This blog is a way of sharing the information and resources that have helped me to recover my son Roo from an Autism Spectrum Disorder. What I have learned is to view our symptoms as the results of underlying biological cause, which can be identified and healed. I say "our symptoms" because I also have a neuro-immune disorder called Myalgic Encephalomyelitis.

And, of course, I am not a doctor (although I have been known to impersonate one while doing imaginative play with my son)- this is just our story and information that has been helpful or interesting to us. I hope it is helpful and interesting to you!

Wednesday, July 4, 2012

The Biochemistry of the "Critical Period" Concept in Neurological Development

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.