Open AccessThe human dorsal premotor cortex facilitates the excitability of ipsilateral primary motor cortex via a short latency cortico‐cortical route
Author(s) -
Groppa Sergiu,
Schlaak Boris H.,
Münchau Alexander,
WernerPetroll Nicole,
Dünnweber Janin,
Bäumer Tobias,
van Nuenen Bart F.L.,
Siebner Hartwig R.
Publication year - 2012
Publication title -
human brain mapping
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.005
H-Index - 191
eISSN - 1097-0193
pISSN - 1065-9471
DOI - 10.1002/hbm.21221
Subject(s) - transcranial magnetic stimulation , neuroscience , premotor cortex , motor cortex , primary motor cortex , facilitation , stimulation , stimulus (psychology) , ctbs , evoked potential , psychology , dorsum , latency (audio) , anatomy , medicine , computer science , psychotherapist , telecommunications
Abstract In non‐human primates, invasive tracing and electrostimulation studies have identified strong ipsilateral cortico‐cortical connections between dorsal premotor‐ (PMd) and the primary motor cortex (M1 HAND ). Here, we applied dual‐site transcranial magnetic stimulation (dsTMS) to left PMd and M1 HAND through specifically designed minicoils to selectively probe ipsilateral PMd‐to‐M1 HAND connectivity in humans. A suprathreshold test stimulus (TS) was applied to M1 HAND producing a motor evoked potential (MEP) of about 0.5 mV in the relaxed right first dorsal interosseus muscle (FDI). A subthreshold conditioning stimulus (CS) was given to PMd 2.0–5.2 ms after the TS at intensities of 50‐, 70‐, or 90% of TS. The CS to PMd facilitated the MEP evoked by TS over M1 HAND at interstimulus intervals (ISI) of 2.4 or 2.8 ms. There was a second facilitatory peak at ISI of 4.4 ms. PMd‐to‐M1 HAND facilitation did not change as a function of CS intensity. Even at higher intensities, the CS alone failed to elicit a MEP or a cortical silent period in the pre‐activated FDI, excluding a direct spread of excitation from PMd to M1 HAND . No MEP facilitation was present while CS was applied rostrally over lateral prefrontal cortex. Together our results indicate that our dsTMS paradigm probes a short‐latency facilitatory PMd‐to‐M1 HAND pathway. The temporal pattern of MEP facilitation suggests a PMd‐to‐M1 HAND route that targets intracortical M1 HAND circuits involved in the generation of indirect corticospinal volleys. This paradigm opens up new possibilities to study context‐dependent intrahemispheric PMd‐to‐M1 HAND interactions in the intact human brain. Hum Brain Mapp, 2012. © 2010 Wiley‐Liss, Inc.