I don't usually do an entire post about one article, but this article in the magazine Nature, called Neurodevelopment: Unlocking the Brain warrants that. I worked as an autism therapist, and eventually ABA program director back in the 1990s before I had my own kids (yes the irony is not lost on me), and I can't underestimate how large a role the idea of critical periods in development has played in autism intervention (and the lack thereof). At that time, it was accepted as an absolute truth that there are "critical periods" during which certain types of development can happen, such as speech, and once that period comes to an end, the window is closed and a person cannot ever go back and learn that skill. For example, it was believed at that time that if a child did not begin to speak by the age of 5 they never would. This assertion was used to deny therapy to many many children. Well, I remember when families didn't give up on their kids, and kids began speaking at the age of 6, and 7, and even as late as 14 that I am aware of. As usual it takes time for the dogma of the "experts" to catch up to the observed reality "on the ground".
It turns out that the brain is far more plastic (able to adapt) then was previously thought, and this article goes into some of the "hows and whys" that are being discovered about brain development and plasticity, and what implications that may have for treatment in the future. Some of the themes discussed, such as the implications of low levels of GABA, will be familiar to many autism parents.
"What Hensch and others in the small, but rapidly advancing, field of
critical-period research are finding is that those windows can be pried
back open. “For the first time, we are beginning to understand the
biology that underlies critical periods,” says Hensch. And that
understanding is suggesting ways to intervene in various neural
disorders, including intractable conditions such as adult amblyopia, in
which information from one eye is not correctly processed by the brain,
and possibly even autism. The work could even lead to 'plasticity pills'
that enhance learning or help to wipe out traumatic memories."
“What's so interesting about Takao's work is that he has shown that even
if you miss these critical periods, you still may be able to go back in
and fix things,” says Charles Nelson, a neuroscientist at Boston
Children's Hospital, who studies the developmental effects of early
social deprivation on orphans in Romania. “The idea that you could
intervene later and make up for lost time is compelling.”
"The effect of that reduction (of GABA) was far greater than either Hensch or
Stryker had imagined: whereas control mice went through a typical
critical period and developed amblyopia when one eye was blocked, mice
with GABA deficiencies did not develop amblyopia, or have a critical
period at all. Hensch and his colleagues were able to restore plasticity
by administering a benzodiazepine, a drug that enhances the inhibitory
effect of GABA (ref. 3). Inhibition, the authors concluded, was a hidden force driving the onset
of the visual critical period. “At the time, these ideas were just so
counter-intuitive,” Hensch says. “We were turning dogma on its ear.”
"But it was unclear how the PV interneurons triggered the critical
period. An important clue came from a group led by Stryker with Arturo
Alvarez-Buylla and Sunil Gandhi, also at UCSF. The researchers
transplanted embryonic cells that were destined to become interneurons
into the brains of young mice, says Alvarez-Buylla, after which the mice
“started having two critical periods”. There was the typical critical
period, caused by the mouse's own interneurons, and then a later one, triggered when the transplanted interneurons began to mature5. The transplanted cells, says Stryker, were pushing the system's 'reset' button." (Could this be partly why stem cell therapy is effective in some kids? It's triggering the beginning of a critical period?)
There is also a lot of talk in this article about amblyopia and vision development, which is a major issue for me. I have many issues with my vision and vision processing which results in me being legally blind. According to this article, many of my issues could be the result of something that interfered with the critical period of brain development. This is interesting given that mercury is known to interrupt neurological processes and damage neurons, and is also closely associated with many vision and vision processing problems. The article also mentions that video games have been used in a particular way to treat amblyopia, because the games cause a level of concentration that may release some of the chemicals in the brain that stop the critical period and "lock" the existing patterns in, what the article refers to as "functional brakes" . Lifting those brakes can allow the brain to rewire those learned behaviors and patterns and maybe over-write dysfunctional ones.
