Dynamics of sleep oscillations is coupled to brain temperature on multiple scales.

Every form of neural activity depends on temperature, yet its relationship to brain rhythms is poorly understood. In this work, we examined how sleep spindles are influenced by changing brain temperatures, and how brain temperature is influenced by sleep oscillations. We employed a novel thermoelectrode designed for measuring temperature while recording neural activity. We found that spindle frequency is positively, duration is negatively correlated with brain temperature. Local heating of the thalamus replicated the temperature dependence of spindle parameters in the heated area only, suggesting biophysical, rather than global modulatory mechanisms, a finding also supported by a thalamic network model. Finally, we show that switches between oscillatory states also influence brain temperature on a shorter and smaller scale. Epochs of paradoxical sleep, as well as the infra-slow oscillation were associated with brain temperature fluctuations below 0.2°C. Our results highlight that brain temperature is massively intertwined with sleep oscillations on various timescales. This article is protected by copyright. All rights reserved.