Non-Linear Analysis of Plethysmograms and the Effect of Communication on Dementia in Elderly Individuals

The authors of this chapter measured plethysmography and calculated the Largest Lyapunov Expornent (LLE) using non-linear analysis. They found that the value of LLE was significantly related to the severity of dementia and the communication skill in the ADL index for 144 elderly individuals. The authors developed a mathematical model to analyze the results by studying the information extracted from the plethysmogram data. Furthermore, data were collected when the central nerve was blocked by general anesthesia to evaluate the mathematical model. The pulse wave data indicated that the authors included information from the nucleus of the brain origin. In other words, they obtained conclusive evidence of dementia using the LLE and communication skills. The authors measured pulse waves while elderly individuals had a conversation. They calculated the activation of the sympathetic nerve and the parasympathetic (LF/HF, HF) response simultaneously. LLE that was activated by communication had a low HF, and the HF was high in individuals who were not activated. In other words, an effect of communication was observed in conscious elderly individuals. Communication scientifically indicated the mental activity of elderly individuals. DOI: 10.4018/978-1-60960-559-9.ch025