Alzheimer's, tangerine diamond neurons reveal how to help the brain

'You are like a Juke-box', sang Edoardo Bennato some time ago. Probably, in comparative biology, the possibility of being able to learn and sing ever-changing melodies in a short time would go from the instrument that animated bars and clubs in past decades to the tangerine diamond. A bird, small, fits in the palm of your hand and comes from Australia. With an almost unique gift: it can always learn new ways of singing. Exactly like a Juke-box. But this vocal learning characteristic of his is not just a curiosity, but rather a model for assessing live how much and how the little bird's brain is able to take in, learn and adapt. Think about it. Thanks to the mandarin diamond's typical neurogenesis, mysteries about the birth, migration and maturation of neurons can be unravelled, with consequent repercussions on the brain as it learns and acquires new skills. But above all, it learns to regenerate and repair itself.

And knowledge of this mechanism could, in the future, open up new prospects for counteracting the neurodegeneration of Alzheimer's disease. Giving hope for this, but we are still at the beginning, is frontier research conducted by Boston University experts on the brains of these animals, published in Current Biology (corresponding author Benjamin Scott).

The study used sophisticated techniques to explore the brain of the mandarin diamond, analysing it with a high-powered microscope. And it made it possible to understand how new neurons can make their way in and strengthen existing connections. They behave like real explorers and are able to 'dig' real invisible tunnels. Thus they enable the neurogenesis that in humans does not occur after birth. 'In songbirds, new neurons in the adult brain behave like explorers making their way through a dense jungle,' is Scott's comment in a note. 'This may help them learn new things or repair damage, but it may come at a cost to existing cells and memories: this may explain why neurogenesis seems to be a capacity that humans do not possess outside the womb. In short: exploration and the tunnels that are created can obviously create small problems.

But for the tangerine diamond they are an advantage, which humans do not have: and it is precisely this mechanism that could help us understand why we are exposed to neurodegeneration problems such as Alzheimer's disease, also due to the inability to regenerate neurons. "In this sense, the work is particularly interesting: it makes us understand how, at least in some species, neurons are able to migrate, creating tunnels that modify brain structures and connections, thus rapidly affecting plasticity," comments Antonio Uccelli, Scientific Director of the Neuroscience Mnesys Extended Partnership.

For fish, reptiles and birds, the brain can be renewed over the course of a lifetime in terms of the quantity of nerve cells. In humans, no: at birth, practically our neuronal 'endowment' is complete. So what? So from the tangerine diamond, a true champion of regeneration, important insights can be drawn for the future. It is precisely thanks to the neurons that creep into the brain tissue, creating imperceptible damage that ultimately translates into an advantage. What might these studies mean for the human nervous system? According to experts, they open up two hypotheses: the first is that our brain has evolved to limit neurogenesis after birth as a form of protection, i.e. that this stop to new nerve cells is a way of ensuring that more determined neurons cannot break into mature connections and damage memory.