A new therapy for memory loss?

Deep brain stimulation has been used in the treatment of several neurological diseases, such as essential tremor, Parkinson disease, dystonia, and oppressive compulsive disorder. But the exact mechanisms are unknown. A recent paper in Nature add a new disease to the catalogue.

Hao et al. reported that forniceal deep brain stimulation rescued hippocampal memory in Rett syndrome mice. Rett syndrome is a genetic disorder caused by MECP2 gene mutation, leading to a series of abnormalities including apraxia, seizure and intellectual disability. The authors studied the hippocampus-dependent memory in the mouse model of Rett syndrome, because memory deficits is the most reproducible measures in this model. One of the reasons that they use forniceal deep brain stimulation, though not mentioned in the beginning of the paper, might be that forniceal stimulation can enhance hippocampal memory in rodents. Thus their hypothesis is that forniceal stimulation can rescue the memory deficits in Rett syndrome mice.

The animals were divided into 4 groups: wild type sham, wild type stimulation, Rett syndrome sham, and Rett syndrome stimulation. They implanted the stimulation electrodes into the fibria-fornix, and recording electrodes into the dentate gyrus of the brain. Then mice in deep brain stimulation groups were treated with 130 Hz, 60 microsecond pulse for 1 hour a day for 14 days, and the mice in sham group were treated without pulsation. After 3 weeks, they performed the functional tests on these mice. They observed the changes of the fear memory, spatial learning and memory, long term potentiation, and neurogenesis. All these phenotypes were improved in stimulation group compared with sham group, not only for Rett syndrome mice but also for wild type mice. The results indicate that hippocampal neurogenesis are increased by foniceal deep brain stimulation, and thus the hippocampus-dependent memory is improved. More neurogenesis, better memory, like the treadmill experiments in mice once encourage people to run, is not new. And in this report, they may need to increase neurogenesis by another way to see if the memory tests in Rett syndrome brain are improved.

Although it's quite an interesting paper with some promise for neurological disorders that affect learning and memory, I am surprised that Nature accepted this paper.