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Linking Information Processing and Early Diagnosis of Alzheimer’s Disease

Many researchers who study the early development of mild cognitive impairment and Alzheimer’s disease focus their attention on the short-term memory problems inherent in both conditions.  However, there are other early warning signs that merit attention, and one of these is the difficulties with processing of semantic or knowledge-based information.  I read an article today that reported on a study which looked at these very abilities, published in this month’s edition of the American Journal of Psychiatry.

In a study coordinated by Dr. Terry Goldberg, professor of psychology and behavioral science at the Hofstra North Shore – LIJ School of Medicine, and director of neurocognition at the Litwin Zucker Center for Research in Alzheimer’s Disease and Memory Disorders at the Feinstein Institute for Medical Research in Manhasset, NY, researchers set out to test a person’s semantic ability to make judgments in the difference in size between two pictured objects.  They looked not only at the person’s ability to make this determination, but also how long it took them to make it.

The study included 25 patients with mild cognitive impairment, 27 with Alzheimer’s disease, and 70 with no signs of significant cognitive impairment.  Participants were asked which was larger, a key or an ant.  They then were asked to make the same judgment between an ant and a house, with researchers hypothesizing that they would take longer to make the first of the two determinations.  Results showed a very significant difference in performance between the cognitively intact participants and those with MCI and AD.  Those with cognitive deficits did in fact have greater difficulty in determining small size differences.

Researchers then showed the study participants pictures of a small ant and a big house, as opposed to a big ant and a small house.  Those participants with MCI and AD did not have significant difficulty with the first part of the task, easily determining the size differential between a small ant and a large house.  However, when the photos were incongruent, with the size of the ant and the house disproportionately altered, they had greater difficulty, either answering incorrectly or requiring a longer time to come up with a correct response.

In order to determine whether these results have any significance when it comes to everyday functioning, researchers utilized the UCSD Skills Performance Assessment Scale, a tool that is often used to identify functional impairments in persons with schizophrenia.  They reasoned that this test provides a good measure of semantic processing, with knowledge that has been acquired remotely and over many repetitions.  (In other words, do not reflect recent learning.)  According to Dr. Goldberg, this finding is highly significant because it may show us how to strengthen these semantic processing connections through training.  He also states his opinion that it is semantic memory rather than episodic memory that is causing this slower functioning in patients.  Research will be continuing on this subject, looking at whether this functioning declines as the disease progresses (among other things).

When I was reading this story, a few questions came to mind.  (These might well be answered if I read the original study.)  Firstly, the task that was used (making a comparison between two familiar objects) strikes me, as a speech-language pathologist, as accessing some abstract reasoning skills in addition to semantic processing or information acquisition.  Secondly, I didn’t see any discussion of the results for the assessment of functional impairments.  I do, however, agree that this study is very significant in that it points to other difficulties that can be encountered by persons with both mild cognitive impairment and Alzheimer’s disease.  I look forward to reading more on this matter.

You can read the original story here.

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