Alzheimer’s disease is known to devastate the brain. There can be severe memory loss, mood changes, and an interference with intellectual abilities—like the inability to retain new information. Alzheimer’s disease can steadily wipe out personality and interfere with daily life.

According to the Alzheimer’s Association, Alzheimer’s is the most common form of dementia. The disease accounts for 60 to 80 percent of dementia cases in the US.

In November, research professor at the Cognitive Neurology and Alzheimer’s Disease Center at Northwestern University, Changiz Geula, presented groundbreaking findings on Alzheimer’s at the Society for Neuroscience 2016 Annual Conference in San Diego. Researchers discovered that “full-blown Alzheimer’s can exist in brains of elderly people who show superior memory and cognition.” This means some people have brains that are immune to Alzheimer’s disease even when their brains show physical evidence of it.

Alzheimer’s dementia evolves when protein waste accumulates around cells creating a plaque barrier that inhibits cells from communicating with each other. Simultaneously, another protein called tau, creates tangles inside each cell, essentially strangling it. The death of cells results in the death of trillions of neurons, which help process information, movement, memory and overall cognitive function. The onset of Alzheimer’s corrodes this complex system. The discovery in the study means there are mysterious factors protecting some people’s superior memory and cognition, even with the brain changes of Alzheimer’s are present.

Geula’s team of researchers studied the brains of eight individuals older than 90 who were selected for superior memory compared to their same-age peers who had a normal memory test performance. Three of those brains qualified pathologically as having Alzheimer’s disease, despite showing superior memory when they were alive.

The Northwestern team also examined nerve cells in the hippocampus—a region critical for memory formation. Cells in this area were relatively intact in brains of elderly with evidence of Alzheimer’s pathology but with superior memory. When they studied the brains of five elderly with full-blown Alzheimer’s they found significant amounts of dead cells in the hippocampus. The comparative pattern of analysis was also found for other areas of the brain.

If scientists can find what protects some people from developing full-blown Alzheimer’s it could help those with the pathology. Scientists have been examining possibilities for a while. One study from 2000 found that injecting the waste protein, amyloid beta, into mice reduced plaque around the brain cells of mice with a transgenic model of Alzheimer’s disease.

Another study from Stanford University found that using fMRI alongside cognitive behavioral testing could help identify the onset of Alzheimer’s.

For those worried about developing the disease, getting plenty of sleep may help (focusing with age). Memory games also help. A study from 2002 found that those with superior memory had engaged parts of the hippocampus with spatial learning strategies, like mnemonic device, to create super memory pathways in the region. In the meantime, Geula says that the next step for his team will be to explore variables such as genetics, diet and environmental influences that could confer protection against Alzheimer’s.