Neurocognitive architecture in humans is sexually dimorphic as observed by hemispheric lateralization of sleep spindles

• Males and females are different in the sense that they each have distinct spindle oscillations. They differ in the hemispheric lateralization of their neurocognitive processes as well.
• The hemispheric lateralization of both male and female cognitive functions was also shown to vary based on an age-dependent manner.
• Previous studies had little data on the hemispheric lateralization of spindle oscillations, and there were no reported differences in the hemispheric lateralization of sleep spindles based on either sex or age. The researchers set out to fill this gap by the description of the hemispheric lateralization of sleep spindles in healthy human subjects.
• The researchers conducted a retrospective multi-center study that took and unified data from three distinct groups: N = 251, age range: 4?69 years, 122 females. They also analyzed the amplitude, density, and duration of slow (frontally dominant) and fast (centroparietally dominant) spindles by using the individual adjustment method. Then hemispheric lateralization was quantified with the (L ? R)/mean (L, R) index.
• Orbitofronto-temporo-occipital and parietal fast sleep spindle measures are left lateralized, while prefrontal spindle amplitude is characterized by right hemispheric dominance. With each increase in the age of a male, there is an increase in the fast spindle density’s left lateralization as well as the duration in the temporal and orbitofrontal regions. The same could not be said for females.
• Females are different in that they are characterized by higher left hemispheric dominance in occipitally measured fast spindle durations as opposed to males.

The researchers concluded that there is asymmetrical distribution of sleep spindles over the brain’s two hemispheres. Moreover, the phenomenon is sexually dimorphic and region-specific, which signifies sex differences in neurocognitive architectures.