Theta power and coherence illustrate cerebral processing of octave illusion

Abstract

Background: Understanding how cerebral regions are synchronized when hearing illusions might help to explain some of the mechanisms of hallucination in psychiatric disorders. EEG theta coherence in response to the octave illusion in healthy volunteers might be used for this purpose. Methods: Right-handed healthy volunteers were invited to hear silence, normal and reversed sequences of the octave illusion. Results: After hearing both normal and reversed sequences of the octave illusion, 11 people reported hearing the high tone in the left ear (RL) and 18 in the right (RR). The task-related power change in the right frontal and temporal areas and the task-related coherence difference in the right medial frontal and temporal areas were significantly increased in the RR group compared to the RL group. Conclusion: When processing the octave illusion, the right ear predominance was linked to a higher reactivity in the right frontal and right temporal areas in healthy right-handers.

EEG Theta Power and Coherence to Octave Illusion in First-Episode Paranoid Schizophrenia with Auditory Hallucinations

“…Documents have shown that the theta band is induced via the limbic-hippocampal-cortical feedback loop and is auditory specific [25,26,27]. Although other frequency bands exist, such as gamma rhythm, which is related to the GABA/glutamate interplay, our previous results [28] have demonstrated that the low-frequency theta band is specific to octave illusion response. Moreover, the theta band often acts as a windowing mechanism which determines the threshold and polarity of synaptic modifications [29] and is associated with positive symptoms of schizophrenia [30].…”

“…Based on previous neuroanatomic and neurophysiologic results [48,49], as well as our previous research with healthy participants [28], we selected a set of electrodes of interest and computed the coherence based on the EEG powers obtained in the following electrodes: Fc1, Fc2, T7, T8, Cp5, Cp6, Cp1, Cp2, P3, and P4. In order to gain the intra- and interhemispheric coherence, we excluded the midline and mastoid electrodes from further analysis, as suggested by Dien [50].…”

“…Whether the theta activity could supply evidence to support the corollary discharge dysfunction hypothesis in schizophrenia is still unclear. Nevertheless, the spectral power and coherence of the theta band were more pronounced in the frontal-temporal areas when processing the octave illusion in healthy right-handers [28]. Moreover, when hearing a ‘high-low' word illusion which was derived from the octave illusion [36], Chinese participants reported hearing meaningful Chinese words which were closely related to their personality traits [37].…”