# Adults with Down syndrome display altered entrainment of occipital cortical neurons

## TL;DR

Adults with Down syndrome show weaker brain wave responses and higher background brain activity in the visual cortex compared to typical adults.

## Contribution

This study reveals novel neural entrainment and spontaneous activity differences in the occipital cortex of adults with Down syndrome.

## Key findings

- Adults with Down syndrome exhibit weaker entrainment of occipital cortical neurons to a 15 Hz visual stimulus.
- They show elevated spontaneous activity during the prestimulation baseline period compared to controls.
- Altered resting cortical rhythms may affect perceptual and cognitive processing in Down syndrome.

## Abstract

Down syndrome is commonly associated with a trisomy of chromosome 21 that often presents an accelerated aging profile and higher probability of developing Alzheimer’s disease-like symptoms at a relatively early age. However, the physiological changes that may contribute to such symptoms remain poorly understood. To begin to address this knowledge gap, we used magnetoencephalographic neurophysiological imaging to assess the entrainment of occipital cortical neurons to a 15 Hz visual stimulus in a cohort of adults with DS without a dementia diagnosis (N = 26; Age = 27.65 ± 9.55 years) and a demographically matched cohort of neurotypical controls (N = 22; Age = 30.81 ± 8.02 years). Our results indicated that adults with Down syndrome exhibit substantially weaker entrainment of the occipital cortical neurons and elevated spontaneous activity during the prestimulation baseline period compared with the controls. These results suggest that there are alterations in the integrity of occipital neural populations that may be attributable to an imbalance in local GABAergic activity and/or disruption in cholinergic pathways. These changes may affect the strength of resting cortical rhythms, leading to the elevated spontaneous activity observed here, which has been linked to reductions in the dynamic range of neural populations and impairments in perceptual and cognitive processing. These novel results advance our understanding of the occipital cortical physiology seen in adults with Down syndrome and provide foundational knowledge for the development of biomarkers for the early detection of accelerated aging and cognitive decline in those with Down syndrome.

Chinen et al. report that adults with Down syndrome have weaker entrainment of the occipital cortical neurons and have an elevated spontaneous activity relative to controls. The altered strength of the resting cortical rhythms likely impacts the available dynamic range of the neural populations.

Graphical Abstract