Definition of opacity for English Language Learners. : 1  the quality of a material that does not allow light to pass through it : the quality of being opaque. : 2  the quality of being difficult to understand or explain.
Research has shown that this is not true, and that brain cells can and do regenerate, especially in the areas related to learning, decision-making, visual recognition, and the way people perceive objects in space.weet. For a long time, scientists thought that it was impossible for brain cells to regenerate because they assumed that any new cells would disrupt the order of the brain.
This ability of the brain to rewire itself, grow new parts for damaged cells, and even make new cells-its plasticity, was thought to be impossible only a few years ago (4) . Brain cells, medical students were taught, were hardwired like so many computer transistors. Once they burned out, that was the end.