Frequency-dependent effects of glutamate antagonists on the vestibulo-ocular reflex of the cat

Priesol, Adrian J.; Jones, Gavin E. G.; Tomlinson, R. D.; Broussard, Dianne M.

doi:10.1016/s0006-8993(99)02441-5

Cited by 14 publications

(6 citation statements)

References 56 publications

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“…The hypothesis that NMDA receptors make a significant contribution to frequency filtering at vestibular synapses was therefore not supported. A weak effect of NMDA blockade was observed, which could have contributed to the effect of NMDA antagonists on the frequency response of the VOR in alert animals (Priesol et al. , 2000).…”

Section: Discussionmentioning

confidence: 99%

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Dynamics of glutamatergic synapses in the medial vestibular nucleus of the mouse

Broussard

2009

Eur J of Neuroscience

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During sinusoidal rotation or translation, primary vestibular afferents modulate their discharge rates at the frequency of motion, effectively transmitting frequency-modulated (FM) signals. This study indicates a possible role for excitatory synapses in the processing of FM signals by vestibular brainstem pathways. Inputs to medial vestibular neurons were activated with FM pulse trains, while inhibitory transmission was blocked. The relationship between the presynaptic pulse rate and the postsynaptic membrane potential was found to be linear within a range of pulse rates. Short-term plasticity was a factor contributing to sensitivity at higher modulating frequencies. The amount of low-pass filtering was correlated with excitatory postsynaptic potential (EPSP) shape, which affected temporal summation during the train. Although the NMDA component of glutamatergic transmission affected EPSP shape, it made only a minor contribution to the dynamics of synaptic transmission. Most responses showed low-pass filtering over the entire 1-16 Hz range. Overall, excitatory synapses in the medial vestibular nucleus contribute a low-pass filter to central vestibular processing and complement the high-pass filtering that is introduced both by peripheral vestibular dynamics and by the intrinsic dynamics of secondary vestibular neurons.

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Section: Discussionmentioning

confidence: 99%

“…, 1994). Blockade of NMDA receptors affects VOR dynamics in vivo (Priesol et al. , 2000), suggesting that the NMDA component may contribute low‐pass filtering dynamics to central vestibular synapses.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of glutamatergic synapses in the medial vestibular nucleus of the mouse

Broussard

2009

Eur J of Neuroscience

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“…The observation that frequency-tuned coding channels seem to have distinct pharmacological properties supports this idea. Administration of NMDA receptor antagonists reduces low-frequency, but not high-frequency, VOR gain (Priesol et al 2000). Thus NMDA receptors may be selectively present in the low-frequency coding channels, and they could endow the low-frequency channels with plasticity mechanisms different from those found in the high-frequency channels.…”

Section: Generalizationmentioning

confidence: 97%

CEREBELLUM-DEPENDENT LEARNING: The Role of Multiple Plasticity Mechanisms

Boyden

Katoh

Raymond

2004

Annu. Rev. Neurosci.

407

306

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The cerebellum is an evolutionarily conserved structure critical for motor learning in vertebrates. The model that has influenced much of the work in the field for the past 30 years suggests that motor learning is mediated by a single plasticity mechanism in the cerebellum: long-term depression (LTD) of parallel fiber synapses onto Purkinje cells. However, recent studies of simple behaviors such as the vestibulo-ocular reflex (VOR) indicate that multiple plasticity mechanisms contribute to cerebellum-dependent learning. Multiple plasticity mechanisms may provide the flexibility required to store memories over different timescales, regulate the dynamics of movement, and allow bidirectional changes in movement amplitude. These plasticity mechanisms must act in combination with appropriate information-coding strategies to equip motor-learning systems with the ability to express learning in correct contexts. Studies of the patterns of generalization of motor learning in the VOR provide insight about the coding of information in neurons at sites of plasticity. These principles emerging from studies of the VOR are consistent with results concerning more complex behaviors and thus may reflect general principles of cerebellar function.

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“…Blockade of N-methyl-D-aspartate (NMDA) receptors has a selective effect on the low-frequency VOR, which is not duplicated by blockade of other types of ionotropic glutamate receptors (Priesol et al 2000). NMDA receptors have a known role in synaptic plasticity in many systems and also are known to contribute to the commissural connections between the vestibular nuclei on the two sides of the brainstem (Knöpfel 1987;Doi et al 1990).…”

Section: Can Learning Be Applied To Different Stimuli?mentioning

confidence: 99%

Learning in a Simple Motor System

Broussard¹,

Kassardjian²

2004

Learn. Mem.

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Motor learning is a very basic, essential form of learning that appears to share common mechanisms across different motor systems. We evaluate and compare a few conceptual models for learning in a relatively simple neural system, the vestibulo-ocular reflex (VOR) of vertebrates. We also compare the different animal models that have been used to study the VOR. In the VOR, a sensory signal from the semicircular canals is transformed into a motor signal that moves the eyes. The VOR can modify the transformation under the guidance of vision. The changes are persistent and share some characteristics with other types of associative learning. The cerebellar cortex is directly linked to the VOR reflex circuitry in a partnership that is present in all vertebrates, and which is necessary for motor learning. Early theories of Marr, Albus, and Ito, in which motor memories are stored solely in the cerebellar cortex, have not explained the bulk of the experimental data. Many studies appear to indicate a site of learning in the vestibular nuclei, and the most successful models have incorporated long-term memory storage in both the cerebellar cortex and the brainstem. Plausible cellular mechanisms for learning have been identified in both structures. We propose that short-term motor memory is initially stored in the cerebellar cortex, and that during consolidation of the motor memory the locus of storage shifts to include a brainstem site. We present experimental results that support our hypothesis.In many situations, inaccurate movements are worse than useless. If the movement is slow, errors can be corrected online by visual or other sensory feedback. However, rapid movements must be intrinsically accurate. This could be accomplished by hard-wiring an accurate movement, which has the obvious disadvantage that the movement cannot be readjusted for changes in downstream motor centers or (in the case of a reflex) for changes in sensory sensitivity. A better solution is to calibrate the movement by trial and error, that is, by motor learning. For our purposes, motor learning is defined as the process by which we acquire precise, coordinated movements, like those that are required in order to run, serve a tennis ball, and type accurately. Because accurate movements are necessary whenever predators must be avoided or prey captured, we can speculate that motor learning may have been one of the earliest types of associative learning to evolve. It has been demonstrated in the ventral nerve cord of insects (Horridge 1962) and is probably universal in freely-moving animals. Furthermore, because its substrate can be relatively simple and well understood, there is a real possibility of understanding motor learning both on the molecular level and on the level of brain circuitry.Motor learning is classified as procedural learning. Errors are monitored and used to guide adaptive changes without conscious awareness. Instead of learning a concept, the subject learns an accurate and appropriate motor response. Distinctions have also been made b...

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Frequency-dependent effects of glutamate antagonists on the vestibulo-ocular reflex of the cat

Cited by 14 publications

References 56 publications

Dynamics of glutamatergic synapses in the medial vestibular nucleus of the mouse

Dynamics of glutamatergic synapses in the medial vestibular nucleus of the mouse

CEREBELLUM-DEPENDENT LEARNING: The Role of Multiple Plasticity Mechanisms

Learning in a Simple Motor System

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