Experience-dependent changes in hippocampal spatial activity and hippocampal circuit function are disrupted in a rat model of Fragile X Syndrome.
Antonis Asiminas, Sam A Booker, Owen R Dando and 7 others
PMID 36536454WHAT IT FOUND
In a rat model of Fragile X syndrome, hippocampal neurons failed to adapt their firing patterns and spatial mapping as the environment became familiar.
This suggests a biological basis for difficulty with habituation to novelty seen in patients.
Key findings
01Wild-type rats showed a decrease in hippocampal neuron firing rate and burst probability as they became familiar with the environment, but rats with the Fragile X mutation did not show this experience-dependent adaptation.
02Wild-type rats showed increased spatial precision (higher spatial information, smaller place fields) over two days, whereas Fragile X rats failed to refine their spatial coding with experience.
03Ex vivo tests revealed that hippocampal neurons in Fragile X rats were hyperexcitable due to reduced medium afterhyperpolarization, and received weaker synaptic input from the entorhinal cortex compared to wild-type rats.
STILL TO COME
How it was doneWhat they found
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What it does not show
This is an animal study using a rat model; findings cannot be directly applied to human clinical practice. The study only covered two days of habituation; it is unclear if Fragile X rats would eventually adapt with longer exposure. The sample size was small (7 rats per group for in vivo recordings). Recordings were taken from only one section of the hippocampus (mid-proximal-distal axis), so results may not represent the whole structure.
Declared interests
The authors declare no competing interests. The study was supported by the Wellcome Trust and Medical Research Council.
The easy way to misread this
Do not interpret these neural deficits as evidence that the rats had measurable cognitive or behavioral impairments. The study reports physiological changes in the brain, not the functional behavioral outcomes in the animals.