Brain temperature affects quantitative features of hippocampal sharp wave ripples

Biochemical mechanisms are temperature-dependent. Brain temperature shows wide variations across brain states, and such changes may explain quantitative changes in network oscillations. Here we report on the coupling of various hippocampal sharp wave ripple features to brain temperature. Ripple frequency, occurrence rate and duration correlated with temperature dynamics. By focal manipulation of the brain temperature in the hippocampal CA1 region, we show that ripple frequency can be increased and decreased by local heating and cooling, respectively. Changes of other parameters, such as the rate of SPW-R and ripple duration were not consistently affected. Our findings suggest that brain temperature in the CA1 region plays a leading role in affecting the ripple frequency, whereas other parameters of SPW-Rs may be determined by mechanisms upstream from the CA1 region. These findings illustrate that physiological variations of brain temperature exert important effects on hippocampal circuit operations.