Have you ever forgotten where you left your keys or forgotten the name of a common household object? If so, you may have wondered if this was a “senior moment” or just a memory lapse that could happen at any age.

A new study published this month in the journal Neuron, examined what exactly happens to the brain during these forgetful episodes, and finds that blaming your age for a bad memory doesn’t always make sense.

To understand what happens in the brain during these forgetful episodes, scientists at the University of California in Irvine used functional magnetic resonance imaging (fMRI) to analyze how the brain works when recalling information.

They analyzed 20 healthy young adults between ages 18 and 31, and 20 healthy older adults between the age of 64 and 89.

Participants were asked to complete two primary tasks. The first task involved identifying everyday objects and then distinguishing them from new ones. Thanks to the fMRI, the researchers could examine the blood flow in the brain to see which areas of the brain were utilized the most by older and younger participants during these tasks.

“Some of the images were identical to ones they’d seen before, some were brand new, and others were similar to ones they’d seen earlier, we may have changed the color or the size,” said Michael Yassa, senior author and director of University of California Irvine’s Center for the Neurobiology of Learning and Memory.

They found that older adults struggled with these subtle changes and did not do as well as younger adults in identifying new, but similar, objects in this first task.

A signal loss in the brain

In the fMRI images, the scientists could see that a region of the brain called the anterolateral entorhinal cortex may have something to do with these moments of forgetfulness in older participants.

Scientists already knew that people who suffer from Alzheimer's disease have signal loss in this region. This is important because the anterolateral entorhinal cortex communicates between two major parts of the brain, the hippocampus, where information is first encoded, and the neocortex, a portion that is involved with long-term storage.

What this small study demonstrated is that the same signaling losses in Alzheimer’s disease patients can be found in people who have aged normally. As a result, this signaling loss is one potential cause of some episodes of forgetfulness or “senior moments.”

However, further testing complicated the idea that older adults have worse memories overall.

For the study’s second task, enlisted participants had to determine if objects had changed location. In this test of spatial memory, older adults completed the test better than their younger counterparts.

From the fMRI, the team found that spatial memory is associated with a different part of the brain called the posteromedial entorhinal cortex. Their findings indicate that this area of the brain may not be impacted by aging as much as other areas.

Lead author Zachariah Reagh believes these findings suggested that “not all memory changes equally with aging.”

This means if you forget where your car keys are, it may have nothing to do with how old you are.

“This suggests that the brain-aging process is selective,” said Yassa.

As a result, in the future these findings may help indicate which patients are at risk of dementia.

“Overall this is going to end up being helpful. Right now, fMRI is not part of the standard of care in diagnosing dementia or mild cognitive impairment. It is just mostly used in research,” said Dr. Mariel Deutsch, Attending Behavioral Neurologist at the Northwell Health’s Neuroscience Institute.

How fMRI can help fight Alzheimer’s disease

While there are no treatments or ways to reverse the most common dementias, Deutsch said that this work could help researchers as they search for ways to treat diseases like Alzheimer’s.

“This study has the potential to be used as a biomarker. When you can establish what normal versus abnormal is with a test like this, you would eventually be able to test a drug that could potentially work to restore normal function,” says Deutsch. “Using an fMRI would be useful to look at brain function in real-time and this will be helpful in the future.”

Alzheimer’s is the most common type of dementia with as many as 5 million Americans living with it in 2013. This number is expected to grow to 14 million people by 2050 according to the U.S. Centers for Disease Control and Prevention.

The participating researchers hope to expand this study to better understand how memory is impacted by age. They want to enlist 150 older adults, who will be followed over time using imaging such as positron emission tomography or pet scans to look for additional pathology in the aging brain.

“It is furthering our understanding of what is a normal-aging brain versus what’s not a normal-aging brain and more specifically, it shows discrete tasks,” Deutsch said. “Eventually it could become a standard part of care in terms of diagnosing abnormal stages of cognitive dysfunction.”