A look inside the brain of rats at play

Marijke Achterberg discusses her Veni project

Researcher Marijke Achterberg received a Veni-grant last summer, and next spring she will begin her research project on the neurobiology of social play in young rats. She previously mapped out the areas of the brain that are important for social play. With this project, she aims to further explore the connections between these brain regions, and uncover the ‘play circuit’ underlying social play behaviour.

Marijke Achterberg.

Marijke Achterberg studies ‘her’ rats in Louk Vanderschuren’s lab at the Veterinary Medicine faculty. This portrait immediately makes clear that she is mesmerised by play behaviour. ‘It’s so great to see how those little guys wrestle around and chase after each other. It's the same with children; they are just fun to watch.

During her student work placement, Achterberg examined the cognitive aspect of social play. As a PhD student, she studied the neurotransmitter systems and brain regions underlying the motivation for play, the reward value and the cognitive aspects of play. ‘With this Veni-grant, I really want to take it a step further: when it comes to the play circuit – that is, the connections between the brain regions that are important for play – how does this work?’ 

Continue reading below the photograph.

Spelinitiatie bij ratten: de 'pounce'
A rat pounces on its playmate to initiate a game. Photo: Ewoud Schmidt.

A virus as a vehicle

Achterberg wants to continue her research using chemogenetics. ‘It’s a fairly new technique in which you use a virus to express a receptor in a particular brain region, or the connection between regions.’ A virus? ‘It’s a non-pathogenic virus, which we use as a vehicle that can infect brain cells.’ When that happens, the virus expresses receptors, which are only sensitive to a modified drug. With this technique, researchers can specifically manipulate the connection between two areas of the brain and, for instance, look at how the motivation to play changes when the activity of the connection is increased or decreased.

With this Veni-grant, I really want to take it a step further: how does the play circuit in the brain work? 

Marijke Achterberg
Marijke Achterberg

Achterberg and her colleagues are already able to measure how motivated a young rat is to play with a friend in the lab: ‘We make the animals press a pedal to access their playmate. First, we teach the rat that one press on the pedal means that the door will open. Once it figures that out, the rat has to perform more presses on the pedal each time.’ Until at some point it thinks: never mind. ‘That moment is called the breaking point: the maximum number of presses on the pedal that a rat is prepared to pay for one minute of access to a playmate.’

Eager to play, or ‘not right now’?

Achterberg will specifically focus on two neurotransmitters: ‘I’ll be looking at noradrenaline and dopamine, the signalling agents in the brain that we know are important for play in certain brain regions. If we manipulate the connections between these brain regions, how does this in turn affect the motivation to play? That’s what we want to find out. We’ll also be analysing the play behaviour itself. We're killing two birds with one stone: do animals play more or less, and are they more or less motivated as a result of our manipulations?’

Spelende ratten
Rats at play. Photo: Ewoud Schmidt.

Achterberg is organising her Veni project herself, but that does not mean she will be working on her own: ‘I’ll definitely be teaming up with other researchers, such as a group at UMC Utrecht that has considerable experience with chemogenetics.’ She is additionally collaborating with a pharmaceutical company that works with animals in which a specific gene has been disabled. ‘These rats have a particular genetic manipulation that also occurs in some people with autism. We know that this affects play behaviour in these rats. The question is therefore whether this technology can also be used to bring that aspect back to normal levels.'

From rat brain to child’s play

Achterberg hopes that her research will provide starting points for conducting similar research on people in the future and being able to provide children with better treatment, for example. ‘My colleagues Louk Vanderschuren and Heidi Lesscher are involved in a Dynamics of Youth project on chronically ill children and play. We know that play is important for development. Through play, children learn how they should behave in social situations later in life.' 

In the lab, Achterberg and her colleagues can study the consequences of not being able to play in rats and make direct manipulations. 'By identifying which brain regions and connections are involved, we can then make statements about questions such as: what goes wrong in a brain suffering from a particular disorder? But also: what does a healthy brain look like? We do not yet have a sufficient answer, and I can contribute to that through this research.’

Dynamics of Youth

As one of Utrecht University's four strategic themesDynamics of Youth combines excellent child research from all seven faculties.Within Dynamics of Youth, researchers from different disciplines integrate their expertise to answer crucial questions for future generations. How can we help our children develop into balanced individuals, that are able to function successfully in a rapidly changing environment? 

Further reading

Researchers Louk Vanderschuren and Corette Wierenga of Utrecht University believe playing is a social stimulus that is very important for the development of the brain and of behaviour. Together, they received a grant to further research the importance of playing.

How important is playing for the development of the brain?