Impaired spatial processing in a mouse model of fragile X syndrome

Fragile X syndrome (FXS) is the most common form of inherited intellectual impairment. The Fmr1^-/y mouse model has been previously shown to have deficits in context discrimination tasks but not in the elevated plus-maze. To further characterize this FXS mouse model and determine whether hippocampal-mediated behaviours are affected in these mice, dentate gyrus (DG)-dependent spatial processing and Cornu ammonis 1 (CA1)-dependent temporal order discrimination tasks were evaluated. In agreement with previous findings of long-term potentiation deficits in the DG of this transgenic model of FXS, the results reported here demonstrate that Fmr1^-/y mice perform poorly in the DG-dependent metric change spatial processing task. However, Fmr1^-/y mice did not present deficits in the CA1-dependent temporal order discrimination task, and were able to remember the order in which objects were presented to them to the same extent as their wild-type littermate controls. These data suggest that the previously reported subregional-specific differences in hippocampal synaptic plasticity observed in the Fmr1^-/y mouse model may manifest as selective behavioural deficits in hippocampal-dependent tasks.