Early Influences on Brain Architecture - An Interview with Neuroscientist Eric Knudsen

Abstract: Early experience has a powerful and lasting influence on how the brain develops. The physical and chemical conditions that encourage the building of a strong, adaptive brain architecture are present early in life. As brains age, a number of changes lock in the ways information is processed, making it more difficult for the brain to change to other ways of dealing with information. photo of Eric Knudsen Maintaining plasticity -- keeping the brain open to change -- takes energy, and this energy is finite. The right kinds of early experiences make the best use of this energy for the benefit of both individuals and society.

Council Member Eric Knudsen, Ph.D. is the Edward C. and Amy H. Sewall Professor of Neurobiology at Stanford University. His research focuses on mechanisms of learning and strategies of information processing in both the developing and adult brain. He investigates how the capacity for learning changes with development and maturation, and the effects of early experience on brain architecture and function.

Why is a child’s early experience so important to the development of brain architecture?

Early childhood provides a unique window of opportunity that allows complex sets of experiences to shape a child’s brain architecture. The brain’s neural circuits are enabled by experience to adapt to the full range of challenges an individual will deal with throughout life.

Can stressful early experiences derail the development of the brain’s architecture?

Absolutely. The early period of development is one of both opportunity and vulnerability. During this time, the brain is very receptive and very malleable, and has the capacity to shape itself dramatically. This is the time when a child’s brain architecture responds to experiences with the environment. When those experiences are healthy, brain architecture develops in a way that anticipates living in a healthy environment, and subsequently the child is able to meet successfully the expected challenges in life.

However, if the early environment is in some way impoverished or adverse, the brain will come to expect that this is the world it will need to deal with in the future. Then it will adapt itself to that impoverished situation, which will make it less adaptive when it encounters a richer or more complex environment later. “Toxic stress” (stress caused by negative experience that is prolonged and uncontrollable) is an example of adverse early experience. Other negative experiences can include poor nutrition, lack of cognitive input, or lack of nurturing and stable social relationships. Such adverse early experiences can cause long-lasting and dysfunctional alterations in brain architecture, resulting in a brain that is not suited for operating in a healthy, complex environment.

Whether an individual’s early experiences are good or bad, those experiences will alter the connections being formed in the brain, both in terms of their chemistry and their architecture. This is important because early experience, both positive and adverse, influences the “set points” of the brain.

Could you define a “set point”?

Set points are the “optimal operating ranges” that become established in the brain.Think of a thermostat. We’re each born with a certain genetic range of capability in any given area. Early experience influences how much of that potential genetic capability we’ll have access to throughout life. If the set point for a part of the brain related to a particular ability is set correctly, which is what generally happens with normal and healthy early experience, then that brain structure can respond optimally to a wide spectrum of experiences later in life.
A correctly set thermostat is capable of maintaining an optimal temperature by activating the heater in the winter and the air conditioner in the summer. On the other hand, a brain function that ends up locked into an atypical set point, due to deprivation or exposure to toxic stress, only responds well to a narrowly defined set of atypical circumstances. The thermostat only engages the heater; it assumes it’s always winter. It’s possible to adjust the thermostat later, but only with considerable effort and by a limited amount. Here’s an example.
Children who live in abusive homes have a hard time interpreting facial expressions, except for anger. They become very good at identifying angry expressions, but tend to misidentify ambiguous expressions as “anger.” These children go on to have a higher probability of anxiety disorders and/or aggressive behavior. Their early exposure has altered the “set point” for how they operate socially in terms of interpreting social cues. They’re very adapted to operating around anger, but that “adaptation” is not helpful when they start operating in a healthier, more complex social environment.
Children who live in abusive homes have a hard time interpreting facial expressions, except for anger.

What about individuals who haven’t had appropriate early experiences? Is there still an opportunity to change the brain architecture later?

If you want to ensure that the adult brain will operate optimally in healthy environments, one of the best ways is to train the brain in a healthy environment early, when it has the greatest capacity for plasticity. Establishing healthy set points early on stabilizes physical architecture and chemical connections in a way that encourages optimal performance. Once these conditions are established, they tend to persist into adulthood.

The good news is that, even in adults, nearly all brain circuits are capable of plasticity. We know that plasticity persists throughout life, but over time, plasticity dramatically decreases. With intense effort and appropriate conditions, some circuits can show clear progress and improvement, and respond to remediation. However, this requires more effort to get results, and the results may not be optimal.

There’s still hope, but it takes more effort. One example of this is training an adult, whose first language is Japanese, to distinguish between “r” and “l” sounds. It can be done, to some extent, with a lot of specialized effort. In contrast, a young Japanese child learns to make these, and all other phonetic distinctions, easily and reliably. One principle we’ve found is that, in older brains, a greater range of plasticity can be achieved if the learning happens in small incremental steps, rather than in single, large steps. Another way to increase learning in older brains is to get the individual more engaged, more attentive to the task at hand, by making the training emotionally engaging. But the main point is that younger brains show more plasticity, so it’s best to build a strong brain architecture early.