Deviance detection based on regularity encoding along the auditory hierarchy: electrophysiological evidence in humans

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cognitive Neuroscience

Background:

• Deviance detection in the acoustic environment is vital for survival, enabling awareness of potentially relevant external events.
• Human mismatch negativity (MMN), an EEG response, was traditionally linked to late cortical processing (100-200 ms) of acoustic regularity violations.
• Animal studies revealed much earlier (20-30 ms) deviance detection at lower auditory pathway levels, suggesting a conserved mechanism.

Purpose of the Study:

• To review evidence on human auditory deviance detection mechanisms and their neural correlates.
• To compare human auditory deviance detection latencies and neural networks with those observed in animal models.
• To investigate the hierarchical organization of regularity encoding and deviance detection in the human auditory system.

Main Methods:

• Review of recent evidence using complex auditory brainstem response (cABR), middle latency response (MLR), and magnetoencephalography (MEG).
• Analysis of neural responses to violations of simple acoustic regularities (e.g., frequency, location changes).
• Analysis of neural responses to violations of complex regularities (e.g., alternating tones, feature conjunctions).

Main Results:

• Human auditory deviance detection for simple acoustic features occurs rapidly (MLR latency range) in lower auditory structures, including the brainstem and distinct cortical regions.
• These early responses are independent of refractoriness and differ from the generators of the longer-latency MMN.
• Violations of complex regularities elicit MMNs, indicating a hierarchical processing of regularity complexity.

Conclusions:

• Auditory deviance detection is a fundamental principle of auditory system organization, operating across multiple levels.
• Simple acoustic regularity encoding and deviance detection occur early in the auditory pathway, from brainstem to cortex.
• The auditory system processes regularity complexity hierarchically, with simpler violations detected rapidly and complex ones engaging later cortical mechanisms like MMN.