Increase of neuronal response variability at higher processing levels as revealed by simultaneous recordings

Area of Science:

• Neuroscience
• Auditory System Physiology
• Sensory Information Processing

Background:

• Neuronal spike train variability poses a challenge for accurate sensory signal encoding.
• Understanding how variability changes across processing levels is crucial for deciphering neural computation.

Purpose of the Study:

• To quantify interspike-interval variability (coefficient of variation) and spike-count variability (Fano factor) in the locust auditory system.
• To investigate whether variability is generated or reduced during synaptic transmission and processing across three neural levels.

Main Methods:

• Simultaneous intracellular recordings from the first three processing levels of the locust metathoracic auditory system.
• Single-cell recordings to confirm findings.
• Comparison of variability in interneurons coding for sound direction versus sound patterns.

Main Results:

• Both interspike-interval and spike-count variability increased from peripheral auditory receptors to higher processing levels.
• Variability was consistently lower than predicted by a Poisson process and showed a strong dependence on spike rate.
• Interneurons processing sound patterns exhibited greater reliability than those processing sound direction.

Conclusions:

• Spike train variability increases with neural processing in the locust auditory system.
• Spike rate differences largely explain observed variability changes across processing levels.
• The locust auditory system exhibits more reliable neural coding than expected, particularly at interneuron levels.