Altered Habituation in the Auditory Cortex in a Subgroup of Depressed Patients by Functional Magnetic Resonance Imaging

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Abstract
The aim of this study was to measure and quantify habituation effects to auditory stimulation within the auditory cortex of 11 depressed patients with major depressive disorder compared to 11 healthy subjects. Habituation was visualized by functional magnetic resonance imaging (fMRI) employing a block design (repeated stimulation with sine tones). A subgroup of patients (n = 5) presented the following abnormal habituation fMRI pattern: significantly lower activation after the first stimulation block (p = 0.05), missing characteristic signal decay to repeated acoustic stimulation and a marked undershoot after each stimulation block. This abnormal pattern may indicate functional deficits in auditory processing occurring with depression, but our results need be confirmed in a larger, more homogeneous patient group. This paradigm may be a useful tool for assessing cortical dysfunction in mood disorders.