From birdsong to neurodegenerative diseases
The key role of song in shaping the brainA final point in this study: it has long been suspected that the fact of singing in itself induces the growth of the song control regions of the brain. Like athletes who build their leg muscles through exercise, by repeatedly executing a behaviour, the brain is sculpted and reshaped through the addition of new neurons and the increase in the complexity of their connections. It was known that testosterone induces a growth in volume of the song nuclei – which is associated with extremely active neurogenesis- and it was assumed that this growth resulted from a direct effect on HVC and RA. The recently published paper demonstrates that putting testosterone in the preoptic area increases the frequency of song and the size of the nuclei HVC. They practically double in volume in birds with testosterone in the preoptic area, exactly like those with systemic testosterone. The researchers further showed that the number of songs produced correlated with the size of the nuclei, observed at the end of the experiment. All this proves the vital importance of the singing activity. And in the brains of humans (who sing?...)As explained earlier, this research on the canary was not taken very seriously in the beginning. Destroying a dogma is no easy matter and Fernando Nottebohm had to conduct many studies to convince scientists that there really were new neurons added to the HVC of adult canaries. “He was able to demonstrate it”, Jacques Balthazart adds, “and as a result, researchers began to investigate the phenomenon in mammals. They realised that this was also the case in the latter, though to a lesser degree, because the canary replaces more or less 1 % of its neurons a day in this area of the brain, while humans only replace 1.75 % a year in a limited region of the brain, the hippocampus! It is not the same thing, but it still occurs. And this adult neurogenesis has an important function in problems concerning memory consolidation, reaction to stress, etc. We now believe that a certain number of treatments for depression act by modulating neurogenesis and bringing new neurons to certain areas in the brain, for instance”. |
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