Causal involvement of medial inferior frontal gyrus of non-dominant hemisphere in higher order auditory perception: A single case study

• Published in: Cortex Vol. 163; pp. 57 - 65
• Main Authors: Osawa, Shin-ichiro, Suzuki, Kyoko, Asano, Eishi, Ukishiro, Kazushi, Agari, Dai, Kakinuma, Kazuo, Kochi, Ryuzaburo, Jin, Kazutaka, Nakasato, Nobukazu, Tominaga, Teiji
• Format: Journal Article
• Language: English
• Published: Italy Elsevier Ltd 01.06.2023
• Subjects: Acoustic Stimulation; Auditory Perception - physiology; Brain Mapping; Condition context; Electrical stimulation; Electrocorticography; Epilepsy; Female; Humans; Magnetic Resonance Imaging; Medial inferior frontal gyrus; Non-dominant hemisphere; Prefrontal Cortex; Subjective auditory perception; Subjective auditory perception; Electrical stimulation; Medial inferior frontal gyrus; Non-dominant hemisphere; Condition context
• ISSN: 0010-9452; 1973-8102
• DOI: 10.1016/j.cortex.2023.02.007

The medial side of the operculum is invisible from the lateral surface of cerebral cortex, and its functions remain largely unexplored using direct evidence. Non-invasive and invasive studies have proved functions on peri-sylvian area including the inferior frontal gyrus (IFG) and superior temporal gyrus within the language-dominant hemisphere for semantic processing during verbal communication. However, within the non-dominant hemisphere, there was less evidence of its functions except for pitch or prosody processing. Here we add direct evidence for the functions of the non-dominant hemisphere, the causal involvement of the medial IFG for subjective auditory perception, which is affected by the context of the condition, regarded as a contribution in higher order auditory perception. The phenomenon was clearly distinguished from absolute and invariant pitch perception which is regarded as lower order auditory perception. Electrical stimulation of the medial surface of pars triangularis of IFG in non-dominant hemisphere via depth electrode in an epilepsy patient rapidly and reproducibly elicited perception of pitch changes of auditory input. Pitches were perceived as either higher or lower than those given without stimulation and there was no selectivity for sound type. The patient perceived sounds as higher when she had greater control over the situation when her eyes were open and there were self-cues, and as lower when her eyes were closed and there were investigator-cues. Time-frequency analysis of electrocorticography signals during auditory naming demonstrated medial IFG activation, characterized by low-gamma band augmentation during her own vocal response. The overall evidence provides a neural substrate for altered perception of other vocal tones according to the condition context.