How significant to declining neurological function is the accumulation of the heavy metals aluminum and copper, compared to mercury in brain tissue?

Mercury is a hundred times worse than aluminum or copper, but those both do not belong at appreciable levels in living tissue. In very tiny quantities as catalysts for enzymes in the case of copper, there is a natural role, but aluminum is a foreign substance and is not utilized in any beneficial fashion by the body. It is largely benign in the trace quantities that inevitably are ingested with foodstuffs and even present in beverages to some degree, especially with modern packaging. Normally there is not a significant buildup within tissue to pose a problem, but this can happen and especially from man-made and extraterrestrial-made chemicals that are spewed into the environment or used in agriculture so there is an environmental exposure that leads to a buildup. This is true for mercury as well and is the reason there are ongoing warnings about ingesting certain foods like fish from ocean sources and certain waterways where there are industrial pollutants containing mercury, because it will be concentrated in the tissue of the large fish representing the predator species because these materials are concentrated increasingly up the food chain and can reach undesirable levels with too much regular ingestion by humans. Mercury is by far the most dangerous of the three and is the weapon of choice by the Extraterrestrial Alliance wanting to cause neurologic damage of the young.