Depressed mood, index finger force and motor cortex stimulation: a transcranial magnetic stimulation (TMS) study

The present study utilized transcranial magnetic stimulation (TMS) of the motor cortex to understand basic motor processes associated with depressive symptoms independent of cognitive requirements or diagnostic category. To assess the integrity of the basic cortical-spinal-motor circuit associated with depressed mood, TMS to the motor cortex was used to initiate motor evoked potentials (MEPs) in forearm EMG and force production measured in the right (dominant) index finger. While at rest, a group with more depressive symptoms showed less force response in the index finger following stimulations compared with a group endorsing less depressive symptoms. A negative correlation between force response in the index finger at baseline (rest) following stimulation and the Beck depression inventory indicated that depressive mood symptom elevations were associated with less response to stimulations. The results argue for a greater importance placed on the relationship between depressive mood symptoms and basic motor processes.