Paradoxical influence of hippocampal neurogenesis on working memory

Michael D. Saxe, Gaël Malleret, Svetlana Vronskaya, Indira Mendez, A. Denise Garcia, Michael V. Sofroniew, Eric R. Kandel, and René Hen
PNAS | March 13, 2007 | vol. 104 | no. 11 | 4642-4646

To explore the function of adult hippocampal neurogenesis, we ablated cell proliferation by using two independent and complementary methods: (i) a focal hippocampal irradiation and (ii) an inducible and reversible genetic elimination of neural progenitor cells. Previous studies using these methods found a weakening of contextual fear conditioning but no change in spatial reference memory, suggesting a supportive role for neurogenesis in some, but not all, hippocampal-dependent memory tasks. In the present study, we examined hippocampal-dependent and -independent working memory using different radial maze tasks. Surprisingly, ablating neurogenesis caused an improvement of hippocampal-dependent working memory when repetitive information was presented in a single day. These findings suggest that adult-born cells in the dentate gyrus have different, and in some cases, opposite roles in distinct types of memory.

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