Functional changes in brain activity during priming in Alzheimer's disease

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Alzheimer's disease (AD) is characterized by deficits in implicit memory, including word-stem completion priming (WSCP).
• Previous lesion studies implicated the posterior neocortex in WSCP deficits observed in AD.
• The precise neural mechanisms underlying WSCP impairment in AD remain incompletely understood.

Purpose of the Study:

• To investigate the neural correlates of word-stem completion priming (WSCP) in Alzheimer's disease (AD) patients using positron emission tomography (PET).
• To compare brain activity during WSCP between AD patients and healthy older adults.

Main Methods:

• Positron emission tomography (PET) was employed to measure brain activity.
• Participants included patients with Alzheimer's disease and normal older adults.
• A word-stem completion priming task was administered during PET scanning.

Main Results:

• Alzheimer's disease patients exhibited reduced priming effects compared to normal older adults.
• Normal older adults demonstrated decreased activity in the right occipital cortex (area 19) during priming.
• AD patients showed increased activity in the right occipital cortex (area 19) during priming.

Conclusions:

• The findings provide direct evidence linking abnormal posterior neocortical function to WSCP deficits in AD.
• Altered activity patterns in the right occipital cortex during priming suggest slower neuronal shaping in AD.
• Inadequate initial stimulus processing may contribute to the observed neuronal activity differences in Alzheimer's disease.