Figure 8.

Shift of the EEG power spectrum. In animals exposed to an ambient temperature (Ta) of 15°C, the EEG spectrum showed, during the cooling induced by muscimol injections (data from the M28 group (n = 7), A–D), a progressive reduction of the main spectral components and a progressive shift toward slow frequencies. The rewarming at Ta 28°C (M28 group (n = 7), E–H) induced an immediate large increase in the power of the main spectral component and a progressive shift of the spectrum toward fast frequencies. The rewarming at Ta 37°C for 1 h returning to 28°C afterward (M37 group (n = 6), I–L) induced a progressive shift of the spectrum toward fast frequencies. EEG power spectrum is expressed as the 1 h average spectrum (0.25 Hz resolution) calculated at the time shown by the vertical line in inserts. Inserts show the average time course of deep brain temperature (T_brain, filled circles) and Ta (continuous line) for a 12 h period (9:00–21:00) during the Injection Day. Vertical dotted lines highlight the temperature-dependent shift in the peak of the EEG Theta band during cooling at Ta 15°C and rewarming at Ta 28°C and Ta 37°C.