Study On Association Between Ambient Temperature And Brain Gray Matter Volume Emotion In Normal Young Adults

Objective:Environmental factors,such as temperature,can shape character by influencing human daily activities and habitual behavior.Previous studies have shown that environmental factors(such as socio-economic,family and nature environment)can affect the gray matter volume of the human brain,but the relationship between the ambient temperature and the gray matter volume of the human brain is still unclear.The purpose of this study was to investigate whether the ambient temperature affected the gray matter volume of the normal young people,and then to explore whether the gray matter volume of the brain area affected by the ambient temperature was related to emotion(anxiety and depression).Methods:In this study,brain structural magnetic resonance imaging was performed in 628 normal Chinese young adults using voxel-based morphological measurement to calculate the gray matter volume(GMV)of whole brain voxels.Beck depression inventory(BDI),state-trait anxiety questionnaire(STAI)was used to measure the emotional state of the subjects,and STAI was divided into two scales: state anxiety scale(SAI),which described a transient unpleasant emotional experience;trait anxiety scale(TAI)describes a relatively stable,individual anxiety tendency as a personality trait.The environmental factors questionnaire was used to collect the living areas and years of life of the subjects since they were born,and the sites were transformed into coordinates,and the google earth engine(GEE)was used.The annual mean land surface temperature(LST)within the radius of 1km,including the annual mean daytime land surface temperature(LST-D),and the annual mean nighttime surface temperature(LST-N),the mean annual mean LST of all the years provided by the subjects was calculated as the average LST.The difference between average LST-D and LST-N is calculated as the average diurnal temperature difference(DTV).Using spm8 software,a voxel-based general linear model analysis method was used to control age,sex and educational years to explore the brain regions associated with GMV and mean LST,DTV,FWE(P<0.05)method was used for multiple comparison and correction.The gray matter volume of the brain area with the above correlation was extracted and the correlation between GMV and LST and anxiety and depression scores were analyzed.According to China's north-south latitude value(34 °N)all the subjects were divided into two groups,to explore the GMV between group differences of brain regions,and further analysis of these brain regions GMV value and the correlation among LST and sentiment index.The mediating effect analysis was used to explore whether the ambient temperature affects the human brain gray matter volume and then the emotional state.Results:(1)Emotional and ambient temperature index.The score of BDI was 0-23(mean 2.32±3.45),SAI score was 20-57(mean 28.89 ± 6.35),TAI score was 20-65(mean 32.57 ± 6.49).The mean LST-D 13.79-32.37?(mean 25.15±2.35),LST-N-5.71-19.56?(mean 7.88±3.13)and DTV 9.80-26.24?(mean 17.27±2.85).(2)Correlativity between whole brain GMV and LST based on voxel.There was a negative correlation between the right precuneus GMV and LST-D(MNI:12,-66,47;cluster:48;P<0.001),the left middle frontal gyrus GMV was positively correlated with LST-N(MNI:-39,29,29;cluster:37;P < 0.001),The left temporal pole GMV was negatively correlated with LST-N(MNI:-47,23,-26;cluster:87;P < 0.001),and the left cuneus GMV was positively correlated with DTV(MNI:-18,-104,-5;cluster:52;P<0.001).(3)Correlation between the emotional scores and LST & GMV.LST-N was negatively correlated with SAI(r =-0.083,P = 0.038)and TAI score(r =-0.095,P = 0.017).There was no significant correlation between LST and BDI scores.The GMV value of the left temporal pole was negatively correlated with the TAI score(r =-0.081,P = 0.042).GMV values of right precuneus,left medial frontal gyrus and cuneus were not significantly correlated with BDI and STAI scores.(4)Intermediate effect test.The mediating effects of the four brain regions related to ambient temperature(right precuneus,left medial frontal gyrus,left cuneus and left temporal pole)on LST,SAI and TAI were not significant.(5)Differences in GMV between northern and southern subjects and the correlation with LST.The brain regions of the northern subjects were larger than those of the southern subjects,including the left temporal pole and the left superior temporal gyrus,and the left superior temporal gyrus were related to LST-N(r =-0.137,P = 0.001).The left middle frontal gyrus of the northern subjects was smaller than that of the southern ones,and the GMV was positively correlated with LST-N(r = 0.095,P = 0.018).Conclusion:In this study,it was found that ambient temperature was correlated with GMV(right precuneus,left medial frontal gyrus,left temporal pole,and left cuneus)in normal young people,and GMV in the left temporal pole was correlated with anxiety.Ambient temperature is negatively correlated with anxiety.The research structure indicates that ambient temperature affects brain gray matter structure and anxiety state,suggesting that environmental factors should be considered in the study of brain structure of emotional disorders,such as mental diseases.