Heart rate variability analysis under varied task difficulties in mental arithmetic performance

Mental calculation demanding tasks cause changes in the autonomic modulation of the cardiac function. Heart rate variability (HRV) is a parameter to understand the autonomic changes. To examine HRV in young individuals in the performance of two levels of arithmetic mental calculation tasks. We assessed 22 participants (18-25years; both male and female) who performed two levels of mental arithmetic calculations, i.e., 15 easy and 15 calculative. Each task was for 10s, for both easy and calculative and presented in random manner, through Superlab 4.5 (Cedrus Inc.) and electrocardiogram data were acquired by MP35 (Biopac Inc., Goleta, California, USA). Acqknowledge 4.1 and KUBIOS 2.1 software were used for HRV analysis. Decreased heart rate in calculative task as compared to easy task (p<0.01) was analyzed. SD1 and SD2 values were higher during calculative task. However, short-term fluctuation (1) was higher and the long-term fluctuation (2) was found to be lower for the easy task. Task comparative changes in the HRV parameters (Low frequency and High frequency) including Heart Rate, showed that transition from easy to calculative task and vice-versa showed an increase in all these parameters and a decrease in same parameters, respectively. As the task difficulty increases, heart rate decreases along with significant variations in different linear and non-linear HRV parameters; which are influenced by the autonomic nervous system under mental-arithmetic resulting in mental stress.