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Abstract #4674

Evidence for Sensitivity Adjustment in the Auditory Cortex during Audio-Visual cross-modal fMRI

Johannes Bernarding 1 , Sebastian Baecke 1 , Claus Tempelmann 2 , and Andre Brechmann 3

1 Medical Faculty, Institute for Biometry and Medical Informatics, Otto-von-Guericke University, Magdeburg, Sachsen-Anhalt, Germany, 2 Medical Faculty, Clinic for Neurology, Otto-von-Guericke University, Magdeburg, Sachsen-Anhalt, Germany, 3 Leibniz Institute for Neurobiology, Magdeburg, Sachsen-Anhalt, Germany

In a cross-modal audio-visual fMRI study an unusual linear ramp-like increase of the hemodynamic response function (HRF) was observed in the auditory cortex during isolated visual stimulation while during coupled audio-visual stimulation the well-known block-design HRF was seen. It is hypothesized that expecting coupled visual-acoustic stimuli while only an isolated visual stimulus was presented led to an decrease of the cortical sensitivity threshold thus increasing unconsciously the perception of the ambient constant scanner noise. This result may be interpreted as evidence that internal expectations can lead to strongly changed perceptions even if external stimuli remain constant.

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