###### Abstract
Serious games are games created for a purpose other than pure entertainment [9]. Serious games focused on health were used to help with health monitoring [10; 11; 12], detection and management of health conditions [13; 14; 15; 16], and therapy and rehabilitation [17; 18; 19]. Serious games designed for the elderly have been developed over the years with a variety of goals in mind, ranging from physical therapy, balance training, and mood or stress management [20; 21; 22]. While these games had a positive effect on the elderly, no physiological measures were considered. Since physiological measurements are difficult to influence consciously, they have been proved to be more objective [23]. By recording and analyzing these physiological signals, the games and possibly other applications designed for the elderly can be designed better towards their needs. The relationship of cognition and HRV features has been investigated in several studies, and the results indicate the influence of the ANS in cognition. HRV is generally defined as the variation on the time interval between a person's heartbeats. The R-to-R (RR) intervals are calculated by acquiring the time between each R wave in the QRS complex of the ECG signal. Normalized RR (NN) intervals are also calculated in a similar method, but artifacts and noise from the signal were removed. Most HRV features are then derived from RR or NN intervals [24]. There were some HRV features that have been shown to have a correlation to a person's cognitive abilities. High resting HRV values correlate to better performance in different cognitive domains. Some of the HRV features to note are high-frequency (HF) power, low-frequency (LF) power, standard deviation of NN intervals (SDNN) and root mean square of successive RR interval differences (RMSD) [25]. From these results, autonomic markers such as HRV features, can be used as biomarkers for cognitive impairment [25; 26]. However, not all studies observed a relationship. Some cognitive domains and tasks implemented in these studies found no correlation between the subjects' cognitive performance and their HRV. In this study, we wanted to investigate if there are significant difference in the ANS activity between cognitively normal and cognitively impaired elderly subjects as they play serious games through their measured HRV. These serious games were designed for the elderly, one game for testing the cognitive aptitude and two games testing their processing speed and reaction time [27; 28]. The purpose of investigating the HRV response is to know how these serious games affect elderly people of different cognitive status. In addition to this, we also compared the two groups for their cognitive function through their game performance. We also explored the use of HRV and game performance features measured from elderly subjects and its application for automated detection for cognitive impairment using machine learning (ML). The subject criteria, experimental design, physiological measurement, signal preprocessing, feature extraction, statistical analysis, feature selection and classification are shown in detail in Section 2. The results from the experiment and data analysis are presented in Section 3. The discussion and interpretation of these results are in Section 4. Finally, conclusions and future work are presented in Section 5.