Early determination of somatosensory cortex

Objectives: The developing brain possesses a high potential for post-lesional neuroplasticity after early brain lesions. Yet, this remarkable potential varies among the different functional systems – previous studies indicated that cortical plasticity of the somatosensory cortex is reduced compared to the language and motor system. Hence, we hypothesized that distinct brain structures involved in somatosensory processing are already prenatally determined. A congenital lesion affecting such early determined structures should then result in a somatosensory deficit later during life.

Methods: For this study, eleven patients with pre- or perinatally acquired unilateral cortico-subcortical stroke were subdivided into two groups depending on their somatosensory deficit (absent/mild vs. severe). MRI lesion-symptom mapping was applied to identify cortical structures commonly damaged in patients with a somatosensory deficit but typically spared in patients without a somatosensory deficit.

Results: Two distinct brain areas in the postcentral and supramarginal gyrus as well as the parietal operculum were identified. Using the stereotaxic probabilistic cytoarchitectonic atlas developed by the Jülich group, these regions could be assigned in part to the primary somatosensory cortex (S1), the parietal operculum (S2) and the supramarginal gyrus.

Conclusions: Our results argue for an early functional determination of these regions involved in somatosensory processing, going in line with previous studies demonstrating a limited potential for (re-)organisation within the somatosensory system.