Mouse Model Provides More Insight into Impaired Spacial Processing in Fragile X Syndrome

Ashraf Malhas, PhD avatar

by Ashraf Malhas, PhD |

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The association between structural abnormalities in certain regions of the brain and the ability to process spacial positioning of objects has been demonstrated in a mouse model of fragile X syndrome.

The study, “Impaired spatial processing in a mouse model of fragile X syndrome,” was published in the journal Behavioural Brain Research.

Abnormal processing of information pertaining to space and time by fragile X patients leads to cognitive abnormalities that ultimately result in intellectual impairments.

Spacial and temporal awareness is achieved by several parts of the brain working in close combination, including the dentate gyrus (DG) and Cornu ammonis 1 (CA1) — both located in the hippocampus area of the brain, which is involved in short- and long-term memory formation and in spatial memory that enables navigation.

Defects in nerve connections within these brain regions are thought to play important roles in the behavioral abnormalities observed in fragile X syndrome.

A fragile x mouse model (called the Fmr1-/y mouse) exhibits deficits in context discrimination and new object recognition tasks, along with abnormalities in nerve connections within its brain.

Researchers used two laboratory tests designed to assess spacial and temporal discrimination in both Fmr1-/y and control mice.

The first tested the animals’ ability to recognize changes in the positioning of objects within a confined space, i.e., spacial processing, which is DG-dependent. The second tested the animals’ abilities to recall objects’ positions over time, i.e., temporal processing, which is CA1-dependent.

Fmr1-/y mice had impaired spacial processing and used different space exploration strategies compared with control mice. However, there were no significant differences observed in temporal processing between Fmr1-/y and controls.

According to the researchers, Fmr1-/y mice “display deficits in a DG-dependent task involving the detection of changes in spatial relationships, but perform normally in the CA1- dependent temporal order discrimination task.”

“Since intellectual impairments observed in FXS [fragile X syndrome] patients are thought to arise from deficits in spatial and temporal processing, the findings reported here provide insight into the extent of these deficits in the Fmr1-/y mouse model of FXS,” they conclude.