[10] Crusio and his collaborators found that neuroanatomical variations in the mouse hippocampus, in particular the sizes of their intra- and infrapyramidal mossy fibers (IIPMF) correlated with learning performance.

[16] When mice are exposed to unpredictable chronic mild stress (UCMS), they start exhibiting symptoms reminiscent of major depressive disorder in humans.

They showed dramatic changes in levels of aggression,[19] anxiety,[20][21] depressive-like behaviors,[20] and learning,[22] with a concomitant drop in neurogenesis.

[22] However, the results were strain- and sex-specific and there did not appear to be a clear-cut correlation between the different changes, so that they finally concluded that although their data do not disprove the idea that deficits in hippocampal neurogenesis solely underlie the behavioral impairments observed in human psychiatric disorders such as depression, they do not provide support for this hypothesis either.

This idea is based on the fact that patients suffering from the Fragile X syndrome, caused by a deficiency of the FMR1 gene often show autistic symptoms.

[27] The standards for the publication of mouse mutant studies that he and his co-editors developed for this journal[28] are gradually being accepted in the field.

[45] In 1996, Crusio was one of two co-founders of the International Behavioural and Neural Genetics Society,[46] for which he served as member-at-large of the executive committee, treasurer, and president (1998–2001).