Heart RateVariabiiity Reference toAmbient during Mental Task with Temperature

The purpose of this study was to eva]uate the cardiae autonomie contro] over mental task uiider various ambjent temperatures (210C, 280C and 35VC), Seven healthy male subjeets engaged in the mental tasks, which consisted of distinetive reaetion-time tasks. Respiratory ceefficient of variation of instantaneous heart rate (CVREsp) , derived from the eross-eorrelation funetion between heart rate and respiratory curve, was used as a par'ameter to assess parasyrnpathetic nervous funations. The difference between total coefficient of variation (CViHR) and CVREsp "ias used as a parameter to assess sympathetic nervous functions, The mean heart rate inereased at high ambient temperature (350C) and also during mental task. Both the effects of ambient temperature and task eonditions were significant on heart rate, and aiso on CVJHR, Moreover, the effects of ambient temperature and task eenditions in CVmR were divided into the effect of ambient temperature on CVREsp and the effect of task conditions on the difference between Cit'THn and CVREs?. These results implied that respiratory modulated parasympathetlc activity might control basal t,he effeet of ambient temperature, and the other components including sympathetic activity eentribute to the increase in heart rate due to mental task. (Ajopn Uuman Sc7. i8 C6), 2i9-223, 1999)