Van Diest Ilse, De Peuter Steven, Piedfort Katrijn, Bresseleers Johan, Devriese Stephan, Van de Woestijne Karel P, Van den Bergh Omer
Department of Psychology, University of Leuven, Leuven, Belgium.
Psychosom Med. 2006 Mar-Apr;68(2):340-7. doi: 10.1097/01.psy.0000204782.49159.79.
This study aimed to investigate whether lightheadedness in response to odors could be acquired through previous associations with hyperventilation-induced hypocapnia.
Diluted ammonia and acetic acid served as conditional odor cues (CSs) in a differential associative learning paradigm. Hyperventilation-induced hypocapnia (unconditional stimulus [US]) was used to induce lightheadedness. In a training phase, participants (n = 28) performed three hypocapnic and three normocapnic overbreathing trials of 60 seconds each. One odor was consistently paired with the hypocapnic overbreathing (CS+); the other (control) odor was paired with normocapnic overbreathing (CS-). In the test phase, each odor was presented once during spontaneous breathing and once during normocapnic overventilation. Lightheadedness was assessed online during each breathing trial, which was followed by an extensive hyperventilation symptom checklist. Fractional end-tidal CO2, breathing frequency, and inspiratory volume were measured throughout the experiment.
In the test phase, participants experienced lightheadedness more quickly in response to the odor that had been paired with hypocapnic overbreathing compared with the control odor. They also scored higher on the symptom "feeling unreal."
Lightheadedness in response to odors can be acquired easily. The present results may help to elucidate the paradox that both avoidance and exposure to chemicals seem to be effective in reducing symptoms in idiopathic environmental illness.
本研究旨在调查对气味产生的头晕是否可通过先前与过度通气诱发的低碳酸血症的关联而习得。
在差异联想学习范式中，稀释的氨水和醋酸用作条件气味线索（条件刺激）。过度通气诱发的低碳酸血症（无条件刺激）用于诱发头晕。在训练阶段，参与者（n = 28）进行了三次每次持续60秒的低碳酸血症过度呼吸试验和三次每次持续60秒的正常碳酸血症过度呼吸试验。一种气味始终与低碳酸血症过度呼吸配对（条件刺激+）；另一种（对照）气味与正常碳酸血症过度呼吸配对（条件刺激-）。在测试阶段，每种气味在自主呼吸期间呈现一次，在正常碳酸血症过度通气期间呈现一次。在每次呼吸试验期间在线评估头晕情况，随后进行一份广泛的过度通气症状清单。在整个实验过程中测量潮气末二氧化碳分数、呼吸频率和吸气量。
在测试阶段，与对照气味相比，参与者对与低碳酸血症过度呼吸配对的气味产生头晕的速度更快。他们在“感觉不真实”症状上的得分也更高。
对气味产生的头晕很容易习得。目前的结果可能有助于阐明一个悖论，即避免接触和接触化学物质似乎都能有效减轻特发性环境疾病的症状。
