Long-latency modulation of motor cortex excitability by ipsilateral posterior inferior frontal gyrus and pre-supplementary motor area

• DOI: 10.1038/srep38396
• Publication Date: 2016-12-08T10:24:08Z
• Authors: Francesca Fiori; Emilio Chiappini; Marco Soriano; Riccardo Paracampo; Vincenzo Romei; Sara Borgomaneri; Alessio Avenanti
• Keywords: Supplementary motor area; Superior frontal gyrus; Stimulus (psychology); Premotor cortex

Abstract The primary motor cortex (M1) is strongly influenced by several frontal regions. Dual-site transcranial magnetic stimulation (dsTMS) has highlighted the timing of early (<40 ms) prefrontal/premotor influences over M1. Here we used dsTMS to investigate, for first time, longer-latency causal interactions posterior inferior gyrus (pIFG) and pre-supplementary area (pre-SMA) with M1 at rest. A suprathreshold test stimulus (TS) was applied producing a motor-evoked potential (MEP) in relaxed hand. Either subthreshold or conditioning (CS) administered ipsilateral pIFG/pre-SMA sites before TS different CS-TS inter-stimulus intervals (ISIs: 40–150 ms). Independently intensity, CS pIFG pre-SMA (but not control site) inhibited MEPs an ISI 40 ms. produced second peak inhibition 150 Additionally, facilitatory modulations were found 60 ms, supra- but intensities. These findings suggest differential modulatory roles excitability. In particular, –but pre-SMA– exerts intensity-dependent within explored time window 40-150 evidencing fine-tuned output.