New methods for quantifying rapidity of action potential onset differentiate neuron types

Area of Science:

• Neuroscience
• Computational Biology

Background:

• Action potentials (APs) in mammalian neurons display rapid onset dynamics.
• Current methods for quantifying AP onset rapidity are subjective, often relying on arbitrary phase plot slopes.
• Discrepancies exist regarding the underlying mechanisms of sharp AP onsets, such as sodium channel activation or backpropagation.

Purpose of the Study:

• To develop and validate systematic methods for quantifying action potential onset rapidity.
• To compare the efficacy of new methods with existing techniques in distinguishing neuron types.
• To investigate the utility of AP onset rapidity as a biomarker for neuron classification.

Main Methods:

• Proposed novel quantification methods based on the peak width of the membrane potential's second-time derivative ([Formula: see text]).
• Measured AP rapidity using four methods: inverse of full-width at half maximum (IFWd2), inverse of half-width at half maximum (IHWd2), phase plot slope, and error ratio.
• Applied methods to four distinct cortical and hippocampal neuron types.

Main Results:

• The IFWd2 and IHWd2 methods demonstrated the lowest relative standard deviations among neurons of the same type.
• AP rapidity measurements using [Formula: see text] peak width methods significantly differentiated between neuron types.
• The IFWd2 method successfully distinguished all four analyzed neuron types.

Conclusions:

• Novel [Formula: see text] peak width methods offer enhanced sensitivity and reduced variability for quantifying AP onset rapidity.
• These systematic methods provide a reliable tool for classifying neuron types based on AP dynamics.
• The findings suggest AP onset rapidity is a valuable parameter for exploring mechanisms influencing AP initiation.