3 replies to this topic

[pi-]

http://en.wikipedia....erineuronal_net

 

PNNs (PeriNeuronal Nets) inhibit plasticity.  The Wikipedia page states that it is possible to enzymatically degrade PNNs. But this seems to involve injecting a substance into the brain.

 

PNNs will regrow, so it appears to be safe.

 

1. Degrading PNNs
2. Growing new brain structure through Axo/Dendro/Synapto-genesis
3. Fiddling neurotransmitter levels / tDCS / etc to optimise firing rate, LTP
4. Training with a specific learning task

 ...sounds like a good way to rewire a brain.

 

But is there any way of removing PNNs that doesn't involve injecting something into the brain?

 

pi

 

PS degrading PNNs is one of four mechanisms suggested for restoring plasticity here:  http://mathpad.wikid...om/autism-paper

Edited by pi-, 27 July 2014 - 11:53 AM.

[gsubmunu]

Dematuration appears to be induced via 5-HT4 signaling, probably via upregulation of metalloproteinases with regards to the perineuronal nets, so potent 5-HT4 receptor agonists could work:

http://www.ncbi.nlm....les/PMC2889553/

 

But this seems dangerous, IMO. Going far beyond the reduced expression of perineuronal net that SSRIs, HDACIs, AChEIs, or other potentially viable drugs already available in the clinic (with years of safety to back them) give, specifically.

First, PNN might be a candidate for some forms of long-term memory storage:

http://www.ncbi.nlm....les/PMC3725115/

PNNs also protect matured PV+ interneurons against stress, which is most likely an evolutionary essential due to their high activity and metabolic demand. In dlPFC, for example, PV+ interneurons facilitate recurrent excitation and synchronize pyramidal neurons to generate gamma oscillations necessary for working memory and information processing. In vmPFC strong competitive excitation / inhibition is part of the toolkit for decision making. Homologous “taxing” functions are found in other brain regions diverging away from elementary sensory system, and increased complexity and functionality of PV+ interneurons may directly relate to the increased cognitive abilities found in higher primates:

http://www.ncbi.nlm....les/PMC2528052/
http://www.ncbi.nlm....les/PMC2553849/

If a large quantity of human PV+ interneurons, hypothetically more sensitive to routine stressors than what is found in the rodents, are (irreversibly) damaged or even undergo cell death, it shouldn't be that safe. I would be especially concerned with neurotransmitter leeching out of previously stabilized synapse.

In addition degradation of PNNs in hippocampus has been found to be a decent animal model for schizophrenia, and numerous insults to PV+ interneurons (including reduced PNN density) are seen in schizophrenic patients, alongside their cognitive deficits and reduced frontal gamma band power.

[pi-]

@gsubmunu, thanks for that superb answer!

 

I see that you cut straight to the chase; dematuring PV+ cells, which has been shown to reopen the critical period.

 

You mention SSRIs, HDACIs, AChEIs

Have any of these been shown to reduce PNNs or demature PV+ cells?

 

It looks as though this may be a dead end in the general enquiry for reopening the critical period of plasticity.

 

pi

 

PS linking to http://www.longecity...ral-plasticity/ <-- could someone please post a reply to that thread? Anything! It's just that I can't reply to my own post until someone else does, and I want to link from it to this post.

 

 

Edited by pi-, 28 July 2014 - 05:28 PM.

[pi-]

Nooo!

 

That post got locked down and I can't edit it again :/

 

That thread in my last PS is actually posted on the wrong forum (it is in the NootStack forum, which it shouldn't be). So I subsequently posted the same enquiry in the correct forum, which is here: http://www.longecity...ral-plasticity/

 

If someone can reply to that noot-stack-forum mispost, and point it towards the correct thread, i.e. the link I just gave, I would be grateful!

 

pi