title: The inhibition/excitation ratio related to task-induced oscillatory modulations during a working memory task: A multtimodal-imaging study using MEG and MRS.
abstract: Detailed studies on the association between neural oscillations and the neurotransmitters gamma-aminobutyric acid (GABA) and glutamate have been performed in vitro. In addition, recent functional magnetic resonance imaging studies have characterized these neurotransmitters in task-induced deactivation processes during a working memory (WM) task. However, few studies have investigated the relationship between these neurotransmitters and task-induced oscillatory changes in the human brain. Here, using combined magnetoencephalography (MEG) and magnetic resonance spectroscopy (MRS), we investigated the modulation of GABA and glutamate + glutamine (Glx) concentrations related to task-induced oscillations in neural activity during a WM task. We first acquired resting-state MRS and MEG data from 20 healthy male volunteers using the n-back task. Time-frequency analysis was employed to determine the power induced during the encoding and retention phases in perigenual anterior cingulate cortex (pg-ACC), mid-ACC, and occipital cortex (OC). Statistical analysis showed that increased WM load was associated with task-induced oscillatory modulations (TIOMs) of the theta-gamma band relative to the zero-back condition (TIOM0B) in each volume of interest during the encoding phase of the n-back task. The task-induced oscillatory modulations in the two-back condition relative to the zero-back condition (TIOM2B-0B) were negatively correlated with the percent rate change of the correct hit rate for 2B-0B, but positively correlated with GABA/Glx. The positive correlation between TIOM2B-0B and GABA/Glx during the WM task indicates the importance of the inhibition/excitation ratio. In particular, a low inhibition/excitation ratio is essential for the efficient inhibition of irrelevant neural activity, thus producing precise task performance.
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan. Electronic address: tyuichi@gunma-u.ac.jp.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takei
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Fujihara
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Minami
authors.initials: M
authors.lastname: Tagawa
authors.affiliation: Kyushu University, Graduate School of Medicine, Department of Clinical Neurophysiology, Higashiku, Fukuoka, Japan.
authors.forename: Naruhito
authors.initials: N
authors.lastname: Hironaga
authors.affiliation: Douglas Mental Health University Institute and Department of Psychiatry, McGill University, Montreal, QC, Canada.
authors.forename: Jamie
authors.initials: J
authors.lastname: Near
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kasagi
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Motegi
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Aoyama
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Sakurai
authors.affiliation: Gunma University Faculty of Medicine, Maebashi, Gunma, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Yamaguchi
authors.affiliation: Kyushu University, Graduate School of Medicine, Department of Clinical Neurophysiology, Higashiku, Fukuoka, Japan.
authors.forename: Shozo
authors.initials: S
authors.lastname: Tobimatsu
authors.affiliation: Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Ujita
authors.affiliation: Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tsushima
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Narita
authors.affiliation: Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Fukuda
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D018698:Glutamic Acid / Q000032:analysis / Q000378:metabolism*; D005973:Glutamine / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D015225:Magnetoencephalography; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000032:analysis / Q000378:metabolism*
chemical_list: D005973:Glutamine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid
keywords: Gamma-aminobutyric acid; Glutamate; Inhibition/excitation ratio; Magnetic resonance spectroscopy; Magnetoencephalography; Task-induced deactivation