Differences in Activity of the Brain Networks During Voluntary Motor Tasks Engaging the Local and Global Muscular Systems of the Lower Trunk.

Low back pain constitutes a multidimensional problem of largely unknown origin. One of the recent theories explaining its frequent occurrence includes speculative statements on patterns of central nervous system activity associated with the control of so-called local and global muscles of the lower trunk. The objective of the study was to verify whether there is a difference in the activity of the brain during selective, voluntary contraction of the local and global abdominal muscles as assessed by functional MRI. Twenty healthy subjects participated. An experimental design was applied with repeated measurements of the blood-oxygen-level-dependent signal from the brain during voluntary contraction of the local and global abdominal muscles, performed in random order. Prior to registration, a 2-week training period was introduced, aiming to master the experimental motor tasks. The magnetic resonance imaging (MRI) data were processed using the FMRIB Software Library (Oxford, UK). Brain areas showing significant activations/deactivations were identified and averaged across all participants, and intercondition differential maps were computed. Areas of significant intercondition differences were linked to the corresponding anatomical structures and ascribed to the default mode functional brain network and to the sensorimotor network. Contraction of the local abdominal muscles elicited more pronounced activity of the brain cortex, basal ganglia, and cerebellum. This suggests that motor control of the abdominal musculature consists of two modes of brain activity and that control of the local muscles may be a more challenging task for the brain. Moreover, contraction of the local muscles elicited more distinct deactivation of the default mode network, which may have implications for diagnostics and therapy of low back pain.