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Anatomic basis of sequence-dependent predictability exhibited by nigral dopamine neuron firing patterns
R E Hoffman1, W X Shi, B S Bunney
1Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut 06520-8099, USA.
Synapse (New York, N.Y.)
|February 17, 2001
Summary
Forebrain connections influence dopamine neuron activity in the substantia nigra. Disrupting these connections reduces the predictability of dopamine neuron firing patterns, suggesting a role for forebrain structures.
Area of Science:
- Neuroscience
- Dopaminergic Signaling
- Computational Neuroscience
Background:
- Dopamine (DA) neurons in the substantia nigra exhibit history-dependent firing patterns.
- Interspike intervals (ISIs) of these neurons are partially predictable from prior activity.
Purpose of the Study:
- To investigate the neuroanatomic origins of sequential relationships in nigral DA neuron ISIs.
- To determine the role of forebrain connections in shaping DA neuron firing predictability.
Main Methods:
- Recording ISI data from three groups of nigral DA neurons in rats: unlesioned controls, after full forebrain hemisection, and after partial hemisection.
- Analyzing sequential predictability of ISI data using forecasting algorithms.
Main Results:
- Full forebrain hemisection significantly reduced the sequential predictability of DA neuron ISIs compared to controls.
- Partial hemisection, which preserved forebrain connections, did not significantly reduce predictability.
- Maximum predictability in unlesioned rats involved approximately 3.7 prior events, suggesting a history dependence of ~600-800 ms.
Conclusions:
- Forebrain structures contribute to the sequence-dependent firing patterns of substantia nigra DA neurons.
- The findings support a model where forebrain interactions modulate the history dependence of DA neuron activity.
- Further research is needed to elucidate the functional significance of this history-dependent ISI structure.