Claudia Hammond busts the myth that we only use 10% of our brains:
Nine-tenths of the cells in the brain are so-called glial cells. These are the support cells, the white matter, which provide physical and nutritional help for the other 10% of cells, the neurons, which make up the grey matter than does the thinking. So perhaps people heard that only 10% of the cells do the hard graft and assumed that we could harness the glial cells too. But these are different kind of cells entirely. There is no way that they could suddenly transform themselves into neurons, giving us extra brain power.