© Wikimedia Commons
To even the lead scientist's surprise, the study found zero evidence of such a phenomenon. Of all 59 human brains that were sliced up and analyzed, not a single sample from a person older than thirteen displayed any evidence of newly formed neurons.
The study involved a collection of human brains that were all different ages, although they (obviously) belonged to people that were recently deceased. The large scale international study used both traditional methods of analyzing brain slices, and more modern techniques using the newest possible technology.
A lot of neurogenesis was observed in brains belonging to infants and young children, but it was clear that by the age of seven, production of new neurons had begun to significantly decrease. Furthermore, no brains older than thirteen showed any signs of developing fresh neurons whatsoever, leading the scientists to conclude, much to their own disbelief, that the human brain really does stop growing and developing by the time it reaches adulthood.
It's worth noting that this study flies in the face of some circumstantial evidence from other experiments in the past - neurogenesis has been spotted in adult dog brains, and other similar studies have shown off just enough hints of neuron generation to keep scientists' hopes alive that the brain might continue to grow late into life.
All this changed when Arturo Alvarez-Buylla, the lead author on this new study, visited a colleague in China several years ago. The pair examined some human brain samples, and noted that they couldn't see any evidence of neurogenesis. This ultimately led to the study that has just been undertaken, and its unexpected results.
It's unlikely that a similar study will be undertaken any time soon - getting hold of 59 human brains that can be sliced and diced isn't easy, which is part of the reason why this study is so seminal.
This is bad news for the hopes of being able to extend human life forever - no new neurons means that the brain can't keep learning indefinitely, and deterioration over time is inevitable. People simply can't live forever and keep their metal faculties.
There's still a chance for us to achieve immortality by uploading our brains into a computer system, but even these will fail eventually. As a species, we have yet to create a computer system that won't eventually wear down and deteriorate over time.
We might have to accept that there's a limit to the amount the human consciousness is able to endure before we all, inevitably, and up losing our ongoing battle with mental oblivion.
Or maybe it's not so much the neurons, but rather the synapses (neuron-neuron and neuron-cell connections) that define learning by selective strengthening or weakening?
Reminds me of It's not the size, but how you use it.
"The adult human brain is estimated to contain from 1014 to 5 × 1014 (100–500 trillion) synapses.[1] Every cubic millimeter of cerebral cortex contains roughly a billion (short scale, i.e. 109) of them.[2] The number of synapses in the human cerebral cortex has separately been estimated at 0.15 quadrillion (150 trillion)[3]" [wikipedia]