Experimental Protocol
Five individuals trained in the Freeze-Frame (FF) [12] technique were seated in comfortable, high backed chairs, to minimize postural changes, fitted with ECG and EEG electrodes, respiration belt, and ear and finger pulse transducer sensors. Prior to each session, subjects were informed of the tasks they were to perform and asked to refrain from talking, falling asleep, exaggerated body movements or intentionally altering their respiration. The subjects were carefully monitored to ensure that there were no exaggerated respiratory or postural changes during the session. No biofeedback aids were used in this study, and none of the subjects had any prior experience with biofeedback training. The subjects were monitored, one at a time, using a 15 minute baseline period followed by a 5 minute FF period. Briefly stated, the Freeze-Frame technique instructs subjects to consciously disengage from stressful mental and emotional states by shifting attention to the heart, which most people associate with positive emotions, and focus on sincerely feeling appreciation or a similar positive emotion toward someone or something (in contrast to solely mentally recalling or visualizing a past positive experience). Previous experience with this technique has shown that it is an effective method for shifting the focus of attention away from current stressors. The conscious shifting of awareness to a positive emotional feeling state appears to be a key to the successful application of this maneuver.

Ag/AgCl disposable electrodes were used for all bipolar ECG measurements. The positive electrode was located on the left side at the 6th rib and the reference was placed in the right supraclavicular fossa. Grass model 7P4 amplifiers were used for ECG amplification. The HRV waveform is in the form of an R-R interval tachogram. The spectral analysis of this signal was obtained from the successive discrete series of R-R duration values taken from the original ECG signal sampled at 256 Hz and Fast Fourier Transformed (FFT).

The EEG was amplified with Grass model P5 amplifiers, and electrodes were attached according to the International 10-20 system at the O1, O2, FP1, FP2, CZ, T5, T6, T7 and T8 locations. The LF filters were set to the 0.15 setting. Respiration was monitored with a Resp-EZ piezoelectric belt around the chest. A Grass model 80 cardiac microphone was used to monitor the blood pressure wave for calculation of pulse transit time (PTT). The PTT interval is the time between the peak of the R-wave of the ECG and the appearance of the pulse wave associated with that same cardiac contraction at the index finger on the left hand. A UFI model 1020 photoelectric pulse transducer was used to obtain the pulse wave arrival at the right ear lobe.