Measuring Memory in an Alzheimer's Treatment Trial Using a Visual Search Task

Alzheimer’s Disease (AD) is characterized by episodic memory deficits attributed to damage to the hippocampal formation. AD therapies specifically targeting hippocampal function may be best evaluated through the use of selective hippocampal tasks. I used a nonverbal hippocampal-dependent target-in-scene detection task to determine if task performance shows age-related decline and/or AD-related impairments. Participants located objects (‘targets’) that appeared/disappeared in flickering natural scenes, yielding faster search times for remembered targets than for forgotten ones. AD patients took longer and required more fixations to detect targets, indicating impaired memory. Furthermore, the AD and aged populations exhibited slower pupillary responses. As part of a clinical trial, I next asked whether deep-brain stimulation of the extended hippocampal circuit would modify memory performance in patients with early AD. The double-blind treatment trial is still underway, thus treatment efficacy is yet to be evaluated, however, trial participants showed a measurable, progressive memory impairment in this task.