We all know someone who suffered from Alzheimer’s disease. It is a neurodegenerative disease that deprives a person from performing basic functions. It results in the formation of plaques on your brain, which can damage your neurons (brain cells) and cause them to lose function. Common symptoms include memory loss, reduced cognitive function, and disorientation. In advanced cases, a person can lose the ability to speak, eat, or breathe on their own and require to be tube fed and be placed on a ventilator. Another symptom is the reduced ability to know who or what familiar people or places are. The results of a recent brain-imaging study examining the activity of certain brain regions associated with familiarity recognition and recollection may indicate the reason for this loss in recognition abilities.
The study tested twelve patients displaying early-stage Alzheimer’s disease and twelve people without Alzheimer’s. They showed the subjects pictures of familiar people (children, spouses, etc.) and places (their home) and unfamiliar people and places and used functional magnetic resonance imaging (fMRI) to determine which regions of the brain were the most active while viewing these stimuli. Active parts of the brain require increased blood flow due to increased demand for oxygen, which is carried in the blood. Functional MRI measures blood flow to regions of the brain and can therefore determine activity levels of brain regions.
There are various brain regions responsible for becoming familiar with a stimulus. The posterior cingulate cortex is the region of the brain responsible for stimulus recognition. It is located at the back of the cingulate cortex, a region of the cerebral cortex (outermost part of the brain) that is found toward the center of the brain. However, that is only involved in recognition, so there needs to be additional regions of the brain for assigning value to the stimulus. These regions are primarily found within the frontal cortex, the front region of your cerebral cortex. In particular, the two most important regions are the bilateral superior frontal cortical gyrus and the right middle orbital gyrus, located in the medial frontal cortex (towards the middle of the frontal cortex). A gyrus is one of the ridges that are found on your brain. These regions are responsible for accessing and retrieving contextual information about a stimulus (what it means).
The results of the test revealed interesting similarities and differences between the two groups. When comparing Alzheimer’s patients with those without Alzheimer’s, they found no significant difference in the activity of the posterior cingulate cortex while viewing familiar stimuli. This implies that people with Alzheimer’s are still able to recognize stimuli that they are familiar with. The reason why people with Alzheimer’s may not be able to know who someone is or what a certain place is may lie within the medial frontal cortex. They found that familiar stimuli induced more activity in the bilateral superior frontal cortical gyrus and right middle orbital gyrus in people without Alzheimer’s than those with Alzheimer’s. This was due to the inability of Alzheimer’s patients to activate these regions, resulting in less access to contextual information about a stimulus.
This lead to an interesting finding: people with Alzheimer’s are able to recognize a stimulus, but they are simply unable to retrieve any information about it and hence cannot determine exactly what or who it is. This has an important clinical application for the care of people with Alzheimer’s because they are able to perform better in places and with people that they are able to recognize even if they are unable to make a connection with the place or person.
Source:
Donix, M., Jurjanz, L., Meyer, S., Amanatidis, E.C., Baeumler, D., Huebner, T., Poettrich, K., Smolka, M.N., and Holthoff, V.A. (2013). Functional imaging during recognition of personally familiar faces and places in Alzheimer’s disease. Archives of Clinical Neurophysiology, 28(1), 72-80.
