Dementia may be caused by incomplete memories (Psychcentral)

Dementia may be caused by incomplete or partial memories — rather than by a lack of them — which creates more room for confusion, according to research from the University of Cambridge.

Current theory holds that memory problems are the result of total forgetfulness in regards to past events or objects. New findings, however, reveal that the brain’s capacity for holding complete, detailed memories is limited. The remaining less-detailed memories can become easily confused, resulting in an increased possibility for remembering false information.

“This study suggests that a major component of memory problems may actually be confusion between memories, rather than loss of memories per se,” Dr Lisa Saksida, from the Department of Experimental Psychology at the University of Cambridge.

“This is consistent with reports of memory distortions in dementia – for example, patients may not switch off the cooker, or may fail to take their medication, not because they have forgotten that they should do these things, but because they think they have already done so.”

Previous studies have shown that animals with dysfunctional memories couldn’t tell the difference between a new object and an old one. In these studies, however, scientists were unable to differentiate between whether or not the animal couldn’t distinguish the objects because it viewed the old object as being new (forgotten something that happened), or because it saw the new object as being old (false memory).

In an effort to figure out which scenario was the case, scientists devised a new method to analyze the animals’ responses to both new and old objects. Animals were exposed to an object for an hour, and then once the researchers took the object away, the animal was given a memory test by being shown either the same object again or a new object.

The results show that amnesic animals spent the same amount of time investigating the old object and the new one.  Healthy animals, however, showed more interest in the new object by exploring it longer.  To scientists, this extra interest in something new suggested that they still held a memory for the ‘old’ object.

Interestingly, the amnesic animals spent less time on the new object than did the healthy animals, a possible indication for a false memory for the new object.

In conclusion, the researchers believe that these memory difficulties resulted from the brain’s inability to form complete memories of the objects, and that the remaining, less detailed memories became more prone to confusion.

The scientists then used this information to see if they could improve an animal’s performance on the memory test if there were no other memories to puzzle the brain. For this experiment, the animals were placed in a dark, quiet environment (instead of the usual busy one) before the test.

Animals that had originally displayed poor memories after spending pre-test time in the normal, busy environment, later had perfect memories when their pre-test moments were spent in a dark and quiet environment.

“One thing that we found very surprising about our results was the extent of the memory recovery, achieved simply by reducing the incoming information prior to the memory test,” said Dr. Saksida.

“Not only does this result confound our expectations, but it also gives us a clearer understanding of the possible nature of the memory impairment underlying amnesia and certain types of dementia, which is critical to developing more sophisticated and effective treatments.”

“This also tells us something about how detrimental interference from other things can be when we are trying to remember something, an issue that may be increasingly relevant as the number of potential distractions in our daily lives seems to be on the rise.”

The researchers hope this study leads to new treatments capable of diminishing confusion between memories, possibly through the development of drugs that can enhance the intricacies required to separate memories.

“Alternatively, deliberate and intentional use of the details differentiating objects and events might be a strategy that could prolong independence and help to improve daily functioning for patients,” said Dr. Saksida.

“Even more exciting would be the ability to develop treatments that could stop the disease in the early stages, rather than treatments that address the symptoms once dementia has set in. Early detection of memory impairment is critical for the development of such treatments, and a better understanding of the nature of the impairment, as we have found here, is critical to such early detection.”

This study is published in the journal Science.

Source:  University of Cambridge

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