Brain Research: Implications for Second Language Learning. ERIC Digest. Author: Genesee, Fred

There has been a longstanding interest among second and foreign language educators in research on language and the brain. Language learning is a natural phenomenon; it occurs even without intervention. By understanding how the brain learns naturally, language teachers may be better able to enhance their effectiveness in the classroom.

BRAIN DEVELOPMENT: CAN TEACHING MAKE A DIFFERENCE?

It has long been known that different regions of the brain have specialized functions. For example, the frontal lobes are involved in abstract reasoning and planning, while the posterior lobes are involved in vision. Until recently, it was believed that these specialized regions developed from a genetic blueprint that determined the structure and function of specific areas of the brain. That is, particular areas of the brain were designed for processing certain kinds of information from birth.

New evidence suggests that the brain is much more malleable than previously thought. Recent findings indicate that the specialized functions of specific regions of the brain are not fixed at birth but are shaped by experience and learning. To use a computer analogy, we now think that the young brain is like a computer with incredibly sophisticated hardwiring, but no software. The software of the brain, like the software of desktop computers, harnesses the exceptional processing capacity of the brain in the service of specialized functions, like vision, smell, and language. All individuals have to acquire or develop their own software in order to harness the processing power of the brain with which they are born.

A number of studies support this view. However, all were carried out on animals, because it is not possible to do such research with humans. Caution is called for when extrapolating these findings to humans. The studies discussed below reveal the incredible neural flexibility of the developing (and aging) brain. (See Chapter 5 in Elman et al., 1997).

Cortical tissue transplanted from its original location to a new location in the brain of young animals takes on the structure and function of its new location and not those of its original location. More specifically, neurons in the visual cortex of rodents have been transplanted to regions of the brain that are normally linked to bodily and sensory functions. The transplanted tissue comes to function like somato-sensory neurons and loses the capacity to process visual information (O'Leary & Stanfield, 1985). Likewise, if input from the eyes is rerouted from what would normally be the visual area of the brain to what is normally the auditory area of the brain, the area receiving the visual input develops the capacity to process visual and not auditory information; in other words, it is the input that determines the function of specific areas of the brain (Sur, Pallas, & Roe, 1990).

Greenenough, Black, and Wallace (1993) have shown enhanced synaptic growth in young and aging rats raised in complex environments, and Karni et al. (1995) have shown expansion of cortical involvement in performance of motor tasks following additional learning other words, the cortical map can change even in adulthood in response to enriched environmental or learning experiences.

These findings may have implications for language educators: for one thing, that teaching and teachers can make a difference in brain development, and that they shouldn't give up on older language learners.

LEARNING THROUGH CONNECTIONS

The understanding that the brain has areas of specialization has brought with it the tendency to teach in ways that reflect these specialized functions. For example, research concerning the specialized functions of the left and right hemispheres has led to left and right hemisphere teaching. Recent research suggests that such an approach does not reflect how the brain learns, nor how it functions once learning has occurred. To the contrary, "in most higher vertebrates (humans), brain systems interact together as a whole brain with the external world" (Elman et al., 1997, p. 340). Learning by the brain is about making connections within the brain and between the brain and the outside world.

What does this mean? Until recently, the idea that the neural basis for learning resided in connections between neurons remained speculation. Now, there is direct evidence that when learning occurs, neuro-chemical communication between neurons is facilitated, and less input is required to activate established connections over time. New evidence also indicates that learning creates connections between not only adjacent neurons but also between distant neurons, and that connections are made from simple circuits to complex ones and from complex circuits to simple ones.

For example, exposure to unfamiliar speech sounds is initially registered by the brain as undifferentiated neural activity. Neural activity is diffuse, because the brain has not learned the acoustic patterns that distinguish one sound from another. As exposure continues, the listener (and the brain) learns to differentiate among different sounds and even among short sequences of sounds that correspond to words or parts of words. Neural connections that reflect this learning process are formed in the auditory (temporal) cortex of the left hemisphere for most individuals. With further exposure, both the simple and complex circuits (corresponding to simple sounds and sequences of sounds) are activated at virtually the same time and more easily.

As connections are formed among adjacent neurons to form circuits, connections also begin to form with neurons in other regions of the brain that are associated with visual, tactile, and even olfactory information related to the sound of the word. These connections give the sound of the word meaning. Some of the brain sites for these other neurons are far from the neural circuits that correspond to the component sounds of the words; they include sites in other areas of the left hemisphere and even sites in the right hemisphere. The whole complex of interconnected neurons that are activated by the word is called a neural network.

The flow of neural activity is not unidirectional, from simple to complex; it also goes from complex to simple. For example, higher order neural circuits that are activated by contextual information associated with the word doggie can prime the lower order circuit associated with the sound doggie with the result that the word doggie can be retrieved with little direct input. Complex circuits can be activated at the same time as simple circuits, because the brain is receiving input from multiple external sources--auditory, visual, spatial, motor. At the same time that the auditory circuit for the word doggie is activated, the visual circuit associated with the sight of a dog is also activated. Simultaneous activation of circuits in different areas of the brain is called parallel processing.

In early stages of learning, neural circuits are activated piecemeal, incompletely, and weakly. It is like getting a glimpse of a partially exposed and very blurry photo. With more experience, practice, and exposure, the picture becomes clearer and more detailed. As exposure is repeated, less input is needed to activate the entire network. With time, activation and recognition are relatively automatic, and the learner can direct her attention to other parts of the task. This also explains why learning takes time. Time is needed to establish new neural networks and connections between networks. This suggests that the neural mechanism for learning is essentially the same as the products of learning is a process that establishes new connections among networks and the new skills or knowledge that are learned are neural circuits and networks.