Receptive field sizes and neuronal encoding bandwidth are constrained by axonal conduction delays

Area of Science:

• Neuroscience
• Computational Neuroscience
• Sensory Systems Biology

Background:

• Population coding models often assume simultaneous presynaptic spike arrival.
• Natural neuronal signaling involves time delays due to spatial spread and conduction velocity.
• Understanding these delays is crucial for accurate models of neural information processing.

Purpose of the Study:

• To analyze the effects of population size and axonal conduction delays on stimulus encoding performance.
• To investigate how these factors influence the electrosensory system of the electric fish Apteronotus leptorhynchus.
• To determine the trade-offs between receptive field size, conduction delays, and encoding efficiency.

Main Methods:

• Experimental localization of electroreceptor afferents along the fish's body axis.
• Relating afferent locations to neurophysiological response properties.
• Information-theoretical analysis of coding performance in homogeneous and heterogeneous neuronal populations using computational models (LIF neurons).

Main Results:

• Information encoding increases with population size.
• Heterogeneous populations generally outperform homogeneous ones when conduction delays are compensated.
• Significant spread in neuronal conduction delays severely impairs the encoding of high-frequency stimulus components.
• Receptive field sizes in the electrosensory lateral line lobe represent a balance between delay spread and encoding performance.

Conclusions:

• Axonal conduction delays are a fundamental constraint on neural information processing in converging networks.
• These delays limit the bandwidth of natural stimuli and the effective size of neuronal populations.
• The findings have implications for understanding the optimal design principles of nervous systems.