1997 – A short-term poikilothermic period occurs just after paradoxical sleep onset in humans: characterization changes in sweating effector activity

We examined the changes in sudorific effector activity in five healthy young (21‐23 y) subjects just before, during and just after successive paradoxical sleep (PS) phases. Local sweat rates were evaluated minute by minute over the chest (ṁ_cs). Previous observations, showing that ṁ_cs levels dropped before paradoxical sleep onset was electrophysiologically scored, were confirmed. At the end of this period of ṁ_csdepression, which in the present study coincided with paradoxical sleep onset, we show for the first time a short period (3–7 min) (period I) during which sweat production completely disappeared. A second period then followed (period II), at the very beginning of which ṁ_cs was re‐elicited and thereafter increased in close correlation with paradoxical sleep duration. During period 11, the remaining inhibiting influences (maximal during period I) and their releases could be specified by the successive valleys (indicating ṁ_csinhibition) and peaks (indicating release of the ṁ_cs inhibition) drawn by the minute by minute m_cs changes. These inhibitions became weaker as paradoxical sleep advanced. Given the strategic position of period I (at paradoxical sleep onset) and the total m_csabolition therein observed, it may be assumed that this poikilothermic state is the re‐emergence of the ‘ancestral’ mode of body temperature regulation. From a thermophysiological point of view, period II may be considered as more ‘modern’ and directly related to the extension of paradoxical sleep in humans. This extension could be underlain by the unique development of our cognitive and/or learning functions.