Sleep spindles, transient bursts of rhythmic activity during non-rapid eye movement (NREM) sleep, are generated by the thalamocortical network through an intricate interplay between the thalamus and the cortex. Emerging research has shed light on the role of sleep spindles in cognitive function, memory consolidation, and overall brain health. Using a behavioral genetics approach in female and male adolescent humans, this study examined the degree to which sleep spindles (measured via high-density sleep EEG) and thalamic volume (measured via MRI) are driven by common genetic and environmental factors. Here we show a strong correlation between thalamic volume and sleep spindle amplitude and density. Bayesian structural equation modelling estimated that over posterior regions genetic factors accounted for approximately half of the covariance between sleep spindle activity and thalamic volume. Our findings demonstrate that genetic factors play a role in shaping the structural and functional integrity of the thalamocortical network, with implications for understanding how these processes contribute to neurodevelopmental outcomes.Significance statement Sleep spindles, oscillatory activity generated in the thalamus, are crucial for cognitive functions and brain health. This study investigated the joint genetic and environmental influences on sleep spindles and thalamic volume in adolescents. Our findings suggest a significant overlap in genetic factors influencing thalamic volume and spindle amplitude over posterior brain regions. Given that sleep spindle activity is altered in several brain disorders involving the thalamocortical system, this work not only enhances our understanding of the biological phenomena underlying the neuroanatomical substrates of the sleep EEG but also offers crucial insights for developing targeted interventions in neurodevelopmental disorders.
