“Personality” in laboratory mice used for biomedical research: A way of understanding variability?

Abstract

The mouse, including countless lines of transgenic and knockout mice, has become the most prominent model organism in biomedical research. Behavioral characterization is often conducted in batteries of short tests on locomotion, anxiety, learning and memory, etc. In such tests, any individual differences within groups are usually considered to be disturbing variance. In order to reduce variance in experimental animal research enormous efforts of standardization have been made. While a substantial reduction of variability has been reached compared to the earlier years of experimental animal studies a considerable amount of inter-individual differences still seems to escape standardization. This effect is demonstrated and evaluated by re-analyzing data from two experiments conducted in our laboratory with inbred mice. Interestingly, behavioral patterns of individual animals seem to be correlated across context and time. In evolutionary biology, "animal personalities" have been discussed recently to comprise such stable patterns. We argue here, that nonrandom behavioral correlations across contexts and time might underlie the variability commonly found in biomedical mouse studies.

Emergence of Individuality in Genetically Identical Mice

“…Several interneuron classes, including those that express somatostatin (SOM-INs), target the dendrites of excitatory, glutamatergic pyramidal cells (3)(4)(5). SOM-INs regulate the initiation of action potential bursts generated via active currents in postsynaptic dendrites (6)(7)(8). We hypothesized that these inputs might also exert focal influence over dendritic signaling.…”

“…However, with some exceptions [(5), see also (3,6)] the emergence of experience-based individual differences within groups of genetically identical animals exposed 10 MAY 2013 VOL 340 SCIENCE www.sciencemag.org 756 REPORTS on May 9, 2013 www.sciencemag.org to the same enriched environment has rarely been addressed. We used a large group of animals and a particularly complex environment to capture the emergence of individual differences in brain and behavior over time.…”

Constraints and flexibility in mammalian social behaviour: introduction and synthesis

“…Sources of variation in individual behaviour, which form the basis for variation in social structure, have been mainly characterized by students of mechanisms and development [49]. At fertilization, the unique genetic make-up of an individual is determined by combining parental sequences of DNA, some of which have a function in shaping behavioural patterns after birth.…”

Basal anxiety during an open field test is correlated with individual differences in contextually conditioned fear in mice

“…However, individual differences in basal anxiety have not been studied in relation to conditioned fear. A previous study showed that behavioral patterns of individual animals are correlated across time and context (Lewejohann et al 2011), implying a psychological meaning to individual differences in laboratory mice with the same genetic background.…”