It seems that one of the reasons that the brain may have such a folded outer surface is that it acts as its own cushion when the head suffers impact.
Today’s invention is therefore a helmet liner which consists of a resilient rubber sheet squeezed in the void between an inner and outer shell.
The sheet could be manufactured with indicative sulci and gyri crease lines moulded into it (based on where the cortex has evolved to locate these folds). This would be dropped into the outer shell, and the inner shell pressed in on top, slightly compressing the sheet itself.
There may be some applications in which the space in which the folds form could be filled with a light fluid for increased damping/cushioning.