Dorsal Premotor Cortex Exerts State-Dependent Causal Influences on Activity in Contralateral Primary Motor and Dorsal Premotor Cortex

Abstract

During voluntary action, dorsal premotor cortex (PMd) may exert influences on motor regions in both hemispheres, but such interregional interactions are not well understood. We used transcranial magnetic stimulation (TMS) concurrently with event-related functional magnetic resonance imaging to study such interactions directly. We tested whether causal influences from left PMd upon contralateral (right) motor areas depend on the current state of the motor system, involving regions engaged in a current task. We applied short bursts (360 ms) of high- or low-intensity TMS to left PMd during single isometric left-hand grips or during rest. TMS to left PMd affected activity in contralateral right PMd and primary motor cortex (M1) in a state-dependent manner. During active left-hand grip, high (vs. low)-intensity TMS led to activity increases in contralateral right PMd and M1, whereas activity decreases there due to TMS were observed during no-grip rest. Analyses of condition-dependent functional coupling confirmed topographically specific stronger coupling between left PMd and right PMd (and right M1), when high-intensity TMS was applied to left PMd during left-hand grip. We conclude that left PMd can exert state-dependent interhemispheric influences on contralateral cortical motor areas relevant for a current motor task.

Coordination of Uncoupled Bimanual Movements by Strictly Timed Interhemispheric Connectivity

“…In previous studies, it has been demonstrated that while resting hands, interhemispheric PMd-M1 interactions are inhibitory (Mochizuki et al, 2004;Ni et al, 2009) but may turn into strictly timed and short-lasting facilitation during the premovement period (Koch et al, 2006;O'Shea et al, 2007;Liuzzi et al, 2010). By combining TMS and fMRI, Bestmann et al (2008) showed that a TMS pulse over the PMd elicits different effects on the motor regions of the opposite hemisphere depending on the state of the motor system. During hand grip, TMS led to activity increases in contralateral PMd and M1, whereas activity decreases were observed when the hands were at rest (Bestmann et al, 2008).…”

“…By combining TMS and fMRI, Bestmann et al (2008) showed that a TMS pulse over the PMd elicits different effects on the motor regions of the opposite hemisphere depending on the state of the motor system. During hand grip, TMS led to activity increases in contralateral PMd and M1, whereas activity decreases were observed when the hands were at rest (Bestmann et al, 2008). Thus, PMd appears to exert task-dependent influences over the opposite motor regions.…”

Vision Modulates Corticospinal Suppression in a Functionally Specific Manner during Movement of the Opposite Limb

“…In relation to motor output, it is thought that premotor cortex assumes a focusing role by modulating the activity of interneurons in M1 (Münchau et al, 2002). Recent studies using TMS (and combined fMRI) in humans suggest a functional influence of (left) PMd upon the opposite PMd (and M1) that is strongly state dependent: varying in accordance with the nature of the task being performed by the ipsilateral limb (Bestmann et al, 2008). During movement preparation, there is a corresponding influence of (right) PMd on opposite M1, which precedes interhemispheric interactions between the homologous primary motor areas (Liuzzi et al, 2010).…”

Conditional Selection of Contra- and Ipsilateral Forelimb Movements by the Dorsal Premotor Cortex in Monkeys

“…In humans, it has been reported that transcranial magnetic stimulation of the PMd changes excitability of the PMd and MI of the contralateral hemisphere (Bestmann et al 2008;Koch et al 2006Koch et al , 2007Mochizuki et al 2004), most likely via callosal connections (Di Lazzaro et al 1999;Ferbert et al 1992). Corresponding to these results, functional magnetic resonance imaging studies have demonstrated that the bilateral PMd was activated when conditional cues were applied to perform movements (Iacoboni et al 1998;Kurata et al 2000).…”