Stuck in a rut: repetitive rituals of lab, zoo and farm animals a symptom of altered brain function

Animals kept in captivity exhibit stereotypic behaviour that is fundamentally similar to that seen in human conditions of autism and schizophrenia; a finding that could confound some behavioural experiments using animals, according to Dr Georgia Mason from University of Oxford speaking at the BA Festival of Science [10.50hrs 11 September 2002].

Animals in zoos, farms and laboratories are often seen gnawing repetitively, pacing back and forward or carrying out other apparently functionless behaviours. The BBSRC-funded research has enabled the Oxford scientists to link, for the first time, the stereotypic behaviour of captive bank voles (mouse-like rodents) to changes in a region of the brain known as the basal ganglia. This part of the brain is known to be responsible for organising and sequencing behaviour and plays an important role in the behaviour of autistic and schizophrenic patients, as well as being sensitive to stress.

Dr Mason said, “We found that animals with stereotypies are prone to get stuck in habitual routines. For example, voles taught to turn right in a maze for sugar were incredibly bad at stopping this behaviour when the sugar was withdrawn. We have very recently found similar results for captive bears which spend a lot of time pacing, caged blue tits and marsh tits, and colleagues in the United States have found the same results again in caged mice, and even in parrots.”

Dr Joe Garner, one of the US researchers added, “This suggests that all manner of laboratory, zoo and pet animals may be altered by captivity. In lab animals this is especially important as stereotypic mice could potentially alter the results of some research projects. We now urgently need to find out if it is really their housing which is having these effects. If it is, we need to improve it”.

Professor Julia Goodfellow, Chief Executive of BBSRC said, “This research sheds new light on why the results of some behaviour-based studies, using laboratory rodents such as mice, can be difficult to interpret and also provides a basis for considering the rational enrichment of the housing of laboratory rodents.”

The findings of this research will be used in the development of husbandry techniques for reducing cage stereotypy as well as for investigating the neural mechanisms of human clinical stereotypies caused by institutionalisation.

Although the research suggests that captivity may have profound effects on how the brain functions it does not necessarily mean that these animals are irreversibly affected. However, stereotypy might well have important implications for animal welfare and the use of laboratory rodents in behavioural experiments. Rodents are essential research tools for such experiments but often display stereotypies in standard laboratory conditions. The research suggests that rodents with stereotypies are unlikely to be good models of normal functioning, or to provide normal backgrounds for genetic or pharmacological manipulations.

Animals tend to develop stereotypies as a result of stress, the frustration caused by failed attempts to escape and a reduction in behavioural competition caused by low environmental complexity. Although scientists have know for some time that these factors influence the development of cage stereotypies a neurophysiological understanding of these behaviours has so far been lacking. High levels of “bar-mouthing” (gnawing at the cage) in the bank voles were found to be only a part of a whole suite of behavioural symptoms that include increased activity, increased rates of switching between different types of behaviour and also abnormal persistence.

FULL STATEMENT FROM PROFESSOR JULIA GOODFELLOW, CHIEF EXECUTIVE OF BBSRC:

”This paper sheds new light on why the results of some behaviour-based studies, using laboratory rodents such as mice, can be difficult to interpret. It also provides a basis for considering the rational enrichment of the housing of laboratory rodents, both for their own welfare that might be impaired by such behaviours, and to ensure that behavioural studies are not confounded by the influence of stereotypic behaviours. The research does not cast any doubt on the validity of the vast majority of studies on whole animal physiology, biochemistry and toxicology, nor even on most neurobiology studies; but it does suggest that stereotypic behaviours could influence animals` responses in some studies reliant on behavioural responses. The paper does not, on its own, demonstrate that barren cages cause increased persistence. However, this is thought to be the most likely explanation, as it has been recognised for some time that environmental enrichment affects behaviour. This research could contribute to improving the conditions of laboratory rodents.”