Comments on: Increased neurogenesis is not (necessarily) the opposite of reduced neurogenesis http://www.functionalneurogenesis.com/blog/2010/04/increased-neurogenesis-is-not-necessarily-the-opposite-of-reduced-neurogenesis/ New neurons in the adult brain. How they work and what they're good for. Tue, 31 Aug 2010 10:03:44 -0600 http://wordpress.org/?v=2.8.5 hourly 1 By: Jason Snyder http://www.functionalneurogenesis.com/blog/2010/04/increased-neurogenesis-is-not-necessarily-the-opposite-of-reduced-neurogenesis/comment-page-1/#comment-267 Jason Snyder Fri, 18 Jun 2010 15:59:05 +0000 http://www.functionalneurogenesis.com/blog/?p=575#comment-267 Hey Carlos - I wasn't super clear there at the end - I do agree there are ways to increase neurogenesis but the key is *selectivity*. Running increases neurogenesis but it has so many other effects on the brain that you can't isolate the neurogenesis-specific benefits. Your ideas with respect to seizures bring up a good point - that greatly-increased neurogenesis could be bad. Or maybe too much neurogenesis in an unhealthy (e.g. epileptic) brain is bad (creating a U-shaped curve) but in a healthy brain has little effect (creating the sigmoidal curve shown so artistically, above). (BTW, I would argue the Jessberger paper doesn't show increased neurogenesis is detrimental - they just show that new neurons are integrating differently in the epileptic brain. This altered integration could certainly be bad but, as Jakubs 2006, speculated, it may actually be an attempt to homeostatically restore normal functioning. I feel like someone *must* have looked at seizure susceptibility in normal and neurogenesis-deficient animals...) Thanks for the ideas! Jason Hey Carlos – I wasn’t super clear there at the end – I do agree there are ways to increase neurogenesis but the key is *selectivity*. Running increases neurogenesis but it has so many other effects on the brain that you can’t isolate the neurogenesis-specific benefits.

Your ideas with respect to seizures bring up a good point – that greatly-increased neurogenesis could be bad. Or maybe too much neurogenesis in an unhealthy (e.g. epileptic) brain is bad (creating a U-shaped curve) but in a healthy brain has little effect (creating the sigmoidal curve shown so artistically, above).

(BTW, I would argue the Jessberger paper doesn’t show increased neurogenesis is detrimental – they just show that new neurons are integrating differently in the epileptic brain. This altered integration could certainly be bad but, as Jakubs 2006, speculated, it may actually be an attempt to homeostatically restore normal functioning. I feel like someone *must* have looked at seizure susceptibility in normal and neurogenesis-deficient animals…)

Thanks for the ideas!

Jason

]]> By: Carlos Fitzsimons http://www.functionalneurogenesis.com/blog/2010/04/increased-neurogenesis-is-not-necessarily-the-opposite-of-reduced-neurogenesis/comment-page-1/#comment-266 Carlos Fitzsimons Fri, 18 Jun 2010 15:25:09 +0000 http://www.functionalneurogenesis.com/blog/?p=575#comment-266 Dear Jason. I have been reading extensively this entry of yours and although I agree in the point you are trying to make (i.e. decreased neurogenesis as opposite to increased neurogenesis, both compared to basal levels) I am not sure I absolutely agree with your affirmations. First of all, there ARE means to increase neurogenesis beyond normal levels: running; and even beyond "healthy" levels (whatever that means). For instance, almost everything that induces seizures affecting the hippocampus (i.e. kainic acid) will increase neurogenesis as compared to basal levels (i.e. Jessberger S, et al., J, Neurosc., 2007) and particularly in this model it has been demonstrated that too much neurogenesis is actually deleterious to the hippocampus. All in all, I think that it would be quite safe to speculate that, to the contrary of what the press suggested, the problem is not as simple as it looks like ( is ever?) and that there is a adequate physiological level of neurogenesis that whether decreased or increased will affect its normal functions. So, one should aim to revert or correct neurogenesis (no normal, relative levels) but never to increase or decrease it (in absolute terms) . Based on this I would suggest that your model needs to adjusted to a inverted U-shaped curve. I will be very happy to hear your opinion on this Carlos Dear Jason.
I have been reading extensively this entry of yours and although I agree in the point you are trying to make (i.e. decreased neurogenesis as opposite to increased neurogenesis, both compared to basal levels) I am not sure I absolutely agree with your affirmations. First of all, there ARE means to increase neurogenesis beyond normal levels: running; and even beyond “healthy” levels (whatever that means). For instance, almost everything that induces seizures affecting the hippocampus (i.e. kainic acid) will increase neurogenesis as compared to basal levels (i.e. Jessberger S, et al., J, Neurosc., 2007) and particularly in this model it has been demonstrated that too much neurogenesis is actually deleterious to the hippocampus.
All in all, I think that it would be quite safe to speculate that, to the contrary of what the press suggested, the problem is not as simple as it looks like ( is ever?) and that there is a adequate physiological level of neurogenesis that whether decreased or increased will affect its normal functions.
So, one should aim to revert or correct neurogenesis (no normal, relative levels) but never to increase or decrease it (in absolute terms) . Based on this I would suggest that your model needs to adjusted to a inverted U-shaped curve.
I will be very happy to hear your opinion on this
Carlos

]]> By: Mary http://www.functionalneurogenesis.com/blog/2010/04/increased-neurogenesis-is-not-necessarily-the-opposite-of-reduced-neurogenesis/comment-page-1/#comment-185 Mary Sat, 24 Apr 2010 19:44:48 +0000 http://www.functionalneurogenesis.com/blog/?p=575#comment-185 I'll be including this to my listing of bookmarks. I’ll be including this to my listing of bookmarks.

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