Transcranial Magnetic Stimulation (TMS) has been shown to be effective in treating depression and schizophrenia , but the exact mechanisms were unknown. TMS is nomally utilized for ‘knocking off’ activity of a brain region near the skull. If this brain area serves an inhibitory function, TMS would lead to more activation in some other connected areas of the brain and vice versa.
As per this blurb from the New Scientist, Battaglia and colleagues found that repeated TMS application to mice hippocampus (dentate gyrus) over a period of 5 days lead to more stem cell neurons there and also lead to strengthening of existing synaptic connection by means of Long Term Potentiation(LTP). It should be noted that hippocampus is one of the prime areas in human brain where neurogenesis happens.
I have blogged earlier regarding the depression-as-low-neurogenesis-in-hippocampus theory and this finding seems to support that theory and provides a mediating mechanism of neurogenesis via which TMS may be leading to alleviation of depression. The researchers also believe that this finding would help in making devices that could lead to alleviation of learning and memory problems like that faced in the Alzheimer’s.