Similar EEG Activity Patterns During Experimentally-Induced Auditory Illusions and Veridical Perceptions

Area of Science:

• Neuroscience
• Cognitive Science
• Psychology

Background:

• Perception can deviate from sensory input due to internal brain states, leading to hallucinations and illusions.
• These phenomena occur in both patient and healthy populations and can be studied experimentally.
• Understanding the neural basis of altered perception sheds light on normal brain function and dysfunction.

Purpose of the Study:

• To investigate the neural correlates of auditory illusions in healthy subjects.
• To compare brain activity during illusory perceptions (false alarms) with actual perceptions (hits).
• To determine if neural markers of conscious perception differ when stimuli are absent versus present.

Main Methods:

• An auditory signal detection task was used, presenting speech snippets near the detection threshold in noise.
• Electroencephalography (EEG) was employed to record brain activity.
• Event-related potentials (ERPs) and event-related spectral perturbations (ERSPs) were analyzed, comparing hits, false alarms, misses, correct rejections, and button presses.

Main Results:

• Both hits and false alarms showed an early negativity (EN) and late positivity (LP), absent in other conditions.
• A common low-frequency power enhancement (<4 Hz) was observed in hits and false alarms.
• Hits exhibited significantly higher LP amplitude and low-frequency power than false alarms.

Conclusions:

• Neural correlates of conscious perception, including early negativity and late positivity, are present in both actual and illusory auditory experiences.
• Low-frequency brain oscillations are associated with auditory awareness, regardless of external stimulus presence.
• The study demonstrates that neural mechanisms of conscious perception can be triggered by internal brain states, not solely by external stimuli.