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Coding movement direction by burst firing in electrosensory neurons
Navid Khosravi-Hashemi1, Eric S Fortune, Maurice J Chacron
1Department of Physiology, McGill University, Montreal, Canada.
Journal of Neurophysiology
|July 22, 2011
Summary
Directional selectivity in fish brain circuits is enhanced by neuronal bursting. Bursts, not just spike counts, carry crucial directional information, decoded by downstream neurons.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Sensory Processing
Background:
- Directional selectivity is a key neural computation for processing movement.
- Traditional measures focus on action potential counts, neglecting spike train patterns like bursts.
- Sensory neurons often exhibit patterned firing, including bursts, which may influence selectivity.
Purpose of the Study:
- To investigate the role of neuronal bursting in direction selectivity.
- To explore the mechanisms underlying burst generation and decoding in midbrain neurons.
- To compare the directional information encoded in bursts versus isolated spikes.
Main Methods:
- Recorded from midbrain neurons in weakly electric fish responding to moving objects.
- Differentiated bursts and isolated spikes using an interspike interval (ISI) threshold.
- Developed biologically plausible models for burst generation (afferent input, calcium channels) and decoding (synaptic facilitation).
- Tested models in vivo using calcium antagonists.
Main Results:
- Most recorded neurons exhibited both bursts and isolated spikes.
- Bursts showed significantly higher directional bias than isolated spikes or the full spike train.
- In vivo calcium channel blockade reduced bursting and diminished differences in direction selectivity.
- Computational models demonstrated that bursts encode directional information and can be decoded by downstream neurons via synaptic facilitation.
Conclusions:
- Neuronal bursting significantly contributes to direction selectivity in these neurons.
- Upstream mechanisms involving calcium channels generate directionally biased bursts.
- Downstream neurons can decode directional information encoded in bursts using synaptic facilitation.
- Patterned neural firing, specifically bursting, is critical for accurate sensory processing.
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