior colliculus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100085083 ◽

1991 ◽

Vol 49 ◽

pp. 156-157

Author(s):

Caroline A. Miller ◽

Laura L. Bruce

Keyword(s):

Superior Colliculus ◽

Phosphate Buffer ◽

Receptive Fields ◽

Visual Cortical Area ◽

Cortical Synapses ◽

Visual Cortical ◽

And Function ◽

Phosphate Buffered Saline ◽

The Brain ◽

Cat Superior Colliculus

The first visual cortical axons arrive in the cat superior colliculus by the time of birth. Adultlike receptive fields develop slowly over several weeks following birth. The developing cortical axons go through a sequence of changes before acquiring their adultlike morphology and function. To determine how these axons interact with neurons in the colliculus, cortico-collicular axons were labeled with biocytin (an anterograde neuronal tracer) and studied with electron microscopy.Deeply anesthetized animals received 200-500 nl injections of biocytin (Sigma; 5% in phosphate buffer) in the lateral suprasylvian visual cortical area. After a 24 hr survival time, the animals were deeply anesthetized and perfused with 0.9% phosphate buffered saline followed by fixation with a solution of 1.25% glutaraldehyde and 1.0% paraformaldehyde in 0.1M phosphate buffer. The brain was sectioned transversely on a vibratome at 50 μm. The tissue was processed immediately to visualize the biocytin.

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