Thursday, October 4, 2007

Smelly Facts : Neuron Renewal

Have you ever heard others say that the adult brain has a fixed number of neurons and is unable to generate new ones once these die out? Indeed it was traditionally believed among scientists that the adult vertebrate brain could only lose neurons, never gain. (Kalat, 2007) Recently though, a small number of exceptions have been found. Among them, and of special interest to us of course, are the olfactory receptors. Indeed, these only tend to survive a couple of months at best, due to the fact that they constantly come into contact with harmful chemicals, as well being subjected to natural wear and tear, exposed as they are to the natural world. Thankfully, the dying olfactory receptors are constantly replaced by new developing cells! Too, adult stem cells within the brain have the ability to propagate daughter cells. These “migrate to the olfactory bulb and transform into glia cells or neurons" (Gage, 2000).

References: Graziadei & de Han, 1973, Gogos et al., 2000 and Kalat, 2007.

Image: Coronal section of olfactory bulb,


Windyridge said...

Don't your smell/taste buds deteriorate with age?

Divina said...

I hope I understand the question correctly! I will try to answer as best as I can: Both processes take place at the same time. That is, there is indeed constant renewal of cells, while at the same time the process slows down with age. It is a sad fact that everything deteriorates with age. A good example would be the collagen production.. We keep producing it, but with age we see dramatic reduction in the amount produced. And I am afraid we all know the sad consequences of that! :(

tmp00 said...

I wonder if this is responsible for your tastes maturing as you age. Several vegetables and smells that I loathed as a yoof I now love

Divina said...

That's such a good question.. I wish I had the answer - but I don't know, unfortunately. Slightly related, the reason why young children do not like most vegetables is that they taste especially bitter to them. This is an adaptive mechanism to prevent the especially vulnerable, developing young humans from consuming anything toxic/poisonous. As we grow older we learn to eat those previously disliked foods due to the fact that this increased sensitivity to bitter tastes subsides, but also by example. What you ask is much more complex though - I wish I knew what caused these changes!