title: Altered cortical and subcortical connectivity due to infrasound administered near the hearing threshold - Evidence from fMRI.
abstract: In the present study, the brain's response towards near- and supra-threshold infrasound (IS) stimulation (sound frequency < 20 Hz) was investigated under resting-state fMRI conditions. The study involved two consecutive sessions. In the first session, 14 healthy participants underwent a hearing threshold-as well as a categorical loudness scaling measurement in which the individual loudness perception for IS was assessed across different sound pressure levels (SPL). In the second session, these participants underwent three resting-state acquisitions, one without auditory stimulation (no-tone), one with a monaurally presented 12-Hz IS tone (near-threshold) and one with a similar tone above the individual hearing threshold corresponding to a 'medium loud' hearing sensation (supra-threshold). Data analysis mainly focused on local connectivity measures by means of regional homogeneity (ReHo), but also involved independent component analysis (ICA) to investigate inter-regional connectivity. ReHo analysis revealed significantly higher local connectivity in right superior temporal gyrus (STG) adjacent to primary auditory cortex, in anterior cingulate cortex (ACC) and, when allowing smaller cluster sizes, also in the right amygdala (rAmyg) during the near-threshold, compared to both the supra-threshold and the no-tone condition. Additional independent component analysis (ICA) revealed large-scale changes of functional connectivity, reflected in a stronger activation of the right amygdala (rAmyg) in the opposite contrast (no-tone > near-threshold) as well as the right superior frontal gyrus (rSFG) during the near-threshold condition. In summary, this study is the first to demonstrate that infrasound near the hearing threshold may induce changes of neural activity across several brain regions, some of which are known to be involved in auditory processing, while others are regarded as keyplayers in emotional and autonomic control. These findings thus allow us to speculate on how continuous exposure to (sub-)liminal IS could exert a pathogenic influence on the organism, yet further (especially longitudinal) studies are required in order to substantialize these findings.
authors.affiliation: Department of Psychiatry and Psychotherapy, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Weichenberger
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bauer
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Kühler
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Hensel
authors.affiliation: University Clinic Hamburg-Eppendorf, Clinic and Policlinic for Psychiatry and Psychotherapy, Hamburg, Germany.
authors.forename: Caroline Garcia
authors.initials: CG
authors.lastname: Forlim
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Ihlenfeld
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Ittermann
authors.affiliation: University Clinic Hamburg-Eppendorf, Clinic and Policlinic for Psychiatry and Psychotherapy, Hamburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gallinat
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Koch
authors.affiliation: University Clinic Hamburg-Eppendorf, Clinic and Policlinic for Psychiatry and Psychotherapy, Hamburg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Kühn
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D001309:Auditory Threshold; D001931:Brain Mapping; D005260:Female; D006179:Gyrus Cinguli / Q000502:physiology*; D006801:Humans; D008144:Loudness Perception; D008279:Magnetic Resonance Imaging; D008297:Male; D055815:Young Adult