Abstract
The study assumed that the antisaccade (AS) task is a relevant psychophysical tool to assess (i) short-term neuromodulation of the dorsolateral prefrontal cortex (DLPFC) induced by intermittent theta burst stimulation (iTBS); and (ii) mood change occurring during the course of the treatment. Saccadic inhibition is known to strongly involve the DLPFC, whose neuromodulation with iTBS requires less stimulation time and lower stimulation intensity, as well as results in longer aftereffects than the conventional repetitive transcranial magnetic stimulation (rTMS). Active or sham iTBS was applied every day for 3 weeks over the left DLPFC of 12 drug-resistant bipolar depressed patients. To assess the iTBS-induced short-term neuromodulation, the saccadic task was performed just before (S1) and just after (S2) the iTBS session, the first day of each week. Mood was evaluated through Montgomery and Asberg Depression Rating Scale (MADRS) scores and the difference in scores between the beginning and the end of treatment was correlated with AS performance change between these two periods. As expected, only patients from the active group improved their performance from S1 to S2 and mood improvement was significantly correlated with AS performance improvement. In addition, the AS task also discriminated depressive bipolar patients from healthy control subjects. Therefore, the AS task could be a relevant and useful tool for clinicians to assess if the Transcranial magnetic stimulation (TMS)-induced short-term neuromodulation of the DLPFC occurs as well as a “trait vs. state” objective marker of depressive mood disorder.
Highlights
RTMS TREATMENT OF DEPRESSION: NECESSITY TO ASSESS THE INDUCED NEUROMODULATION Transcranial magnetic stimulation (TMS) is a non-invasive technique that induces a magnetic field on the skull which changes rapidly enough to induce electrical currents in underlying cortical tissue and to induce a neuromodulation effect (Hallet, 2000)
This study investigated the AS task as a psychophysical tool to assess the short-term neuromodulation that has been hypothesized to be induced by daily intermittent theta burst stimulation (iTBS) delivered over the left dorsolateral prefrontal cortex (DLPFC)
This indicates that the saccadic task might be a useful marker of the short-term neuromodulation, but a marker of mood changes too. This pilot study investigated the iTBS-induced short-term neuromodulation of the DLPFC. This is a crucial issue since little is known about the aftereffect of theta burst stimulation (TBS) over the DLPFC while being used in clinical research, in particular, with psychiatric disorders (Soekadar et al, 2009; Chistyakov et al, 2010; Holzer and Padberg, 2010; Plewnia et al, 2014)
Summary
RTMS TREATMENT OF DEPRESSION: NECESSITY TO ASSESS THE INDUCED NEUROMODULATION Transcranial magnetic stimulation (TMS) is a non-invasive technique that induces a magnetic field on the skull which changes rapidly enough to induce electrical currents in underlying cortical tissue and to induce a neuromodulation effect (Hallet, 2000). Repeated TMS (rTMS) has been used as a therapeutic tool for the treatment of drug-resistant mood disorders since the 1990s; patients receive a daily dose of rTMS over frontal regions for several weeks. The rationale for this treatment is that whereas a single rTMS session induces an early long-term potentiation of the targeted cortical area (short-term neuromodulation), cumulative rTMS sessions induce widespread late long-term potentiation across multiple neural circuits (Noda et al, 2013). Meta-analyses of rTMS as a treatment for depression have been recently published (Janicak et al, 2010; Slotema et al, 2010; George and Post, 2011; Berlim et al, 2014) All these studies agree that the therapeutic efficacy of rTMS is statistically significant but affects few patients. Berlim et al (2014) showed that about 30% of depressed patients receiving active excitatory rTMS responded to the treatment compared to 10% of patients who received sham treatment (analysis based on 29 studies using randomized, double-blind and sham-controlled trials)
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