Research Unveils Kids' Brain Adaptability to Limb Differences

The study is one of the first to undertake neuroimaging of children with upper limb difference.

It showed that the brains of children with upper limb difference (such as one hand) were specialised to help the children adapt.

The research was undertaken by experts in our Department of Psychology and the University of Cambridge.

Brain reorganisation

Our brains hold a map of the body, with different regions of the brain supporting specific body parts. In fact, multiple such maps exist, processing sensory information such as touch, temperature and pain, as well as body position.

Our understanding of the brain's ability to reorganise these maps to compensate for limb difference has so far mainly come from studies with adults.

This is partly due to how such brain imaging studies take place. Techniques like functional magnetic resonance imaging (fMRI) require participants to lie still, which is harder for children.

As a result, little is known about how, when and why these reorganisations happen in childhood.

In this study, the team used an innovative approach to carry out one of the first brain imaging studies in young children with congenital upper limb difference.

Enchanted approach

Their study included 16 children aged between five and seven years old with upper limb difference, along with 21 children with no limb difference, and two corresponding adult groups.

Firstly, the team watched how each group performed everyday tasks like opening a jar or unwrapping a sweet. This allowed them to see how participants with upper limb difference used different body parts to approach these everyday motor tasks.

Next, children spent time in an fMRI scanner. Researchers developed an immersive story of an enchanted forest and invisible butterflies to make this less daunting. This was coupled with specially designed devices worn across the body mimicking the sensation of butterfly wings.

The researchers tracked which areas of the brain map were activated in response to the 'butterfly stimulation' of different parts of the body.

Brain map adaptation

The results showed that for children born with one hand, the brain area that would typically be allocated to the 'missing' limb instead represented other parts of the body (e.g. face).

However, changes to the body maps were not confined to the hand area. Instead, the entire brain body map changed to devote more resources to help adapt and overcome challenges.

Brain plasticity

The team used computer models to understand the nature of this brain adaptation.

Traditional thinking suggests the brain has a 'use it or lose it' strategy - the more you use a limb, the more strongly it is processed by its brain area; if you stop using it, that brain area shuts down.

But researchers found something different. They showed that the brain regulates activity within sensory-motor areas through the process of 'homeostatic plasticity' - applying it to this field of study for the first time.

Homeostatic plasticity is the brain's built-in balancing system, enabling it to adjust its own activity to maintain stability.

In the case of children with upper limb difference, this process worked to adjust sensory-motor signals to adapt to the limb difference.

Adaption from an early age

One of the key things this study aimed to understand was at what age the brain adapts to limb difference.

The researchers compared the brain maps of adults and children born with limb differences, and those of limb-typical participants. 

They found that major differences between limb-typical and limb-different participants were already present in early childhood. These remained largely stable into adulthood with only a little further development. 

This suggests late-childhood experiences have a limited role in shaping the brain.