Your brain doesn't lose plasticity until you're dead. Ever hear of someone remembering a conversation they had at age 70? The neurons had to form new synapses (plasticity) for that to happen.

In my experience recall takes longer with age, and that's only if it's memorized in the first place. I think anyone over 35 can relate to this.

Much of that is simply being out of practice. At 35 you generally don't spend that much time learning new things. But, if you go back and get a masters you can get back into the swing of things.

I've been lucky enough to be in school most of my career. I'm waaaay slower at learning now at 44 than I was at 20. It often frustrates me.

Well there's always antidepressants and stimulants to help with that. In all seriousness, don't become a drug addict but if you're really worried about that there's a decent amount of research going on into improving brain plasticity so i wouldn't be surprised if there are drug treatments to "de-age" your brain in the near future.

That said, most of the "critical periods" for learning are over by the time you hit puberty and the ability to learn advanced knowledge, like the kind taught in college, doesn't decline that much with age so I wouldn't worry about it.

What can we not learn after these "critical periods for leanring"?

I had to read that first sentence a couple of times. Do you think the brain ossifies after a certain age, making you unable to learn no things?

Plasticity is the new phrenology, he doesn't really mean it, its just something ageist people signal to each other.