The reference the author uses to support his claim in this case referred to a review he co-authored that looked at high concentrations of fluoride. Her is one funded by the National Toxicology Program both relevant to community water fluoridation concentration levels of fluoride (low): https://link.springer.com/article/10.1007/s12640-018-9870-x#... - which found, for male Long-Evans Hooded Rats at least, " Drinking water exposure at these low levels was not found to alter motor performance or learning and memory in the test paradigms assessed. Low-level F− did not alter thyroid hormone levels and produce neuronal damage or glia reactivity in the hippocampus, or histological damage in the heart, kidney, or liver. The low-level F− diet did not show a significant effect on the behavioral endpoints examined."

Why is a link to peer reviewed material getting downvoted ?

Not liking the study is one thing but downvoting a link to material without stating a reason is willful ignorance.