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Macroscopic and subcellular factors shaping population spikes.
P Varona1, J M Ibarz, L López-Aguado
1Departamento de Ingeniería Informática, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
Journal of Neurophysiology
|April 12, 2000
Summary
Population spikes (PS) result from synchronized action potential (AP) firing. Lowering AP temporal scatter and increasing cell numbers enhance dendritic contributions to PS, with internal resistance being a critical factor.
Area of Science:
- Computational neuroscience
- Electrophysiology
- Neuronal modeling
Background:
- Population spikes (PS) are extracellular signals generated by synchronous action potential (AP) firing in neurons.
- In hippocampal CA1 pyramidal neurons, APs invade dendrites, contributing somatic and dendritic currents to extracellular recordings.
- Understanding the factors shaping PS requires integrating subcellular current dynamics with macroscopic field potentials.
Purpose of the Study:
- To investigate macroscopic and subcellular factors influencing antidromic population spikes (PS) in the hippocampal CA1 region.
- To model the spatiotemporal map of antidromic PS using a multineuronal CA1 model within a volume conductor.
- To elucidate the contributions of somatic and dendritic currents to PS under varying conditions.
Main Methods:
- Developed and utilized a multineuronal CA1 model embedded in a volume conductor.
- Fitted the model to the spatiotemporal map of antidromic population spikes.
- Simulated effects of temporal scatter in APs, number of firing cells, sodium conductance, and internal resistance on PS generation.
Main Results:
- Reduced temporal scatter of APs decreased PS peak less than expected but increased relative dendritic current contribution.
- Increased firing cell numbers also augmented relative dendritic contribution due to differences in somatic and dendritic transmembrane current waveforms.
- Internal resistance was identified as a critical factor, with lower values facilitating dendritic AP spread and accelerating temporal overlap of currents, improving PS reproduction.
Conclusions:
- The waveform and origin (somatic vs. dendritic) of transmembrane currents significantly influence PS characteristics.
- Sodium conductance has differential effects on somatic unitary APs versus extracellular PS, particularly in different hippocampal layers.
- Model reconstruction of field potentials is a powerful approach for understanding neuronal interactions and potentially refining experimental measurements.