Anyone with a loved one suffering from Alzheimer's will tell you that one of the most heartbreaking aspects of the disease is the patient's inability to recognize who you are. Now, new research is shedding light on exactly why this is, furthering our understanding of how the disease impairs perception.

There are currently more than five million people living with Alzheimer's disease in the United States, and while there's no cure in sight, our understanding of the condition is improving at an encouraging rate. Whether it's the knowledge that mimicking movements can help rehabilitate patients, or findings out that causes are more diverse than previously thought, we're learning more about the disease as time goes on.

For the new study, which was conducted by researchers at the University of Montreal, the focus was on determining exactly why patients have difficulty recognizing faces. It focused on how we're thought to perceive faces in the first place – known as holistic perception – wherein we don't look for individual features, but take in the whole picture instead.

The researchers worked with a group of Alzheimer's patients, alongside a control group of healthy subjects. The two groups were shown photographs of faces and cars, both upright and upside down. For the upside down images, the results between the two groups were similar.

However, for the upright selection of images, the rate at which the images were identified varied dramatically. The Alzheimer's patients were much slower than the healthy subjects with the facial pictures, and made considerably more mistakes. On the other hand, they didn't have the same problems with the upright cars, the recognition of which is not believed to require holistic processing.

Those results can be seen as a confirmation that our innate holistic processing abilities – specifically those related to faces – are impaired by the disease.

While the study doesn't lead directly to new treatments, it does improve our understanding of the disease. It's essentially another piece of the puzzle, and one that could, the researchers believe, help in the development of different strategies for helping patients to recognize their loved ones, such as getting them to focus more on individual facial features.

The research was published online in the Journal of Alzheimer's Disease.