Do housing-induced changes in brain activity cause stereotypic behaviours in laboratory mice?

Area of Science:

• Neuroscience
• Animal Behavior
• Animal Welfare Science

Background:

• Abnormal repetitive stereotypic behaviours (SBs) are common in animals experiencing poor welfare, such as social isolation or barren housing.
• The precise mechanisms by which inadequate housing alters brain function to induce SBs remain unclear, with limited evidence linking environmental effects on the brain to individual SB performance.

Purpose of the Study:

• To investigate the long-term effects of housing conditions on neuronal activity in different brain regions.
• To determine if housing-induced changes in brain activity correlate with the performance of specific stereotypic behaviours (SBs) in mice.
• To explore strain-specific and individual differences in brain activity and their relationship to SB propensity.

Main Methods:

• Utilized two mouse strains with differing SB-proneness (DBA/2s; C57/BL/6s) and two SB types (route-tracing; bar-mouthing).
• Compared neuronal activity, assessed via cytochrome oxidase histochemistry, in 13 brain regions between mice housed in conventional versus enriched conditions.
• Employed statistical analyses, including model fit analyses, to identify neural correlates of SB and housing effects.

Main Results:

• Conventional housing suppressed neuronal activity in the cortex and striatum compared to enriched housing.
• DBA mice exhibited greater basal ganglia output activity than C57 mice, irrespective of housing conditions.
• Neural correlates for bar-mouthing were identified in the substantia nigra and thalamus but were independent of housing; route-tracing showed no clear neural correlates.
• Observed housing-related changes in brain activity were not congruent with individual or strain differences in SB performance.

Conclusions:

• Conventional laboratory housing can reduce cortico-striatal neuronal activity, but this effect is not directly linked to the induction of stereotypic behaviours.
• The neural underpinnings of individual and strain differences in SBs appear to stem from inherent predispositions rather than housing-induced alterations.
• Further research with enhanced statistical power is recommended to investigate potential neural correlates in specific brain regions, including the cortex, striatum, thalamus, and substantia nigra.