A hypothesis in characterizing human depression is that change in the brain's basal ganglia results in a decline of motor coordination. Such a neuro-physiological change may therefore affect laryngeal control and dynamics. Under this hypothesis, toward the goal of objective monitoring of depression severity, we investigate vocal-source biomarkers for depression; specifically, source features that may relate to precision in motor control, including vocal-fold shimmer and jitter, degree of aspiration, fundamental frequency dynamics, and frequencydependence of variability and velocity of energy. We use a 35-subject database collected by Mundt et al. in which subjects were treated over a six-week period, and investigate correlation of our features with clinical (HAMD), as well as self-reported (QIDS) Total subject assessment. To explicitly address the motor aspect of depression, we compute correlations with the Psychomotor Retardation component of clinical and selfreported Total assessments. For our longitudinal database, most correlations point to statistical relationships of our vocal-source biomarkers with psychomotor activity, as well as with depression severity.

Index Terms: major depressive disorder, motor coordination, laryngeal control, vocal biomarkers