But when it comes to aluminum, one of the most common metals in our everyday life, evidence to link it to Alzheimer's has been lacking.
"Aluminum is not a cause and certainly not the cause of Alzheimer's, at least not at the levels we're exposed to as part of our daily life," said Karlawish.
Rumors of the deadliness of aluminum have been around for some time. As the rumor-debunking Web site Snopes has noted, it has been blamed for the death of 1920's movie star Rudolph Valentino.
But the legends appear to be ahead of the facts.
"That's an old hypothesis that's not been validated," said Whitehouse.
Although aluminum doesn't appear to be a cause of Alzheimer's, that does not exonerate all heavy metals.
"Lead poisoning contributes to Alzheimer's," said Whitehouse. "Anything you do to your brain when you're a youngster that kills brain cells puts you more at risk for late-in-life dementia."
No link has ever been demonstrated between getting a flu shot and developing Alzheimer's disease.
This myth can prove particularly harmful since senior citizens -- the same people who would be most concerned about Alzheimer's -- are asked by the CDC to get a flu shot because of how likely they are to develop complications if they develop the flu.
"Everyone needs to get a flu shot, particularly people with Alzheimer's who have a higher risk of suffering from the flu if they get it," said Karlawish.
Monitoring the safety of the flu vaccine has been done because of concerns about safety raised by the first swine flu vaccine in 1976.
When the first swine flu vaccines were given to 40 million Americans back then, a few hundred people came down with Guillain-Barre Syndrome, a rare disease that affects the nerves. That contributed to some bad publicity, leading the swine flu vaccine program to end in December of that year.
While no definitive link was ever established between Guillain-Barre and the swine flu shots, doctors have carefully monitored the safety of flu vaccines and have not seen any similar problems since.
Answer: It depends
"It can be as complex or as simple as you want to make it," said Small, noting that dividing memory into short-term and long-term is simply one way to classify it.
But Small noted that memory could be divided into categories such as working memory, where you would hold information you only need now, like a phone number, and emotional memory.
Grisolia noted that in some ways, memory can be thought of in short- and long-term terms.
It may be helpful in understanding Alzheimer's, as short term memories are quickly forgotten if they don't go through the hippocampus.
"Making the bridge is where Alzheimer's gets involved," he said.
With phone numbers, for instance, "a lot of times, by the time the telephone rings, you might not even remember who you're calling," said Grisolia.
And the problems with the hippocampus often cause the memory problems associated with Alzheimer's.
"Those are the areas where Alzheimer's hits first and worst," said Grisolia. "And then the process will start to spread to other areas of the brain."
By looking at different functions of the brain, however, one could find more "types" of memory.
Another type of memory some would consider distinct, Karlawish said, is semantic memory, such as the way you remember what the word "apply" means.