COMPENSATORY REALLOCATION OF BRAIN RESOURCES SUPPORTING VERBAL EPISODIC MEMORY IN ALZHEIMERS-DISEASE

Conscious recall of past events that have specific temporal and spatia l contexts, termed episodic memory, is mediated by a system of interre lated brain regions. In Alzheimer's disease (AD) this system breaks do wn, resulting in an inability to recall events from the immediate past . Using subtraction techniques with PET-acquired images of regional ce rebral blood flow, we demonstrate that AD patients show a greater acti vation of regions of cerebral cortex normally involved in auditory-ver bal memory, as well as activation of cortical areas not activated by n ormal elderly subjects. These results provide clear evidence of functi onal plasticity in the AD patient's brain even if those changes do not result in normal memory function, and provide insights into the mecha nisms by which the AD brain attempts to compensate for neurodegenerati on.