School of Psychology

Which factors affect asymmetry of physiological responses to pain?

Supervisor:                  Professor Peter Drummond

Emotional influences are controlled by hemispheric specialization, and/ or painful influences on autonomic responses. This affects asymmetry of physiological responses to pain which involves the release of sympathetic vasoconstrictor and induces sympathetic vasodilatation, more so ipsilaterally than contralaterally. To investigate which influences causes asymmetry of autonomic responses, threatening instructions about cold pain to manipulate fear of pain were utilized to control participants and the cold pressor test were applied to every participants. Electrodermal activity using galvanic skin response amplifier on both palms; and facial blood flow using photoelectric pulse transducers on frontotemporal region, were measured for 56 participants (40 females and 16 males) with age ranging from 19 to 55 years old before, during and after immersion of the foot in ice water at 2º C for 1 minute. The foot was immersed three times at 4 minute intervals. Increases in facial blood flow were greater ipsilateral than contralateral to painful stimulation, for right foot stimulation (6.75 ± 7.64 % vs. -9.59 ± 7.23 %, p=.04); and for left stimulation (12.67 ± 7.23 % vs. 4.43 ± 7.64 %, p=.04). Asymmetry of electrodermal activity during painful stimulation did not achieve statistical significance. Emotional influences, manipulated by threatening instructions, rendered non-significant results in affecting asymmetry of facial blood flow and electrodermal activity. The findings supports that pain itself influences the asymmetry of physiological activity by ipsilateral sympathetic inhibition.