Abstract
Beneficial effects of repetitive transcranial magnetic stimulation (rTMS) on left dorsolateral prefrontal cortex (DLPFC) have been consistently shown for treating various neuropsychiatrical or neuropsychological disorders, but relatively little is known about its neural mechanisms. Here we conducted a randomized, double-blind, SHAM-controlled study to assess the effects of high-frequency left DLPFC rTMS on resting-state activity. Thirty-eight young healthy subjects received two sessions of either real rTMS (N = 18, 90% motor-threshold; left DLPFC at 20 Hz) or SHAM TMS (N = 20) and functional magnetic resonance imaging scan during rest in 2 days separated by 48 h. Resting-state bran activity was measured with the fractional amplitude of low-frequency fluctuation (fALFF) and functional connectivity (FC). Increased fALFF was found in rostral anterior cingulate cortex (rACC) after 20 Hz rTMS, while no changes were observed after SHAM stimulation. Using the suprathreshold rACC cluster as the seed, increased FC was found in left temporal cortex (stimulation vs. group interaction). These data suggest that high-frequency rTMS on left DLPFC enhances low-frequency resting-state brain activity in the target site and remote sites as reflected by fALFF and FC.
Highlights
Transcranial magnetic stimulation (TMS) (Barker et al, 1985) is a non-invasive neuromodulational tool that has been widely used in cognitive neuroscience research (Bolognini and Ro, 2010) as well as neuropsychological or psychiatric disease studies (Fregni and Pascual-Leone, 2007; Rossini and Rossi, 2007)
Performed functional connectivity (FC) analysis using the same preprocessed data because FC may represent a mechanism underlying the remote effects of repetitive application of TMS (rTMS) (Fox and Raichle, 2007; Fox et al, 2012; Saiote et al, 2013)
We focused on FC of any part of the brain to regions with significant rTMS
Summary
Transcranial magnetic stimulation (TMS) (Barker et al, 1985) is a non-invasive neuromodulational tool that has been widely used in cognitive neuroscience research (Bolognini and Ro, 2010) as well as neuropsychological or psychiatric disease studies (Fregni and Pascual-Leone, 2007; Rossini and Rossi, 2007). While the mechanisms underlying the long-term effects of rTMS still remain elusive, researchers have found that rTMS shares several common features with the longterm potentiation/depression (LTP/LTD) (Bliss and Lomo, 1973) of the excitatory synaptic transmission (Hoogendam et al, 2010; Pell et al, 2011) Both rTMS and LTP/LTD are sensitive to the temporal pattern of the stimulation protocol, dependent on the induced excitability changes on the preceding activation history (Abraham and Bear, 1996), and dependent on the initiation and maintenance of synaptic plasticity (such as gene and protein expression, NMDA receptor functioning). TMS effects have been considered as results of adding stochastic noise to neuronal processing (Schwarzkopf et al, 2011)
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