Effects of Childhood Adversity on Brain Development

Global health research has previously been limited to the use of behavioural assessments to measure the effect of exposure to early socio-economic and health challenges.

A team of developmental psychologists from Birkbeck is currently carrying out a project in The Gambia, which uses portable, low-invasive, low-cost brain imaging techniques to improve understanding of the impact of adversity on early brain development.

They have also been undertaking substantial work to adapt “Western” behavioural cognitive assessments to be suitable for the population living in rural subsistence farming regions of The Gambia.

The team have now published two papers, which show that early exposure to adversity may affect how quickly 5-8 month old infants brain responses adapt to repeated stimuli and how strongly they respond to new stimuli, and that cognitive performance reduces with age and is associated with infants’ physical growth.

Two new papers, published by Birkbeck psychologists working in The Gambia at the Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine (MRCG at LSHTM), have shown the impact of early exposure to adversity on brain development.

The interdisciplinary team, which includes researchers at University College London, Kings College London, the MRCG at LSHTM, the University of Cambridge and Cambridge University Hospitals NHS Foundation Trust, have now published two papers: one looking at the association between cognitive performance, age and physical growth in the first two years of life and one looking at how the brain responds to new or familiar stimuli.

The first paper describes research conducted in 2013 – 2014 as part of an initial pilot phase of the new research collaboration. Following this groundwork, the BRIGHT (Brain Imaging for Global Health) project was established in 2015.

This project is currently following over 250 infants living in The Gambia and the UK – to track developmental trajectories of brain function and cognition across the first two years of life – using multiple measures of infant brain function, cognition, behaviour and growth as well as measures of family environment, demographics and health.

The second paper is the first to be published from the ongoing BRIGHT project.

The relationship between cognitive performance and physical growth

This study used an adapted version of the Mullen Scales of Early Learning (MSEL), a widely-used measure of child development, to examine the cognitive development of children in a rural area of The Gambia during the first two years of life and compare this with the cognitive development of US-based children. The study looked at the relationship between the MSEL scores of The Gambian children and measurements of length, weight and head circumference.

The results revealed that children from rural Gambia showed significantly lower scores than norms collected from US children from 10-14 months old. The gap between Gambian and US children then widened with increasing age, up to 24 months, which was the oldest age group included.

The gaps in the MSEL results between the two age groups appeared at different ages for different measures:

  • Differences in visual perception and motor performance were detected from age 10-14 months
  • Reduced language scores were detected from 15-19 months.

The team also found a significant association between the MSEL measures and the physical growth of the children, with slower growth being associated with lower MSEL measures.

Dr Bosiljka Milosaveljevic from Birkbeck’s Centre for Brain and Cognitive Development said: “We know that millions of children worldwide are failing to meet their cognitive potential due to environmental challenges such as poverty and undernutrition.

“There is limited knowledge of the precise nature and trajectory of compromised cognitive functions, and which are the key periods of vulnerability.

“This study builds on existing research which shows that early conditions have a significant detrimental effect on cognitive development across a range of measures. The findings could lead to interventions to counter the impact of adversity experience in early infancy and to limit the extent to which they alter neural development in rural populations in low income countries like The Gambia.”

Measuring brain development in early infancy

Due to a lack of available technologies, assessments of the impact of adversity have previously been limited to behavioural assessments in low income settings. This type of assessment has a number of limitations. Firstly, in very young infants the behaviour may be more variable or subtle, and therefore less reliable than neural measures. Secondly, some behaviours do not emerge until later childhood, even though neural markers may have been observable earlier on. And thirdly, behavioural measures have often been developed in high income settings such as the U.S. or Europe and are not yet suitable for low income countries.

The BRIGHT project is using a technique called functional near infrared spectroscopy (fNIRS), which is a portable, low invasive, low cost imaging technique, which can be used in low income settings such as The Gambia. It works by measuring the levels of oxygen change, and thus activity, in different areas of the brain, as the infant is exposed to various stimuli.

Brain responses to new and familiar stimuli

The fNIRS study measured brain activity in the participating children twice, at five and eight months.

The children listened to a voice repeating a phrase in a natural way in their first language (English for UK children and Mandinka for Gambian children). The same voice repeated the phrase and then the gender of the speaker was changed, before changing back to the first voice.

The team found that in the UK children, the brain response to the phrase being repeated by the same speaker quickly diminished as the brain recognised it as a familiar stimulus. When the voice changed to a new speaker, the brain activity increased again, recognising that this was a new stimulus.

This effect was much more visible at eight months than at five months.

In The Gambian children, the response to the same voice did not diminish as quickly as in their UK counterparts. Their brain response to a new stimulus was also diminished, showing that their brains are responding to familiar and new stimuli in a more similar way.

The results could be an indication of delayed development of attention, learning and memory mechanisms in The Gambian cohort (and therefore a lower ability to filter irrelevant information and identify new stimuli).

The team also highlight that the difference between the UK and The Gambian cohort results could be due to adaptations to very different environments. For example, the children may experience very different levels of speech directed to them, and may have different numbers of primary caregivers. In one area of The Gambia the average number of members in a family unit is 16, whereas in the UK it is 2.4. It is also possible that because of adaptations to their environments, Gambian children use a different area of the brain to detect new stimuli.

Dr Sarah Lloyd-Fox from Birkbeck’s Centre for Brain and Cognitive Development said:  “The results of this study suggest that environmental factors can affect early brain function, well before behavioural indicators emerge.

“As the BRIGHT study continues we will map individual developmental trajectories across the first two years of life and investigate links to early adversity. This will enable us to develop targeted interventions, which could avoid or limit the onset of developmental difficulties associated with adversity (such as undernutrition) at an older age.”

This article was first published in Birkbeck University Journal