Comments on the monkey club: Intermittent fasting facilitates learning

Thought again about the results you mentioned rega...

2008-01-25T16:11:00.000-05:00

Thought again about the results you mentioned regarding NR2B downregulation in cortex and striatum but not hippocampus. Could it be that increased synaptic plasticity during critical periods is crucial specifically for organizing cortical circuits, and lower levels of plasticity is necessary for function? Perhaps the hippocampus avoids the downregulation precisely because plasticity is a benefit there.

Tricky issues, fer sure. The regional variation in NMDA receptor composition profiles makes it trickier, too.

Either way, your point still stands about lower levels of NR2B maybe being a good thing outside the lab...

It appears that the NR2B subunit is the predominan...

2008-01-25T16:05:00.000-05:00

It appears that the NR2B subunit is the predominant one during neonatal development, and NR2A subunit expression rises with a certain timecourse after birth. This has led to the hypothesis that increased synaptic plasticity is important during developmental "critical periods" (mostly done in rodents).

It's possible that it's not so much the downregulation of NR2B as the associated upregulation of NR2A that's selected - perhaps not having too much plasticity is behaviorally and evolutionarily important for surviving.

That's an interesting idea, although if NR2B expre...

2008-01-25T15:26:00.000-05:00

That's an interesting idea, although if NR2B expression was fitness-neutral, there wouldn't be a reason for downregulating it.

I wasn't able to find data on NR2B expression in humans (not surprising), but in macaques, expression levels don't change with age in the hippocampus, although there is decline in the prefrontal cortex and striatum (Bai et al., 2004). It may take some work to hammer out the species differences here. Most of the primate research has been using caloric restriction, and not intermittent fasting. The emerging rodent work suggests that IF has many similarities to CR, but it will take some time to establish connections with the primate work.

Agreed about the difficulty associating increased ...

2008-01-25T15:17:00.000-05:00

Agreed about the difficulty associating increased synaptic plasticity and 'better'. Still, downregulation of NR2B may just be a consequence of living longer than we were meant to, if humans are by and large past reproductive age (and the reach of selective pressure) by the time expression levels decline.

Sounds like fun! Post any additional follow-up tho...

2008-01-25T11:21:00.000-05:00

Sounds like fun! Post any additional follow-up thoughts to this thread.

Ha, this is exactly what I'm going to cover in SP...

2008-01-25T11:20:00.000-05:00

Ha, this is exactly what I'm going to cover in SPF! Thanks for the info...