Of course, this is by no means proof that getting high has the exact effect on humans but it's an encouraging bit of news for researchers who've previously speculated that THC and other compounds found in cannabis may help reverse certain effects of aging in the brain, like memory loss. It seems absolutely absurd that one might treat memory loss with weed, but it actually isn't. Not to get too deep into the science, but essentially our brains contain natural cannabinoids that activate certain receptors that control particular neural activity. However, they are known to deteriorate with age. Thus, the thinking behind this sort of research is that exposing the brain to "external" cannabinoids may actually mimic the effect of the naturally occurring ones, and in effect reverse this deterioration brought on by age.
When the researchers examined the brains of the elderly mice, they discovered that the ones who'd been regularly dosed with THC had sprouted neural connections in the hippocampus, the part of the brain that deals with memory, among many other important cognitive functions. In fact, they actually began to resemble the brains of the young mice who never received any THC.