CDP Journal Club: Mapping cognition along the continuum of Alzheimer’s disease

We are pleased Dr Mario Parra Rodriguez gave a presentation on novel approaches to cognitive testing at the monthly Centre for Dementia Prevention Journal Club. Dr Rodriguez talked about a shift in understanding the earliest pathological changes caused by Alzheimer’s disease and their cognitive manifestations.

The interest has shifted towards earlier detection of Alzheimer’s disease, focusing on a stage in the disease continuum where individuals do not have any symptoms but there is underlying pathology present in the brain. Currently, available tests of cognitive functions fail to detect the earliest cognitive markers indicating a risk of Alzheimer’s disease. However, recent evidence from memory studies suggests that there are subtle cognitive changes which can be detected prior to the onset of clinical symptoms and even prior to patients’ awareness of such deficits.

Dr Rodriguez presented findings from his research looking at detecting Alzheimer’s disease pathology using novel computerised technologies. His group believe that the ability to temporarily integrate object’s features in memory, a function known as short-term memory binding, appears to be impaired prior to the onset of clinical symptoms. This is true whether people are developing Alzheimer’s disease due to gene mutations, known as familial Alzheimer’s disease, or late in life in the absence of gene mutations, known as sporadic Alzheimer’s disease.

Patients who hold high risk of Alzheimer’s disease, such as those who notice that they are experiencing problems with their memory but have no apparent cognitive decline and those with cognitive decline but no indication of dementia yet, show short-term memory binding impairments. Such impairments seem to predict future development of dementia. Interestingly, neuroanatomical studies have revealed that short-term memory binding deficits in Alzheimer’s disease are not due to damage to the hippocampus, a structure long thought as the earliest seat of Alzheimer’s disease pathology and responsible for the earliest memory impairments in Alzheimer’s disease.

Dr Rodriguez and his colleagues have found short-term memory binding deficits in stages of Alzheimer’s disease where hippocampal functions remain preserved. Such evidence challenges long standing theories of memory decline during Alzheimer’s disease and calls for a reconsideration of cognitive changes and their assessment in the continuum of the disease.