Adults with down syndrome exhibit altered somatosensory cortical inhibition.

Down syndrome (DS) is a developmental genetic disorder that is associated with an accelerated aging profile and high probability of early incidence Alzheimer's disease like symptoms. It is well established that there are morphological differences in the brains of adults with DS, but the net impact of the genetic disruption on cortical function remains poorly understood. To address this knowledge gap, we used magnetoencephalographic (MEG) brain imaging to assess the somatosensory cortical activity elicited by a paired-pulse electrical stimulation of the right median nerve of adults with DS (N = 19; Age = 28.05 ± 7.9 yrs.) and neurotypical controls (NT) (N = 21; Age = 30.81 ± 8.2 yrs.). sLORETA was used to image neural responses to the somatosensory stimulation, which were centered on the left central sulcus posterior to the motor hand knob region. Our results revealed that adults with DS had weaker somatosensory cortical activity after the second electrical stimulation in the paired-pulse paradigm (DS = 594.1 ± 194.22 AU; NT = 750.48 ± 256.6; P = 0.038) and a pronounced hyper-gating response (DS = 78.9 ± 6.8 %; NT = 87.4 ± 9.9 %; P = 0.003). Together, these results suggest that adults with DS may have an imbalance in the excitatory/inhibitory ratio. These novel data enhance our understanding of the neurophysiological aberrations associated with DS and may hold promise in understanding the origins of Alzheimer's disease like symptoms in this population. Future studies should examine whether these inhibitory alterations are restricted to the sensorimotor cortices or extend across the brain.