Previous experiments have found that individuals with Alzheimer's disease (AD) show increased activity in prefrontal regions compared with healthy age-matched controls during cognitive tasks. This has been interpreted as compensatory reallocation of cognitive resources, but direct evidence for a facilitating effect on performance has been lacking. To address this we measured neural activity during semantic and episodic memory tasks in mildly demented AD patients and healthy elderly controls. Controls recruited a left hemisphere network of regions, including prefrontal and temporal cortices in both the semantic and episodic tasks. Patients engaged a unique network involving bilateral dorsolateral prefrontal and posterior cortices. Critically, activity in this network of regions was correlated with better performance on both the semantic and episodic tasks in the patients. This provides the most direct evidence to date that AD patients can use additional neural resources in prefrontal cortex, presumably those mediating executive functions, to compensate for losses attributable to the degenerative process of the disease.
|Number of pages||8|
|Journal||The Journal of Neuroscience|
|Publication status||Published - 2003|
Bibliographical noteCopyright the Author(s) 2003. Originally published as Grady, CL, McIntosh, AR, Beig, S., Keightley, ML, Burianova, H. & Black, SE. (2003). Evidence from functional neuroimaging of a compensatory prefrontal network in Alzheimers disease. The Journal of Neuroscience, 23(3), 986-993, http://www.jneurosci.org/content/23/3/986.full.pdf+html. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
- semantic memory
- episodic memory
- positron emission tomography
- frontal lobe