Deciphering a rare Alzheimer’s variant

Not every case of Alzheimer’s disease involves memory loss—at least not in the early stages. A less common and thus less well understood type of Alzheimer’s disease called posterior cortical atrophy (PCA) is marked by loss of spatial reasoning.

“That’s when you’ve lived in the same house for 30 years, but suddenly, you’re confusing which light switch does what. Or you look in the fridge for the orange juice, and even though it’s right in front of you, you can’t pick it out from the crowd of other objects,” says Carolyn Fredericks, MD, assistant professor of neurology.

While people with PCA can’t weed out such irrelevant visual information as the other items in the refrigerator, they often maintain or even strengthen their ability to interpret emotion in facial expressions. Fredericks’ ongoing research, in collaboration with Todd Constable, PhD, professor of radiology and biomedical imaging and of neurosurgery, uses fMRI to identify the parts of the brain that become active and interact with one another when people with PCA try to read faces or, for example, find an item in a refrigerator. At the same time, the researchers track tau and beta-amyloid accumulation with PET scans.

“We’ll see what areas of the brain are linked together that allow folks with PCA to do some tasks quite well despite what’s going on,” Fredericks says, “and we will see where tau is spreading [in these patients], which is something we just don’t know for this Alzheimer’s variant.”