 Depending on the frequency of stimulation, rTMS can preferentially stimulate or inhibit cortical areas. In stroke rehabilitation, for example, inhibition of the contralateral, uninvolved hemisphere by low frequency rTMS has improved movement of the affected limbs because of less aberrant inhibition of the affected hemisphere by the healthy hemisphere. The effects of rTMS has also been investigated and found to be useful in treating refractory depression and depression in Parkinsons disease. In addition, rTMS has improved naming in patients with Alzheimers disease and has improved cognitive abilities and memory in non-demented older adults. Two studies found that rTMS improved aphasia in patients with stroke. While these studies are small, a review of the literature suggests that there may be a beneficial role for rTMS in patients with chronic neurological conditions. In addition, rTMS appears to be well tolerated, with transient headaches being the most common side effect. 