Chinese Verbal Fluency Deficiency in Temporal Lobe Epilepsy with and without Hippocampal Sclerosis: A Multiscale...

Area of Science:

• Neuroscience
• Cognitive Psychology
• Medical Imaging

Background:

• Temporal lobe epilepsy (TLE) is a neurological disorder often associated with cognitive impairments, including deficits in verbal fluency.
• Understanding the specific patterns of verbal fluency deficiency in TLE, particularly concerning hippocampal sclerosis (HS), is crucial for diagnosis and management.
• Existing verbal fluency tasks may not fully capture the nuances of cognitive function in diverse linguistic populations, such as Chinese speakers.

Purpose of the Study:

• To evaluate a Chinese character version of the phonemic verbal fluency task (VFC) in patients with TLE.
• To investigate the distinct verbal fluency deficiency patterns in TLE with hippocampal sclerosis (TLE-HS) versus TLE without hippocampal sclerosis (TLE-NHS).
• To explore the neural underpinnings of these deficits using functional magnetic resonance imaging (fMRI).

Main Methods:

• A cross-sectional study involving 30 TLE-HS patients, 28 TLE-NHS patients, and 29 healthy controls (HC).
• Participants completed the VFC task during fMRI, allowing for analysis of brain activation, deactivation, functional connectivity, and network properties in frontal and temporal regions.
• A neural network classification model was employed to differentiate TLE-HS from TLE-NHS based on functional MRI data.

Main Results:

• Both TLE-HS and TLE-NHS groups exhibited significant activation and deactivation deficiencies during the VFC task compared to controls.
• Functional connectivity, degree centrality, and community features of the anterior inferior temporal gyri were impaired in TLE-HS but retained or enhanced in TLE-NHS.
• The VFC task demonstrated strong potential for clinical application, with a neural network model achieving an area under the curve of 0.90 in diagnosing hippocampal sclerosis.

Conclusions:

• The Chinese character verbal fluency (VFC) task is a valid and clinically applicable tool for assessing phonemic verbal fluency in Chinese-speaking patients with TLE.
• Impaired functional connectivity in phonemic circuits characterizes TLE-HS, whereas enhanced connectivity in TLE-NHS suggests a compensatory mechanism for verbal searching.
• These findings highlight differential neural network alterations in TLE based on the presence or absence of hippocampal sclerosis, offering insights into TLE pathophysiology and cognitive compensation.