Different stimulation targets of rTMS modulate specific triple-network and hippocampal-cortex functional connectivity

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Repetitive transcranial magnetic stimulation (rTMS) is a common treatment for Alzheimer's disease (AD).
• Heterogeneity in rTMS treatment targets can lead to varied outcomes.
• Understanding network-level effects is crucial for optimizing AD treatment.

Purpose of the Study:

• To investigate how different rTMS targets modulate functional connectivity (FC) in Alzheimer's disease (AD) patients.
• To examine the impact of rTMS on the hippocampus (HIP) and the triple network (salience network [SN], central executive network [CEN], default mode network [DMN]).
• To compare the effects of targeting the left dorsolateral prefrontal cortex (dlPFC) versus the bilateral angular gyrus (ANG).

Main Methods:

• 63 AD patients received rTMS targeting either the dlPFC (n=48) or ANG (n=15).
• Network-level FC was analyzed within the triple network before and after treatment.
• Voxel-level analysis used the HIP as a seed, comparing dlPFC and ANG rTMS effects.

Main Results:

• dlPFC rTMS primarily affected CEN FC; ANG rTMS primarily affected SN and DMN FC.
• Both therapies reduced FC between the right temporal lobe (DMN) and the left HIP.
• Hippocampal-cortex FC was a dominant factor in therapeutic effects, correlating with cognitive improvements.

Conclusions:

• rTMS targeting different brain regions differentially modulates specific network FC in AD.
• Both dlPFC and ANG stimulation influence hippocampal-cortex FC, impacting therapeutic outcomes.
• Stratifying AD patients by network damage can refine future rTMS treatment strategies.