Poster #: 24
Topic: Clinical applications (incl. consciousness)
Friday, Sep 11, 2015
Frontal dysfunction in patients with major depression revealed by an auditory mismatch paradigm: an fMRI investigation
Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Medical School, Aachen, Germany
In the present study we employed functional magnetic resonance imaging to identify neural mechanisms underlying auditory mismatch processing in 25 patients with major depression (MD) and 25 matched control subjects in a modified auditory mismatch paradigm. In this paradigm 30 sec long standard and deviant blocks were alternately presented within an eight minute sequence. Standard blocks comprised standard stimuli only. In deviant blocks each second stimulus deviated from the standard tone either in frequency, duration, amplitude, location, or it contained a silent gap in the middle. In both groups, blocks with deviants led to an increase of activity in the auditory cortex and a deactivation in the visual system, indicating a resource allocation to the auditory domain during mismatch processing. In MD patients, deviant blocks led to a deactivation in the rostral part of the anterior cingulate cortex (ACC) and left inferior frontal cortex. Consequently, group differences emerged only at prefrontal sites. Dysfunction of the rostral part of the ACC is a well-documented finding in MD and essentially contributes to the affective symptomatology, in particular to rumination and sadness. Deactivation of the rostral part of the ACC during the presentation of deviant blocks may thus reflect an impaired resource reallocation and shift of attention to the auditory modality. In summary, our results suggest dysfunctional resource redistribution in patients with MD but find no evidence for a deficit in early sensory processing.