Punto de Acceso Cisco (Cisco Aironet Series AP).

The sense of anxiety is often connected to a disturbance of one or more of the somatic functions, for example respiration, heart inaction, vasomotor innerva- tions of the skin of the hand, or glandular activity (Tyrer, 1999). While there are a large number of physiological measures, human electrical activity is one of the most widely used in psycho-physiological measures, including Electrocar- diogram (ECG), Electromyogram (EMG), and Galvanic Skin Response (GSR) (Andreassi, 2007). The measure of electrical activity is very useful for recording a short period of time, and is relatively inexpensive to purchase and run with computer-based equipment (Corr, 2006). ECG provides a thoracic interpretation of the electrical activity of the heart over time, captured and externally recorded by skin electrodes. As with skin conductance activity, the ECG and GSR are always used as the dependent measures in human studies of the effects of the awareness of stimuli. These two measures are useful for detecting physiological

responses elicited by stimuli presented below the threshold of conscious aware- ness (Corr, 2006). The measure of skin conductance response from GSR and heart rate from ECG can provide important information that is not obtainable either by a self-rating scale or by other behavioural or physiological methods (Andreassi, 2007). Another possible physiological measure for anxiety is cardio- vascular activation, which is often related to emotional responses (Faraco et al., 2003). The patterns of cardiovascular activation (blood pressure or volume) differ between the major categories of emotions (Andreassi, 2007). The device for blood pressure is becoming miniaturised, and is able to obtain accurate blood-pressure measurements. However, it is less appropriate for recording short periods of phys- iological responses. It requires one minute for the rest period recording, around 20 seconds for measuring, and another one minute for the recovery period (Lang et al., 1994). Moreover, it has a limitation in assuming the level of anxiety from other emotions. Sinhaet al. (1992). demonstrated that feelings of anxiety, action and joy produced similar blood pressure levels in diastolic readings (Sinha et al., 1992). For these reasons, blood pressure was not selected as an outcome measure. The research presented in this thesis utilised an electrical activity recording device (Figure 3.12) for heart rate and skin conductance response, in order to obtain data for short periods of time and to enable visual charts to be monitored in real-time. This allowed us to determine the severity of anxiety during the period of the virtual social-simulation exposure.

3.4.1.1 Heart Rate

A number of methods can be used to measure heart rate. The oldest of these is the pulse, which is commonly taken at the wrist and measures the number of beats of the radial artery. In the aspect of measuring anxiety, pulse rate is related

Figure 3.12: A Bio-amplifier for the Measure of HR and SCR

to physical activities rather than anxious mode, because the heart is accompanied by breathing. Universal findings suggest that pulse rate increases during a state of anxiety, although it is difficult to determine the level of anxiety with an actual rate (e.g. does a pulse rate of 90 bpm necessarily indicate that the person feels anxious?) Thus, this research only observed the increment of pulse rate from the normal state (Baseline) to determine the symptoms of anxiety (Equation 3.1):

P R−b=αP R−Baseline (Equation3.1)

, where

PR-b is the increase rate of pulse beats per minute, αP Ris the mean of pulse beats per minute,

Baseline is the mean of baseline recordings of pulse beats per minute.

In order to obtain the physiological signal for pulse rate, Contact Precision Instruments’ amplifier (www.psychlab.com) was employed. The device was es- tablished to acquire the samples in two sec epoch time with the rate of 1000 Hz, buffer byte at 1024Kb, and 50% of graphic speed. The pulse rate was recorded with a pulse transducer attached to an index finger. Customised analysis software (psylab 8.0) was applied to pre-process the data and to remove movement-related

artefacts. The average of pulse beats (bpm) was calculated to indicate subjective anxiety level.

3.4.1.2 Skin Conductance Response

Skin Conductance Response (SCR) was used as another anxiety measure in this study. Together with pulse rate, SCR is often used to indicate the symptoms of anxiety. Although individuals with anxiety disorders have generally higher SCR than non-anxious individuals, the use of SCR as a single measurement for anxiety is risky, because an anxious person’s sweating may not be connected to the need to control their body temperature, as it would be for a non-anxious person (Tyrer, 1999). Taking the same approach as the measure of pulse rate, this research observed the increment of SCR from baseline recordings to determine the symptoms of anxiety (Equation 3.2). The mean of baseline recordings of SCR was measured together with pulse rate before the participants were exposed to the VR simulation. For the baseline recording a piece of calm music (Final Fantasy Piano IX: Melodies of Life) was used.

SCR−b=αSCR−Baseline (Equation3.2)

, where

SCR-b is the increase rate of SCR per minute,

αSCRis the mean of skin conductivity startle responses per minute,

Baseline is the mean of baseline recordings of skin conductivity startle responses per minute.

In order to collect the data for the sweat response, a bio-amplifier was utilised (the same device used for measuring heart rate). The activity was recorded with two electrodes attached to the medial phalanges of non-dominated fingers. The

amplifier was set up with DC mode, 5 µmhos/ν and 0.5 Hz (subject’s baseline return to 0 - 1sec). Among various possible measures for conductance units, the level of conductance changes (SCL) during a given period of time was recorded. The recorded data was manually manipulated to eliminate artefacts, and after that the data was analysed to determine the degree of anxiety.