Primary Motor and Sensory Cortex Activation during Motor Performance and Motor Imagery: A Functional Magnetic Resonance Imaging Study

TLDR

The study examined the intensity and spatial distribution of functional activation in the left precentral and postcentral gyri during actual motor performance and motor imagery of self‑paced finger‑to‑thumb opposition movements in fourteen right‑handed volunteers using fMRI. The authors located activated foci by plotting the time course of pixel signal intensities in the precentral or postcentral gyrus against single‑step or double‑step waveforms corresponding to different tasks. Significant increases in fMRI signal intensities were observed in the primary motor cortex and perirolandic areas during both motor performance and motor imagery, with motor performance showing larger increases (up to 2.1%) and motor imagery exhibiting about 30% of motor performance’s activation, supporting overlapping neural networks for the two conditions.

Abstract

The intensity and spatial distribution of functional activation in the left precentral and postcentral gyri during actual motor performance (MP) and mental representation [motor imagery (MI)] of self-paced finger-to-thumb opposition movements of the dominant hand were investigated in fourteen right-handed volunteers by functional magnetic resonance imaging (fMRI) techniques. Significant increases in mean normalized fMRI signal intensities over values obtained during the control (visual imagery) tasks were found in a region including the anterior bank and crown of the central sulcus, the presumed site of the primary motor cortex, during both MP (mean percentage increase, 2.1%) and MI (0.8%). In the anterior portion of the precentral gyrus and the postcentral gyrus, mean functional activity levels were also increased during both conditions (MP, 1.7 and 1.2%; MI, 0.6 and 0.4%, respectively). To locate activated foci during MI, MP, or both conditions, the time course of the signal intensities of pixels lying in the precentral or postcentral gyrus was plotted against single-step or double-step waveforms, where the steps of the waveform corresponded to different tasks. Pixels significantly (r > 0.7) activated during both MP and MI were identified in each region in the majority of subjects; percentage increases in signal intensity during MI were on average 30% as great as increases during MP. The pixels activated during both MP and MI appear to represent a large fraction of the whole population activated during MP. These results support the hypothesis that MI and MP involve overlapping neural networks in perirolandic cortical areas.