Effects of Increased Spatial Complexity on Behavioural Development and Task Performance in Lister Hooded Rats
Hager R (2012) Effects of Increased Spatial Complexity on Behavioural Development and Task Performance in Lister Hooded
Rats. PLoS ONE 7(10): e47640. doi:10.1371/journal.pone.0047640
Effects of Increased Spatial Complexity on Behavioural Development and Task Performance in Lister Hooded Rats
Sophie J. Lyst 0
Katherine Davis 0
John Gigg 0
Reinmar Hager 0
Georges Chapouthier, Universite Pierre et Marie Curie, France
0 Faculty of Life Sciences, University of Manchester , Manchester , United Kingdom
Enhancing laboratory animal welfare, particularly in rodents, has been achieved through environmental enrichment in caging systems. Traditional enrichment such as adding objects has shown to impact development, reproductive and maternal performance as well as cognition. However, effects of increased spatial complexity as part of larger novel caging systems have not been investigated. While adoption of caging systems with increased spatial complexity seems uncontroversial from a welfare perspective, effects of such housing on the development and task performance of experimental animals remains unclear. In this study, we investigate differences in key behaviours and cognitive performance between Lister Hooded rats housed in traditional (single-shelf) cages ('basic') and those housed in larger cages with an additional shelf ('enriched'). We found minor differences in maternal behaviour, such as nursing and offspring development. Further, we compared task performance in females, using a hippocampus-dependent task (T-maze) and a hippocampusindependent task (Novel Object Recognition, NOR). While in the T-maze no differences in either the rate of learning or probe trial performance were found, in the NOR task females housed in enriched cages performed better than those housed in basic cages. Our results show that increased spatial complexity does not significantly affect development and maternal performance but may enhance learning in females for a non-spatial task. Increased spatial complexity does not appear to have the same effects on behaviour and development as traditional enrichment. Thus, our results suggest no effect of housing conditions on the development of most behaviours in experimental animals housed in spatially enriched caging systems.
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Funding: This work was funded by a NERC Research Fellowship NE/F013418/1. The funders had no role in study design, data collection and analysis, decision to
publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Most behavioural research is conducted in lab-housed animals
due to the significant advantages of a controlled environment.
Such laboratory animal facilities are typically designed to provide
a standardised environment where animals can be kept in good
physical health, whilst at the same time considering economic
costs. Rodents used in research are typically housed in small cages
that lack key features of their natural environment. These
conditions have been shown to impose constraints on brain
development, particularly in the hippocampus and restrict
naturally occurring behaviour, which leads to altered brain
function [1]. This, in turn, may have implications for the validity
and conclusions drawn from experimental data when using
rodents in research, especially in behavioural neuroscience [2].
Recognising the limitations of artificial housing has led to many
attempts to improve these conditions through environmental
enrichment [3]. In order to qualify as enrichment, Leach et al. [4]
suggested that any change to the housing system should increase
the frequency and diversity of positive natural behaviours,
decrease the occurrence of abnormal behaviours, maximize the
utilization of the environment and increase the animals ability to
cope with the challenges of captivity.
Commonly, environmental enrichment involves adding novel
objects to cages, along with nesting material or shelters (see
Simpson and Kelly [5] for review) but it can also be considered in
terms of the cage design. The Code of Practice for the Housing
and Care of Animals in Designated Breeding and Supplying
Establishments [6] discusses aspects of housing for rodents and
mentions environmental improvement in terms of arranging the
cage volume to create additional complexity through extra floor
space (e.g., tubes) and platforms. Earlier studies by Chamove [7]
showed that increasing the complexity of the environment within a
cage can be beneficial to animals. These studies in mice showed
that individuals raised in more complex environments were more
active and more inclined to explore novel situations. Similar
studies assessing levels of environmental enrichment have shown
that when given the choice, rodents will spend proportionately
more time in the more complex environment than the barren one,
suggesting a preference for enrichment [2], [7], [8], [9].
In an effort to enhance the welfare benefits of caging systems for
labor (...truncated)