Our visual memory system has a surprisingly large capacity. Quickly browse the picture library on your phone, or fast forward a movie you have watched before, and notice how the shortly presented images easily or effortlessly trigger memories. Well, my colleagues and I used this passive visual memory system to develop a test that might one day be used to diagnose Alzheimer’s disease.
The test subjects are equipped with electroencephalogram (EEG) caps to record their brain activity and display a series of images of everyday objects on the computer screen. Then they watched a series of different images, periodically interspersed with one of the images they first saw. Images are presented on the screen at a rate of three images per second (3Hz).
The pictures they showed for the first time appeared every five pictures. If the person remembers the image, the EEG reading will show a clear neural response, and after five images, another one will be displayed, and so on. By looking at the active EEG signal at this specific frequency (0.6 Hz), we can measure the strength of a person’s memory response to previously seen images.
The beauty of this test is that it measures memory passively and objectively. People don’t provide any response and don’t even need to understand the task. They just watched a series of pictures wearing EEG caps.
The task only takes two minutes. Because it is passive, it is very suitable for use with cognitively impaired people who cannot follow instructions for complex tasks.
When a person is diagnosed with Alzheimer’s disease (which is the most common form of dementia), they usually have the disease for up to 20 years. The diagnosis is obviously not early enough.
The diagnosis of Alzheimer’s disease incorporates reports from patients and their family members or caregivers about memory loss and usually involves tests performed in the clinic. These tests are not ideal because the patient’s anxiety can interfere with the results. They also require people to be able to speak and write, which makes them ineffective for some people.
We hope that our new test called Fastball provides a new tool that can bypass these biases and provide doctors and scientists with a new way to quantify changes in memory due to disease.
Our research published in the “Brain” magazine shows that compared with healthy elderly people, Alzheimer’s disease patients have a significantly lower memory response. Using only the response from a single, passive, two-minute fastball task, we can distinguish 20 Alzheimer’s disease patients from a control group of 20 healthy elderly people with an accuracy rate of 86%. When we focus on the subset of electrodes in the visual processing area, the accuracy increases to 92%.
We are also using this new technology for long-term research in patients with mild cognitive impairment. An unpublished early analysis suggests that Fastball can cause early memory impairment. We hope that this passive, objective memory measurement can predict which of these people will develop Alzheimer’s disease in the future. We hope to release our first data report by the end of 2022.
Benefits of early diagnosis
You may be wondering if anyone wants to be diagnosed before realizing they have Alzheimer’s disease? A recent survey shows that they do. Nearly three-quarters of the interviewees said that even if they have not yet developed symptoms, they still want to know if they have Alzheimer’s disease.
Read more: Now is the time to focus on preclinical dementia
The sooner people know that they are at risk of Alzheimer’s disease, the sooner they can change simple lifestyles, such as more exercise and less alcohol, to slow the progression of the disease.
And, in July 2021, the US Food and Drug Administration approved Aduhelm, which is the first drug to treat Alzheimer’s disease. Diagnosing Alzheimer’s disease earlier and more accurately may help Aduhelm and the effectiveness of future drugs. Aduhelm’s impact on cognitive function is not as obvious as its impact on the physical characteristics of Alzheimer’s disease in the brain. More sensitive cognitive markers, such as Fastball, may be able to better detect the effects of drugs on brain function.