Description
- Abstract:
- Heart Rate Variability (HRV) is examined in studies of exercise physiology and general medicine. It reflects the balance between the parasympathetic and sympathetic systems of the autonomic nervous system. HRV can be summarized using simple statistics (e.g. standard deviation), but has also been quantified by fractal scaling, a mathematical term that describes patterns observable across varying scales along which it is viewed. HRV typically decreases with increasing physical demands which is thought to reflect diminishing adaptability. Here, we test our hypothesis that fractal scaling and HRV correlate systematically with increasing cognitive demands. Detrended Fluctuation Analysis (DFA) is used to determine the dynamics of fractal scaling in heart rate with increasing cognitive load. DFA is a key statistical method used to analyze scaling behavior in time series. DFA can quantify scaling behavior in physiological systems (e.g. neuronal and cardiovascular), and demonstrate long-range temporal correlations therein. When the variability of inter-beat intervals scales increases linearly (in log-log space) with the number of beats over the window in which variability is measured, HRV exhibits fractal scaling. In contrast, when they become more random or more correlated, fractal scaling breaks down. Physiologically, this may be due to the withdrawal and reallocation of the vagal control (mediated by the vagus nerve) toward other immediate mental or physical demands. Vagal withdrawal may explain why decreasing HRV is associated with diminished adaptability. To explore the relationship between HRV and cognitive load, we utilize DFA to determine the fractal scaling dynamics in heart rate with increasing cognitive load. We test the prediction that fractal scaling in HRV both varies systematically with cognitive load and also correlates with individual differences in the fractal scaling of reaction times. We also test the prediction that fractal scaling in heart rate correlates with individual differences in subjective cognitive effort during task performance. Finally, because fractal scaling in neuronal oscillations has been shown to correlate with fractal scaling in behavior (both quantified by DFA), on-going work will test the hypothesis that diminished fractal scaling in HRV correlates with reduced fractal scaling in EEG signal and cognitive flexibility in demanding mental tasks.
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Citation
Tran, Lily,
"Fractal Scaling in Heart Rate Variability Dynamics in Relation to Cognitive Load"
(2022).
Summer Research Symposium.
Brown Digital Repository. Brown University Library.
https://doi.org/10.26300/c1fp-2019
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Summer Research Symposium
Each year, Brown University showcases the research of its undergraduates at the Summer Research Symposium. More than half of the student-researchers are UTRA recipients, while others receive funding from a variety of Brown-administered and national programs and fellowships and go …...