second that emotion

Emotional stimulation and early brain development

Despite the high profile of research on infant brain development, no studies of normal babies have yet shown that variations in early experiences have any effect on early brain development. Jay Belsky hopes to change this.

Professor Jay Belsky, Chair of Psychology at Birkbeck College, London, is looking for pearls. "Most of the people who study early brain development in humans have not been interested in individual differences. They have been assessing, for example, whether seven-month-old babies respond to stimuli to which five-month-old babies don’t respond. Any individual differences within these groups would be experimental ‘noise’, or errors of measurement. My hunch is that these experimentalists may be eating the oysters and throwing away the pearls. If we can establish that individual differences are systematically related to a child’s experience, then we have a pearl."

Professor Belsky has been awarded a project grant to study the possible linkages between the emotional attributes of mothers and emotion processing in babies. The key question is whether the degree of emotional (affective) stimulation that babies receive has any long-term impact on their emotion-processing abilities.

Infant brain development has become what Professor Belsky calls a ‘superhot’ topic in recent years - the Clintons hosted a White House conference on the issue in 1997 - but theories about the role of experience in shaping brain development go back a long way. Professor Belsky’s own interest has its roots in what is known as Bowlby’s attachment theory. In the late 1960s John Bowlby argued that early experiences shape a child’s attachment or sense of security by affecting the child’s ‘internal working model’. Bowlby defined this internal model as an affective-cognitive information-processing filter. "This," says Professor Belsky, "is a vital but ultimately hypothetical construct. What I am looking for is the instantiation of Bowlby’s theory - is this information-processing filter ‘hard-wired’ into the brain by infant experience?"

Animal learning

Professor Belsky also draws on the classic studies on rat brain development by, amongst others, Donald Hebb, Mark Rosenzweig and William Greenough. Fifty years ago Hebb, a Canadian psychologist, found that rats that had been reared in his house as his children’s pets were much better at learning to run mazes than their laboratory-reared littermates. Starting in the 1960s, Mark Rosenzweig and colleagues at Berkeley began to publish their findings that rats raised in enriched, more stimulating environments - ‘rat playschool’ as Professor Belsky calls it - had heavier brains and thicker cortices in certain brain regions. And, in the early 1970s, William Greenough and his colleagues at the University of Illinois began an ongoing research programme on how rearing conditions affect brain structure in rats. They raised baby rats from 30 days in either complex, social or isolated environments. At 55 days they examined the brains of the complex-environment rats, and found 20 per cent more dendritic area in certain regions of the brain - an indirect measure of the number of synapses on each neuron. Like Hebb’s rats, the complex-environment rats not only had more synapses, but also learned to run mazes more quickly.

The third strand of research informing Professor Belsky’s study is Richard Davidson’s and Nathan Fox’s work showing that babies process positive and negative emotional stimuli in different parts of the brain. Specifically, the left hemisphere of the brain is responsive to positive stimuli and the right is responsive to negative stimuli. Additionally, infants who are temperamentally more negative are more reactive (as indexed by brain measurements) to negative stimuli, while the reverse is true of infants who are temperamentally more positively disposed.

Testing positive

Professor Belsky has taken this brain research and related it back to Bowlby’s attachment theory. "Imagine we have an infant with lots of positive emotional experience. We know that positive experience is registered in different parts of the brain. And we know that experience affects the development of synapses. So do we have a situation akin to the rats’ enriched environment - except we are talking about emotional (affective) rather than learning (cognitive) development? Do we have a child who becomes, as a result of his particular experiences, especially responsive to positive experiences? Similarly, if we have a child with lots of negative experience, does it follow that the negative part of the brain becomes more developed? What we are trying to evaluate is whether, in the same way that physical exercise builds up muscles, exposure to certain emotional experiences builds up certain ‘brain muscles’."

Professor Belsky and colleagues’ research is designed specifically to test the hypothesis that variation in early experience contributes to individual differences in the processing of positive and negative facial expressions. They will be testing seven-month-old babies whose mothers score relatively high or low on the Positive and Negative Affect Scale (PANAS), a standard measure that assesses both transient mood and underlying emotion-related personality traits. There is extensive research linking maternal personality and mood with maternal behaviour towards babies. Professor Belsky and colleagues therefore reason that the test infants will already have been exposed to either positive or negative facial expressions that correlate with their mothers’ PANAS scores.

In order to examine brain function in response to facial stimuli, the researchers will be recording event-related potentials (ERPs) while the babies view images of positive and negative facial expressions. ERPs are transient changes in brain activity that occur in response to discrete events (for example, the presentation of a face on a computer screen). The timing of the various deflections in the ERP recording can provide information about the speed of processing and the distribution of voltages across the scalp at a particular time, thereby providing spatial information about the brain regions active at that moment. ERP measures are accurate to one-thousandth of a second, and so allow very precise readings of differences in speed of brain processing.

The ability to make such precise measurements of infant brain activity will be the key to these experiments. "One of the reasons I came to Birkbeck in July last year was because Mark Johnson, an expert in measuring brain function in infants, was here. I bring to the table research on family relationships, child interaction and attachment theory - a lot of thinking about psychological development. Mark knows about brain development and assessment. So along with my other collaborator, Michelle de Haan, we can now ask what turns out to be a cutting-edge question."

Recording activity

The researchers will record ERPs while infants are shown positive (happy), negative (fearful) and neutral facial expressions. Differences in ERP timings or amplitudes will reveal differences in how strongly or quickly the babies’ attention is drawn to the happy and fearful faces, and also in how familiar the happy and fearful faces are. Previous studies show that these differences do reflect processing of information in the face ‘as a face’, as they are not observed if the images of the face are presented upside down. If Professor Belsky’s hypothesis is correct, an infant whose mother scores relatively low on positive affect and high on negative affect on the PANAS will respond more to the negative facial expressions. Babies whose mothers show the reverse emotional profile should respond more to the positive facial expressions.

This initial study does not control for heritability, so if a correlation between positive and negative stimulation and brain processing is found, it will not be possible to distinguish between an inherited and an experience-dependent effect. A further study is thus planned, in which experimenters will manipulate the infants’ emotional experience by engaging them in 30 minutes of positive-emotion-eliciting play, three times a week for 16 weeks. A control group will be engaged in similar activities, but with the experimenters conveying neutral emotions.

Professor Belsky postulates that the experimental babies would show greater recognition of the happy faces than the control group. But he is sanguine about the possible results. "To use a geological metaphor, we are test drilling. We have reason to believe there may be something there - our expectation is based on good research and reasonable hypotheses. But it’s not a certainty. But then that, as far as I am concerned, is science at its best - an intellectual risk-taking venture!"

Should the data conform to Professor Belsky and Dr de Haan’s hypotheses, it will lend credence to the widespread, but still empirically unsubstantiated view that early experiences shape child development and behaviour by shaping brain functioning. It is, of course, arguments such as this that are the foundation for many social policies that emphasise intervening in the first years of life, including Sure Start in the UK and Early Head Start in the USA.

External links

Sure Start : Working with parents and children to promote the physical, intellectual and social development of pre-school children
Early Head Start : Supporting the healthy development of infants, toddlers, and their families, and pregnant women.
Professor Jay Belsky at Birkbeck College, London