Heart Rate and Heart Rate Variability Assessment Identifies Individual Differences in Fear Response Magnitudes to Earthquake, Free Fall, and Air Puff in Mice
(A) For each type of fearful stimuli (air puff, free fall, and earthquake, respectively), the fear resistance index (FRI) was developed and calculated from comprehensive evaluation index by combining five individual HR parameters. Individual mice were ranked in the order of the fear resistance index (air puff, the left panel; free fall, the middle panel; earthquake, the right panel). The fear resistance index of each mouse revealed the high consistency of cardiac responses to the three types of fearful stimuli in individual mice. (B) The regression analysis of fear resistance index (FRI) in seven mice between air puff and free fall (the left panel), between free fall and earthquake (the middle panel), and between earthquake and air puff (the right panel) was carried out respectively. Significant correlations were observed across all the three different types of fearful stimuli.