title: Long-latency modulation of motor cortex excitability by ipsilateral posterior inferior frontal gyrus and pre-supplementary motor area.
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 the first time, longer-latency causal interactions of the posterior inferior frontal gyrus (pIFG) and pre-supplementary motor area (pre-SMA) with M1 at rest. A suprathreshold test stimulus (TS) was applied over M1 producing a motor-evoked potential (MEP) in the relaxed hand. Either a subthreshold or a suprathreshold conditioning stimulus (CS) was administered over ipsilateral pIFG/pre-SMA sites before the TS at different CS-TS inter-stimulus intervals (ISIs: 40-150 ms). Independently of intensity, CS over pIFG and pre-SMA (but not over a control site) inhibited MEPs at an ISI of 40 ms. The CS over pIFG produced a second peak of inhibition at an ISI of 150 ms. Additionally, facilitatory modulations were found at an ISI of 60 ms, with supra- but not subthreshold CS intensities. These findings suggest differential modulatory roles of pIFG and pre-SMA in M1 excitability. In particular, the pIFG -but not the pre-SMA- exerts intensity-dependent modulatory influences over M1 within the explored time window of 40-150 ms, evidencing fine-tuned control of M1 output.
authors.affiliation: Dipartimento di Psicologia and Centro studi e ricerche in Neuroscienze Cognitive, Campus di Cesena, Università di Bologna 47521 Cesena, Italy.|IRCCS Fondazione Santa Lucia, 00179 Rome, Italy.|Dipartimento di Psicologia, Sapienza Università di Roma, 00185 Rome, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Fiori
authors.affiliation: Dipartimento di Psicologia and Centro studi e ricerche in Neuroscienze Cognitive, Campus di Cesena, Università di Bologna 47521 Cesena, Italy.
authors.forename: Emilio
authors.initials: E
authors.lastname: Chiappini
authors.affiliation: Dipartimento di Psicologia and Centro studi e ricerche in Neuroscienze Cognitive, Campus di Cesena, Università di Bologna 47521 Cesena, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Soriano
authors.affiliation: Dipartimento di Psicologia and Centro studi e ricerche in Neuroscienze Cognitive, Campus di Cesena, Università di Bologna 47521 Cesena, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Paracampo
authors.affiliation: Centre for Brain Science, Department of Psychology, University of Essex, UK.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Romei
authors.affiliation: Dipartimento di Psicologia and Centro studi e ricerche in Neuroscienze Cognitive, Campus di Cesena, Università di Bologna 47521 Cesena, Italy.|IRCCS Fondazione Santa Lucia, 00179 Rome, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Borgomaneri
authors.affiliation: Dipartimento di Psicologia and Centro studi e ricerche in Neuroscienze Cognitive, Campus di Cesena, Università di Bologna 47521 Cesena, Italy.|IRCCS Fondazione Santa Lucia, 00179 Rome, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Avenanti
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D012146:Rest / Q000502:physiology; D050781:Transcranial Magnetic Stimulation