13 research outputs found
Altered cortical and subcortical connectivity due to infrasound administered near the hearing threshold – Evidence from fMRI
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
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ReHo results.
<p>Statistical analysis of beta values extracted from the respective clusters observed in the whole-brain contrasts.</p
Significant condition differences in resting state fMRI of the ICA.
<p>Significant condition differences in resting state fMRI of the ICA.</p
Schematic drawing of the experimental setup.
<p>Schematic drawing of the experimental setup.</p
Results of whole-brain contrast regional homogeneity (ReHo) maps acquired during near-threshold vs. no-tone condition.
<p>Higher local connectivity in: (A) Right superior temporal gyrus (rSTG) in a sagittal (left), coronal (middle) and transversal (right) slice, as well as in (B) Anterior cingulate cortex (ACC) (p < 0.001, cluster-size corrected by means of Monte Carlo simulation, k > 22). (C) Higher local connectivity in right amygdala (rAmyg) when using a more lenient cluster threshold of k > 10.</p
Box plot showing regional homogeneity (ReHo) differences across conditions.
<p>Box plot showing regional homogeneity (ReHo) differences across conditions.</p
Acoustical characterization of 14 participants according to hearing threshold and categorical loudness scaling measurements for an IS-pure tone at 12 Hz.
<p>Acoustical characterization of 14 participants according to hearing threshold and categorical loudness scaling measurements for an IS-pure tone at 12 Hz.</p