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Neocortical axon arbors trade-off material and conduction delay conservation
Julian M L Budd1, Krisztina Kovács, Alex S Ferecskó
1School of Informatics, University of Sussex, Brighton, United Kingdom. j.m.l.budd@susx.ac.uk
Plos Computational Biology
|March 20, 2010
Summary
Brain wiring is not purely about saving space or time. New research shows that a slight excess in axon length optimizes neural communication speed and precision in the cerebral cortex.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Brain Anatomy
Background:
- The brain's complex network relies on axons for rapid information transfer.
- Axon morphology dictates information flow, with Cajal's conservation laws proposing wire length and conduction delay as key regulators.
- The precise spatial and temporal costs of neocortical axons remain largely undefined.
Purpose of the Study:
- To empirically investigate Ramón y Cajal's conservation laws for whole three-dimensional (3D) axon arbors in the cerebral cortex.
- To define the spatial and temporal communication costs of single neocortical axons.
- To understand how axon branching principles optimize neuronal network communication.
Main Methods:
- Reconstruction of in vivo labeled excitatory spiny and inhibitory basket cell intracortical axons.
- Application of various graph optimization algorithms to analyze axon arbors.
- Empirical investigation of Cajal's conservation laws in the cerebral cortex.
Main Results:
- Intracortical axons were found to be significantly longer than theoretically optimal.
- The temporal cost of cortical axons was suboptimal but superior to wire-minimized arbors.
- Cortical axon branching promotes low temporal dispersion of axonal latencies and a strong correlation between cortical distance and latency.
- Inhibitory basket cell axons may exhibit narrower latency windows than excitatory spiny cell axons, potentially enhancing signal detection.
Conclusions:
- A modest excess of axonal wire is traded off to enhance arbor temporal economy and precision for optimized neuronal network communication.
- These findings provide insights into brain organization and communication principles.
- Temporal precision is critical for coincidence detection, synchronization, and rapid network oscillations in grey matter development.
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The axon attaches to the cell body at a cone-shaped elevation called the axon hillock. The initial part of the axon, closest to the hillock, is known as the initial segment.
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