Center for Advanced Study Lecture, 1999Experience and Brain Plasticity:

Interpreting the significance of Basic Research for Child Rearing and Education

William T. Greenough

Collaborators:

James Eberwine, Donald Hunt, Ben A. Oostra, Patrick Willems, Frank Kooy, Jim Black

Researchers who actually Did the Work:

Ivan Jeanne Weiler, Anna Klintsova, Jeff Kleim, Frank Angenstein, Tammy Ivanco, Kathy Bates, Brian Belt, Tess Briones, Aparna Chakravarti, Chariya Christmon, Marc Cohen, Tom Comery, Robert Galvez, Aaron Grossman, Jennifer Harris, Scott Irwin, Madhuri Idupulapati, Stewart Moran, Bindu Patel, Biraju Patel, Todd Patrick, Chad Spangler, FRAXA Res. Fndn., NIMH, NICHD

Groups Emphasizing Ages 0 to 3At ZERO TO THREE, we concentrate exclusively on these miraculous first years of life - the critical period when a child undergoes the greatest human growth and development. It's also a period when you - the parent or professional - have the opportunity to make a great impact and positively influence a child's future.

Our mission here is simple: to help children best navigate their first three years of life in order to develop a solid intellectual, emotional and social foundation. For parents and professionals alike, there's always something new and exciting to be discovered! So, set aside some time to explore - and come back often and grow with us!

Summary of “Zero to Three” and “I am your Child”-John Bruer, “The Myth of the First Three Years”

Most simply stated, the argument is this: During the first three years of life in humans, there is a period of rapid synapse formation that connects nerve cells into functioning circuits. This time of rapid synapse formation is the critical period in brain development. Although the brain continues to develop after this time, it does so by losing or eliminating synapses, not by forming new ones. It is during this critical period when enriched environments can have the greatest effect on brain development. Thus the first three years provide…a unique opportunity, during which the right experiences and early childhood programs can help children build better brains.

I Am Your Child (Rob Reiner)

Since its spring launch in 1997, I Am Your Child has educated millions of parents and professionals about breakthrough new discoveries in the process of brain development. These findings reveal that the first three years of a child's life are more important for emotional and intellectual growth than previously thought. Through mass media, community mobilization, public education and policy outreach, parents and caregivers across the U.S. and around the world are learning how to make a difference in the lives of young children.

I am your child

Thanks to new technologies, including powerful brain scans, scientists are now able to form a much clearer picture of the brain’s inner workings. These technologies have allowed new insights into early development.

I am Your Child

“From birth, the brain is rapidly creating these connections. By the time she is three, your baby’s brain has formed about 1000 trillion connections--about twice as many as adults have. A baby’s brain is super-dense, and will stay that way throughout the first decade of life. Beginning at about age eleven, a child’s brain gets rid of extra connections, gradually making order out of a thick tangle of "wires." The circuitry it ends up with is more powerful and efficient.” (1999 version; certainly improved)

I am Your Child

Is this really from Brain Research?

Q: How does the brain "know" which connections to keep?

A: This is where early experience comes into play. When a connection is used repeatedly in the early years, it becomes permanent. In contrast, a connection that is not used at all, or often enough, is unlikely to survive. For example, a child who is rarely spoken to or read to in the early years may have difficulty mastering language skills later on. By the same token, a child who is rarely played with may have difficulty with social adjustment as she grows.

What are the “New Neuroscience Findings” that Led to the Original “Zero to Three” and

“I Am Your Child” Viewpoints?

* The Findings Are Not Very New

* Findings Only a Little Bit Newer Indicate that Plasticity is a Lifelong property of the Brain

Origins of the Critical or Sensitive Period Concept

Charles R. StockardHans SpemannKonrad LorenzGilbert GottliebDavid Hubel & Torsten Wiesel

…it becomes evident that the course of embryonic development need not progress in a continuous manner, but may be stopped entirely for a considerable length of time or may be decidedly reduced in rate without necessarily injuring the end result. On the other hand, it is equally well known in a general way, and even more widely believed, that when a developing egg is injured in such a manner as to cause its development to stop, it is usually incapable of resuming development at all….

-Charles R. Stockard, Am. J. Anat., 1921

As is well-known, a certain organ arises much earlier or later in the embryo than certain others. When these primary developmental changes are on the verge of taking place or when an important organ is entering its initial stage of rapid proliferation or budding, a serious interruption of the developmental progress often causes decided injuries to this particular organ, while only slight or no ill effects may be suffered by the embryo in general. Such particularly sensitive periods during development I have termed the ‘critical moments.’

-Charles R. Stockard, Am. J. Anat., 1921

Spemann & Mangold, 1924

Konrad Lorenz (O. Heinroth): Imprinting

Gilbert Gottlieb: Prehatching Acoustic Imprinting

The Developing Brain Overproduces Synapses, the Connections Between

Neurons

“New” Neuroscience Findings: Synapse Overproduction in Visual

Cortex Development –Cragg, 1975, Cat–Boothe, Greenough, Lund & Wrege, 1979, Monkey spines–Huttenlocher & Garey, 1979, Human–Rakic et al., 1986

A Framework for Understanding Critical Periods and Lifelong

Plasticity: Experience-Expectant and Experience-Dependent Development

(Black & Greenough, 1986-98)

Addition of New Neurons to the Developing and Mature Brain?

New Non-Neuronal Cells, Such as Vasculature and Glia Are Added.

The Issue is New Neurons.

Addition of New Neurons to the Developing and Mature Brain?

* Altman & Das (1965): The rat hippocampus adds neurons in adulthood

* Kaplan (1977, 1984): The rat hippocampus and cerebral cortex add neurons in adulthood

* Rakic (1985): “Limits” to neurogenesis in the (pregnant female) macaque monkey. The rat is a bad model for the primate.

Addition of New Neurons to the Developing and Mature Brain?

* Gage (1997): The mouse hippocampus adds neurons postnatally and their survival depends upon experience

* Rakic (WSJ, NYT): The (pregnant female) macaque monkey adds no new neurons postnatally. The rodent is a bad model for the primate

Addition of New Neurons to the Developing and Mature Brain?

*Gould (1997): The monkey adds new neurons to the hippocampus postnatally

* Rakic (WSJ, NYT): The (pregnant female) macaque monkey adds no new neurons postnatally. The new world monkey is a bad model for the macaque, which is an old world monkey more closely related to humans.

Addition of New Neurons to the Developing and Mature Brain?

* Gage (1998): The human hippocampus adds neurons postnatally and their survival depends upon experience

* Rakic (Nature): Let me look at the monkeys one more time. Gosh, maybe they do add neurons postnatally to the hippocampus.

Addition of New Neurons to the Developing and Mature Brain?

* Gould (1999): The Macaque monkey Cerebral Cortex adds neurons in adulthood.

* Rakic (Comment from the floor, 1999): You are using newer methods, but they may be misleading.

Addition of New Neurons to the Developing and Mature Brain?

* Does it make a difference? Are new neurons different from old neurons with new synapses?

* Clearly synapses are added in excess of the new neurons.

* Is there a “sunset law” for new neurons?

Conclusions• The brain can add synapses throughout at least much of life

• Synapse addition seems largely dependent on learning

• The brain adds non-neuronal cells throughout at least much of life, due to activity and learning

• The brain appears to add neurons throughout much of life, regulation and importance remain to be determined