Understanding the role of the primary somatosensory cortex: Opportunities for rehabilitation

Abstract

Emerging evidence indicates impairments in somatosensory function may be a major contributor to motor dysfunction associated with neurologic injury or disorders. However, the neuroanatomical substrates underlying the connection between aberrant sensory input and ineffective motor output are still under investigation. The primary somatosensory cortex (S1) plays a critical role in processing afferent somatosensory input and contributes to the integration of sensory and motor signals necessary for skilled movement. Neuroimaging and neurostimulation approaches provide unique opportunities to non-invasively study S1 structure and function including connectivity with other cortical regions. These research techniques have begun to illuminate casual contributions of abnormal S1 activity and connectivity to motor dysfunction and poorer recovery of motor function in neurologic patient populations. This review synthesizes recent evidence illustrating the role of S1 in motor control, motor learning and functional recovery with an emphasis on how information from these investigations may be exploited to inform stroke rehabilitation to reduce motor dysfunction and improve therapeutic outcomes.

On the dependence of response inhibition processes on sensory modality

“…The lower activation of brain regions known to constitute a response inhibition network together with better behavioral response inhibition performance suggests that response inhibition networks become more efficient when being triggered by the tactile modality. Interestingly the identified brain regions showing weaker activation in the tactile than in the visual condition, especially the SFG (BA6), have been shown to yield strong structural neuroanatomical connections to somatosensory association cortices [Borich et al, ; Fang et al, ]. It may be speculated that this structural neuroanatomical property is important for the effects observed in the SFG and MFG in the tactile experimental condition.…”

“…Interestingly, the SMA and the superior frontal cortex show strong axonal connections to somatosensory associations cortices [Borich et al, ; Fang et al, ], which has also been shown in neuroanatomical studies in macaques [Luppino et al, ]. Furthermore, parietal somatosensory regions show strong connections to posterior parietal areas [Borich et al, ] which are important for sensory motor integration [Andersen and Buneo, ] and have recently been shown to be involved during response inhibition [Dippel et al, ]. Finally, changes in somatosensory functions have a direct effect on motor cortical areas and the control of responses [Borich et al, ].…”

“…However, unlike conventional views of primary sensory areas several lines of evidence suggest that the (primary) somatosensory cortex is able to perform multisensory integration processes [Borich et al, ; Driver and Noesselt, ] and is involved in merging multimodal information, e.g. from the visual modality [Borich et al, ]. This is of importance, because recent results suggest that multisensory information has a strong impact on efficient response inhibition processes [Chmielewski et al, ].…”

Motor compensation and its effects on neural reorganization after stroke

“…Spasticity due to hyperexcitability of the stretch reflex can develop after stroke 35 , and its severity is correlated with the severity of motor impairments 36 . Motor impairments co-occur to varying degrees with impaired somatosensation 37,38 , which is associated with damage to ascending somatosensory pathways 39 .…”

Measuring motor-training induced neuroplasticity using diffusion and functional MRI: a sensitive, pathology-robust approach

“…Motor output from the brain predominantly originates from the sensorimotor cortex, 258,259 and it was from the corticospinal tract that we saw an increase in FA, driven predominantly by changes in radial diffusivity. From the same dataset we previously reported changes in cortical thickness, fMRI maps, and TMS maps (Chapter 5).…”