The scientists at the Schepens Eye Research Institute say such brain stem cells, when activated, can transform into neurons and repair damaged brain tissue.

Earlier research by the same scientists had demonstrated that neural stem cells exist in every part of the brain, but are mostly kept silent by chemical signals from support cells known as astrocytes.

The findings from both papers should have a far-reaching impact, said Harvard Medical School Assistant Professor Dr. Dong Feng Chen, who led the study. Chen said tapping the brain¹s dormant, but intrinsic, ability to regenerate itself is the best hope for people suffering from brain-ravaging diseases such as Parkinson's or Alzheimer's disease or traumatic brain and spinal cord injuries.

The researchers' latest findings appear in the early online edition of the Proceedings of the National Academy of Science.