Although we have several therapeutic interventions for depression, we lack an understanding of the mechanisms that underlie these interventions. To gain a better understanding of the mental health conditions we treat, diagnoses we make, and interventions we use, mechanistic understandings are necessary. There is evidence that exposure to depressive emotion and cognitions can yield therapeutic outcome. The current study examines the physiology associated with an intervention, expressive writing (EW), which other research has shown to produce therapeutic outcomes because it increases exposure to negative feelings. The current study tests the hypothesis that EW increases depressive emotion, cognition, and physiology. Depression has been associated with decreased respiratory sinus arrhythmia (RSA) and increased heart rate (HR). RSA and HR were measured while participants did either EW or a control writing (CW) task. Because measures of RSA can be confounded by respiratory rate (RR), RR was also measured and statistically controlled for. Results revealed that EW does not alter RSA or HR. Interestingly, exploratory regression analyses between HR and RR during EW suggest that EW might trigger exposure to a depressive physiological state. Further investigation into the relationship between HR and RR during EW is warranted. / Thesis / Master of Science (MSc) / The current study examines the emotion, cognition, and physiology associated with an intervention, expressive writing (EW), which is commonly used as a treatment for anxiety and depression. Research has suggested that EW produces therapeutic outcome because it increases exposure to negative feelings. The current study tests the hypothesis that EW increases depressive emotion, cognition, and physiology. Results suggest that EW increases depressive emotion and cognition but does not alter some of the physiological parameters that have been associated with depression in prior research. An unpredicted exploratory result was that EW affected the relationship between heart rate and respiratory rate. Further investigation into the relationship between heart rate and respiratory rate during EW is warranted.

A low cost Heart Beat Monitoring device (HBMD) for detecting heart beat in beats per minute is presented in this thesis. An optical technique called “Photoplethysmography” is utilized by attaching to the base of the finger for monitoring beat to beat pulsation. Two major design issues addressed in this research is to achieve a strong and accurate PPG signal and simultaneously minimizing physiological artefacts and interference. In order to achieve the aim and objectives of the research, this thesis thoroughly explores two new signal conditioning hardware designs. Firstly is the design and fabrication of a low cost reflectance mode PPG heart monitor using parallel port interfacing and secondly are the design and development of a portable transmission mode PPG heart monitor using microcontroller PIC16F84A and PIC16F87. Both PPG heart monitor design is divided into three phases. First is the detection of weak pulses through the fingertip. The PPG signal is then amplified, filtered and digitized by the signal processing unit. Finally the heart rate is calculated, analyzed and displayed on the computer using parallel port interface and on the liquid crystal display using microcontroller PIC16F87. A comprehensive circuit design and analysis work was implemented verified by Proteus VSM circuit simulations and laboratory experiments. Data is presented from the method comparison study in which heart rates measured with the reflectance mode PPG and portable transmission mode PPG heart monitor were compared with those measured with standard techniques on 13 human subjects. Benchmarking tests with approved pulse oximeter and blood pressure monitor Omron M6 reveals that the PPG heart monitor is comparable to those devices in displaying the heart rate. It is also verified through experiments that both PPG heart monitor design fulfill the objectives, including achieving strong and accurate PPG signal, reduction in physiological artefacts and interference and financially low in cost. As the conclusion, the current version of the reflectance mode PPG and portable transmission mode PPG heart monitor successfully measure heart rates fast and reliably in most subjects in different body position. The PPG heart monitor proposed avoid the need to apply electrodes or other sensors in the correct position which directly minimizes the preparation time drastically. This makes the PPG heart monitor more attractive for heart monitoring purpose and its advantage should be explored further. / Ministry of Higher Education Malaysia (MOHE) and Universiti Tun Hussein Onn Malaysia (UTHM)

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