Co-learning facilitates memory in mice: a new avenue in social neuroscience.

Social context affects brain function but our understanding of its neurobiology is at an early stage. The mere presence of one individual can alter the cognitive capacities of another and social learning has been demonstrated in many species, including the mouse. We asked several questions: 1. How can active engagement of two familiar mice in the same learning activity (co-learning) alter their memory? 2. Under which environmental conditions (aversive vs non-aversive) can we expect the memory to be enhanced, impaired, or not affected? 3. Can a genetic factor modify the co-learning effect on memory? More specifically, can co-learning correct memory deficits in autistic-like BTBR inbred mice with deficient sociability? We demonstrated that pairs of familiar inbred mice of the same or different genotypes (C57BL/6J and BTBR) that were habituated to new objects and their spatial location, had enhanced episodic memory in the spatial object recognition test, whereas individually-trained animals failed to solve this task. Notably, the co-learning effect was genotype-dependent. BTBR mice paired with BTBR cage-mates in the habituation session modestly ameliorated their performance in the object recognition test but co-learning with a familiar C57BL/6J mouse completely normalized episodic memory deficit. Next, we explored the co-learning effect on fear memory in these inbred strains. Interestingly, mice of both genotypes displayed significantly enhanced contextual fear memory once they had been conditioned together with BTBR animals. The same influence of BTBR presence was observed on cued fear memory in C57BL/6J mice, whereas a modest co-learning effect was found on cued fear conditioning in the BTBR strain. Taken together, we demonstrated for the first time the co-learning effect on cognitive capacities in mice, which can be modified by genetic background and environmental conditions. The possible implications of this methodological approach in social neuroscience are discussed. This article is part of a Special Issue entitled 'Cognitive Enhancers'.