Abstract
There is evidence to suggest that motor execution and motor imagery both involve planning and execution of the same motor plan, however, in the latter the output is inhibited. Currently, little is known about the underlying neural mechanisms of motor output inhibition during motor imagery. Uncovering the distinctive characteristics of motor imagery may help us better understand how we abstract complex thoughts and acquire new motor skills. The current study aimed to dissociate the cognitive processes involved in two distinct inhibitory mechanisms of motor inhibition and motor imagery restraint. Eleven healthy participants engaged in an imagined GO/NO-GO task during a 7 Tesla fMRI experiment. Participants planned a specific type of motor imagery, then, imagined the movements during the GO condition and restrained from making a response during the NO-GO condition. The results revealed that specific sub-regions of the supplementary motor cortex (SMC) and the primary motor cortex (M1) were recruited during the imagination of specific movements and information flowed from the SMC to the M1. Such condition-specific recruitment was not observed when motor imagery was restrained. Instead, general recruitment of the posterior parietal cortex (PPC) was observed, while the BOLD activity in the SMC and the M1 decreased below the baseline at the same time. Information flowed from the PPC to the SMC, and recurrently between the M1 and the SMC, and the M1 and the PPC. These results suggest that motor imagery involves task-specific motor output inhibition partly imposed by the SMC to the M1, while the PPC globally inhibits motor plans before they are passed on for execution during the restraint of responses.
Highlights
The neural correlates of voluntary movement and the imagination of the same movements overlap extensively (Jeannerod, 1995; Decety, 1996a; Hotz-Boendermaker et al, 2008)
To establish the network involved in motor planning, motor imagery, and motor imagery restraint, we first identified the regions that showed significant BOLD activation during prompt, GO and NO-GO conditions, respectively (Supplementary Table S1)
Significant BOLD activation was observed during motor planning at the individual-level in the posterior parietal cortex (PPC) (Z > 2.3, p < 0.05, cluster-wise corrected; participant and condition mean VV ± SE; 5,838 ± 697 mm3) and the supplementary motor cortex (SMC) (1,402 ± 215 mm3) for all participants
Summary
The neural correlates of voluntary movement (i.e., motor execution) and the imagination of the same movements (i.e., motor imagery) overlap extensively (Jeannerod, 1995; Decety, 1996a; Hotz-Boendermaker et al, 2008). Studies suggest that motor execution and motor imagery involve planning of the same motor program; in the latter, the output is inhibited (Jeannerod, 1995; Decety, 1996b; Munzert et al, 2009). The inhibitory mechanisms underlying the motor imagery (i.e., GO) and NO-GO condition are cognitively different During the former, the actor does not know to inhibit the motor output until the NO-GO cue is given. The latter task can be achieved by general response restraint (i.e., motor restraint), while the actor does not have to perform other actions or cognitions simultaneously, unlike in the case of motor imagery (i.e., inhibiting and imagining the movement at the same time)
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