Word reading and posterior temporal dysfunction in amnestic mild cognitive impairment

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Mild cognitive impairment (MCI) is a prodromal stage of Alzheimer's disease.
• Understanding language processing deficits in MCI is crucial for early diagnosis and intervention.
• Functional magnetic resonance imaging (fMRI) and chronometric analysis offer insights into brain function and dysfunction.

Purpose of the Study:

• To investigate whether the brain system for associative-semantic judgments is affected in amnestic MCI.
• To examine the relationship between these judgments and off-line chronometric analysis of word reading and picture naming.
• To identify specific brain regions involved in lexical-semantic retrieval in MCI.

Main Methods:

• fMRI was used to measure brain activity in 13 patients with amnestic MCI and 13 matched controls.
• Participants performed associative-semantic judgment tasks with words and pictures.
• Chronometric analysis of word reading and picture naming was conducted.

Main Results:

• A significant group-by-task interaction was observed in the lower bank of the posterior left superior temporal sulcus (STS).
• Controls showed word-specific activation in this region, which was significantly reduced in MCI patients.
• Reduced activation in the left posterior STS correlated strongly with impaired word reading performance.

Conclusions:

• The lower bank of the left posterior STS plays a critical role in mapping word form to word meaning (lexical-semantic retrieval).
• Impaired lexical-semantic retrieval is a key feature of language dysfunction in amnestic MCI.
• These findings contribute to understanding the neural basis of cognitive decline in Alzheimer's disease pathogenesis.