Abstract
Background: Repetitive transcranial magnetic stimulation (rTMS) is a
promising tool to study and modulate brain plasticity.
Objective: Our aim was to investigate the effects of rTMS on cognitive
functions in patients with mild cognitive impairment and Alzheimer’s disease (MCI/AD) and
assess the effect of gray matter (GM) atrophy on stimulation outcomes.
Methods: Twenty MCI/AD patients participated in the proof-of-concept
controlled study. Each patient received three sessions of 10 Hz rTMS of the right inferior
frontal gyrus (IFG), the right superior temporal gyrus (STG), and the vertex (VTX, a
control stimulation site) in a randomized order. Cognitive functions were tested prior to
and immediately after each session. The GM volumetric data of patients were: 1) compared
to healthy controls (HC) using source-based morphometry; 2) correlated with rTMS-induced
cognitive improvement.
Results: The effect of the stimulated site on the difference in cognitive
scores was statistically significant for the Word part of the Stroop test (ST-W,
p = 0.012, linear mixed models). As compared to the VTX stimulation,
patients significantly improved after both IFG and STG stimulation in this cognitive
measure. MCI/AD patients had significant GM atrophy in characteristic brain regions as
compared to HC (p = 0.029, Bonferroni corrected). The amount of atrophy
correlated with the change in ST-W scores after rTMS of the STG.
Conclusion: rTMS enhanced cognitive functions in MCI/AD patients. We
demonstrated for the first time that distinct pattern of GM atrophy in MCI/AD diminishes
the cognitive effects induced by rTMS of the temporal neocortex.
