Understanding the human brain-behaviour link is a challenging task. It requires mapping connections between all the neurons across the entire brain.
To understand how neurons translate information that it receives from the environment, researchers from MIT’s Picower Institute for Learning and Memory, USA, engineered a new method. They mapped the signals from the brain that translate to behaviour in soil-dwelling roundworms (c.elegans).
These neurons are also present in humans and could help determine how human behaviour works. “This study provides a global map of how the animal’s nervous system is organised to control behaviour,” said senior author Steven Flavell, Associate Professor in MIT’s Department of Brain and Cognitive Sciences, in a statement.
The soil-dwelling worms are widely used in neuroscience and behavioural experiments as they have a simple and well-defined nervous system suitable for biological research.
Wired for brain-behaviour
The way our brain operates influences our behaviour and identity. The neuronal network processes the information when we receive external signals. These neurons interact through synapses, forming a communication framework that affects our thoughts and actions. Although this was already known, researchers previously had little understanding on how the brain coordinates behaviour and the capacity of neurons to adapt and modify themselves to influence behaviour. The current study has inched closer to understanding these details.
The findings published in the journal Cell on 21 August give insights into understanding how neural circuits perform actions and behaviours even when the surrounding environment changes in other complex organisms, including humans.
Mapping the brain-behaviour link
With the help of a microscope fitted with machine learning software, the team could record flashes of signals in the worm’s brain cells whenever there was activity in them. By this, they derived an atlas of neuron activity for all behaviours of the worms like feeding, movement, egg-laying and sleeping patterns. With this, they could correlate each behaviour to different neural activities.
“These new findings will enable a more holistic understanding of how these behaviours are controlled,” said Dr Flavell in the statement.
Brain- behaviour multitaskers
The researchers found that one group of neurons could handle multiple tasks in the worms. Some neurons help the worm move at different speeds and directions, while others instruct the worm to eat or not. Interestingly, some neurons even remembered what the worm did a minute ago, indicating that past actions affect what it was doing in the present.
“It shows how the many defined nodes that make up the animal’s nervous system encode precise behavioural features and how this depends on factors like the animal’s recent experience and current state,” said Dr Flavell.
Additionally, the researchers found some neurons mixing different information to help the worm with complex movements, managing how and in which way it moves.
Brain mapping model
Scientists created a model to closely study the connections between brain activity and behaviours. Using this model, the researchers discovered that almost 60 per cent of the neurons in the worm’s brain were connected to at least one behaviour.
Later, to understand the specific role of each cell, they labelled each cell with a unique colour. This helped them to understand how different cells in the worm’s brain are linked to its actions.
Neural metamorphosis
Dr Flavell and her team triggered a different stimulus for the worms to further validate their findings. For example, they increased the temperature of the surroundings for the worms. In response, approximately 30 per cent of those neurons responsible for translating to actions changed their function, indicating that neurons could adapt to change quickly and take on new functions.
The neurons of this group are also seen in other animals, including humans. This indicates that understanding these neurons and their role in behaviour could also help in understanding changes in human behaviour. “We hope that as our colleagues study aspects of neural circuit function, they can refer to this atlas to obtain a fairly complete view of the key neurons involved,” said Dr Flavell.
