The sensorimotor network (SMN), also known as the somatomotor network, is a large-scale brain network that integrates external sensory input with internal motor output to plan and coordinate voluntary movement [1] . At its core, the SMN includes cortical regions such as: the primary motor cortex (M1, precentral gyrus), the primary somatosensory cortex (S1, postcentral gyrus), the premotor cortex and the supplementary motor area (SMA). [2] [3] [4] Additionally, the auditory cortex [2] and the visual cortex [3] may be included in the SMN as well. The SMN is activated during motor tasks, such as finger tapping, indicating that the network readies the brain when performing and coordinating motor tasks. [1] [2] [3] [4]
As one of the brain's main neural networks, the SMN interacts with other cortical and subcortical regions in order to facilitate sensory processing and motor output everyday. More specifically, the SMN is involved in recurrent cortico-subcortical loops that involve the basal ganglia and cerebellum. Cortico-striato-thalamo-cortical (CSTC) circuits connect SMN cortical areas with subcortical regions such as the striatum, globus pallidus, and thalamus, allowing dopaminergic basal ganglia pathways (direct and indirect) to influence the selection and strength of our everyday motor output. [5] At the same time, cortico-cerebello-thalamo-cortical (CCTC) loops connect sensorimotor and premotor cortices to the cerebellar cortex and deep nuclei, which are thought to be involved in facilitating smooth, voluntary, precise, and coordinated fine motor output. [6]
At the cortical level, the SMN interacts with networks involved in attention, executive function, control, and valuation. Functional connectivity studies show associations between the SMN, dorsal attention and frontoparietal control networks during goal-directed actions, as well as interactions with limbic and salience networks when actions are driven by affective or reward cues. [5] As one ages, the SMN activity becomes less segregated from these other networks, and these lines and boundaries separating the SMN from its neighboring association systems begin to blur. As a result, connectivity within these networks decreases, which correlates to reduced motor output and overall performance. [7]
Abnormal patterns of connectivity between the SMN and these subcortical and associative networks are a recurring theme found across movement disorders. For example, imaging studies in patients with Parkinson's disease showed a decrease in functional connectivity within cortical SMN regions and a disruption in communication between SMN, basal ganglia, and cerebellar networks, all crucial for proper motor performance. Some modern treatment methods include dopaminergic medication or deep-brain stimulation to partially normalize some of these network changes and disruptions in motor performance. [8]
Dysfunction in the SMN has been implicated in various neuropsychiatric disorders.
In 2019, Uddin et al. proposed that pericentral network (PN) be used as a standard anatomical name for the network. [2]