A team of researchers has discovered that Alzheimer's disease disrupts areas of the brain beyond those related to memory, according to a report by New Atlas citing the journal Neuroscience. Neuroscientists have categorized brain regions and systems based on function for over a century using a network approach to brain connectivity. It has been found that the cognitive impairments seen in Alzheimer's result from the failure of multiple interconnected specialized brain systems within a vast brain network. However, it remains unclear how changes in the brain network differ with the severity of dementia and whether they differ from changes in healthy brain networks during aging. Understanding these changes is crucial for identifying the causes of cognitive and brain dysfunction associated with Alzheimer's.
### Brain Dysfunctions Associated with Alzheimer's
Researchers from the University of Texas at Dallas measured the organization of functional brain networks in individuals differing in age and dementia status to determine whether there are differences. Jagan Weig, the study's corresponding researcher, stated, "It may be possible to detect some brain dysregulations associated with Alzheimer's that go beyond memory and attention very early, even during mild cognitive impairment before a diagnosis of Alzheimer's."
### Effects of Aging
The researchers also found that Alzheimer's and healthy aging are associated with distinct patterns of brain network disruption. Alzheimer's affected connectivity in both the associative networks and sensory-motor networks, while aging primarily disrupted cognitive networks. Weig commented, "In healthy aging, the changes appear largely focused on associative systems. The sensory and motor systems are generally stable. With the available brain scan data, we can calculate age-related brain differences and observe the unique changes in the severity of dementia. Through this exploration, it becomes clear that the progression of dementia is not only related to changes in associative systems but also in sensory and motor systems."
The researchers assert that their findings suggest that network interactions affected by Alzheimer's are broader than those impacted by healthy aging.
### Visual Processing and Memory
Ziu Wei Chang, the lead researcher of the study, noted that in older adults who do not exhibit cognitive impairment, interactions are primarily among brain areas performing similar functions or within brain systems. However, in patients diagnosed with Alzheimer's, the interactions between regions performing distinct functions—such as visual processing and memory—are also altered.
The changes associated with Alzheimer's in brain networks were independent of other factors typically related to the disease, such as beta-amyloid levels. This might help explain why some individuals with typical Alzheimer's pathologies, like amyloid plaques or tau tangles, remain cognitively unaffected.
Disruption in the brain network could be a novel way to describe cognitive impairment related to Alzheimer's and may provide a target for potential treatments. Weig clarified that the findings from the study offer "important evidence towards identifying the behavioral deficits most affected in the early stages of Alzheimer's and other forms of dementia," emphasizing that "as scientists continue to enhance brain network-based biomarkers for Alzheimer's, focus is being directed towards a new and unique source of information to aid in diagnosing Alzheimer's and assessing disease risk in healthy individuals."
