Sex Differences in Gamma Band Functional Connectivity Between the Frontal Lobe and Cortical Areas During an Auditory Oddball Task, as Revealed by Imaginary Coherence Assessment

Toshiro Fujimotoa, *, Eiichi Okumurab, Atsushi Kodabashia, Kouzou Takeuchia, Toshiaki Otsuboa, Katsumi Nakamuraa, Kazutaka Yatsushiroa, Masaki Sekinec, Shinichiro Kamiyaa, Susumu Shimookia, Toshiyo Tamurac
a Fujimoto General Hospital, Fujimoto Medical Systems, Miyazaki, Japan
b Medical Imaging Business Department, Ricoh Company, Ltd., Ishikawa, Japan
c Osaka Electro-Communication University, Faculty of Biomedical Engineering, Osaka, Japan

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© Fujimoto et al.; Licensee Bentham Open

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (, which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at Fujimoto General Hospital, Fujimoto Medical Systems, 17-4 Hayasuzu-cho, Miyakonojo, Miyazaki 885-0055, Japan; Tel: +81-986-22-4111; Fax: +81-986-24-5129, E-mail:


We studied sex-related differences in gamma oscillation during an auditory oddball task, using magnetoencephalography and electroencephalography assessment of imaginary coherence (IC). We obtained a statistical source map of event-related desynchronization (ERD) / event-related synchronization (ERS), and compared females and males regarding ERD / ERS. Based on the results, we chose respectively seed regions for IC determinations in low (30-50 Hz), mid (50-100 Hz) and high gamma (100-150 Hz) bands. In males, ERD was increased in the left posterior cingulate cortex (CGp) at 500 ms in the low gamma band, and in the right caudal anterior cingulate cortex (cACC) at 125 ms in the mid-gamma band. ERS was increased in the left rostral anterior cingulate cortex (rACC) at 375 ms in the high gamma band. We chose the CGp, cACC and rACC as seeds, and examined IC between the seed and certain target regions using the IC map. IC changes depended on the height of the gamma frequency and the time window in the gamma band. Although IC in the mid and high gamma bands did not show sex-specific differences, IC at 30-50 Hz in males was increased between the left rACC and the frontal, orbitofrontal, inferior temporal and fusiform target regions. Increased IC in males suggested that males may acomplish the task constructively, analysingly, emotionally, and by perfoming analysis, and that information processing was more complicated in the cortico-cortical circuit. On the other hand, females showed few differences in IC. Females planned the task with general attention and economical well-balanced processing, which was explained by the higher overall functional cortical connectivity. CGp, cACC and rACC were involved in sex differences in information processing and were likely related to differences in neuroanatomy, hormones and neurotransmitter systems.

Keywords: Anterior cingulate cortex, Gamma band, Imaginary coherence, Oddball, Sex differences.