Acute effects of repetitive transcranial magnetic stimulation on attentional control are related to antidepressant outcomes

Background

Repetitive transcranial magnetic stimulation (rTMS) applied over the dorsolateral prefrontal cortex (DLPFC) is a new treatment procedure that holds promise of more insight into the pathophysiology of depression because the DLPFC may play an important role in the interplay between emotional and attentional information processing. We sought to investigate whether acute neurocognitive effects of rTMS are related to antidepressant outcomes.

Methods

Between January 2005 and May 2007, we examined the effects of a single session compared with 2 weeks of rTMS over the left DLPFC on cognition and mood in therapy-resistant patients with depression. We used a crossover placebo-controlled double-blind design and differentiated rTMS treatment responders and nonresponders. We used a task-switching paradigm to measure cognitive function.

Results

After 2 weeks of high-frequency rTMS over the left DLPFC, depressive symptoms improved in more than half (53%) of our therapy-resistant population. After a single session, mood did not improve but attentional control was increased solely within our group of treatment responders.

Limitations

Our results should be interpreted as preliminary because our sample was small and because the cognitive task we used has not been tested for validity and reliability. In addition, despite minimal stimulation of the DLPFC during sham stimulation, it is possible that the stiumlation was partially active. Finally, benzodiazepines may have had impairing effects on the attentional task.

Conclusion

Cognitive reactivity after a single session of rTMS may hold promise as a predictor of beneficial treatment outcomes. Moreover, within the group of responders, attentional control appears to play an important role in the progress of mood disorders.