In the absence of Alzheimer’s, decreased networking between parts of the front of the brain and parts of the back of the brain cause lower performance on cognitive tests. According to a study published in the Dec. 6 issue of Neuron by Randy L. Buckner, PhD, and colleagues, degradation of white matter is responsible for decreased communication between different areas of the brain affecting the default network. The default network is responsible for functions such as remembering and planning. However, the researchers also found that the degradation of white matter affected the dorsal attention network. The dorsal attention network is primarily engaged in cognitive tasks.
The researchers used MRI techniques to, as Dr. Buckner puts it “…catch… the failure of communication in the act.” The study focused on 93 adults, 38 which were younger controls ages 18 to 34 and 55 which were 60 to 93 years old. The researchers measured correlations between the posterior cingulate/retrosplenial cortex and the medial prefrontal cortex to determine levels of functionality. The following is an excerpt of an article from Medpage Today that discusses the study:
The researchers divided the 93 adults into a young group of 38 volunteers ages 18 to 34 and an older group of 55 volunteers ages 60 to 93.
Dr. Buckner and colleagues measured functional correlations between the medial prefrontal cortex and the posterior cingulate/retrosplenial cortex, two parts of the default network that are widely separated and connected by conduits of white matter.
They found “a dramatic reduction in correlation between the two groups” that was significant on an independent samples t test at P
Using PET scans, nine members of the older group were shown to be free of amyloid deposition, a hallmark of Alzheimer’s, the researchers reported.
But they had only slightly better correlation between the two brain areas than did the older group as a whole, and it was still significantly lower than in the younger group (P
Findings were similar for the dorsal attention system, which includes brain regions used for tasks that require directed attention, the researchers said.
Interestingly, not all widely separated brain systems are impaired, the researchers said. In particular, they showed that there was no significant difference between the younger and older volunteers in correlations between elements of the visual system.
The researchers said a consequence of the lack of communication between brain regions is significantly poorer performance (P