Cometto-Muñiz J Enrique, Abraham Michael H
Department of Surgery (Otolaryngology), University of California, San Diego, La Jolla, CA 92093-0957, USA.
Behav Brain Res. 2009 Jul 19;201(1):207-15. doi: 10.1016/j.bbr.2009.02.014. Epub 2009 Feb 21.
We measured concentration-detection (i.e., psychometric) odor functions for the homologous ketones propanone (acetone), 2-pentanone, 2-heptanone, and 2-nonanone. Under a forced-choice procedure, stimuli were presented via an 8-channel air-dilution olfactometer that allowed natural sampling of the odorant and whose output was quantified by gas chromatography. Subjects (17-22 per compound) comprised young adults from both genders, all normosmics and nonsmokers. A sigmoid (logistic) equation tightly fitted group and individual functions. The odor detection threshold (ODT) was the concentration detectable at halfway (P=0.5) between chance (P=0.0) and perfect (P=1.0) detection. Odor sensitivity increased (i.e., thresholds decreased) from acetone to heptanone, remaining constant for nonanone. This relative trend was also observed in previous work and in odor thresholds compilations, but the absolute ODTs obtained here were consistently at the lower end of those reported before. Interindividual variability of ODTs was about 1 order of magnitude. These odor functions measured behaviorally in humans were obtained at vapor concentrations 1000 times lower than functions measured via activation, with similar 2-ketones, of receptor neurons converging into individual olfactory glomeruli of mice, visualized with calcium sensitive dyes. Odorant concentrations presented as vapors (as in behavioral studies) and those presented as liquids (as in cellular/tissue studies) can be rendered equivalent via liquid-vapor partition coefficients and, then, compared in relative olfactory potency. These comparisons can reveal how sensitivity is progressively shaped across levels of the neural pathway.
我们测量了同系物丙酮、2-戊酮、2-庚酮和2-壬酮的浓度检测（即心理测量）气味功能。在强制选择程序下，通过一个8通道空气稀释嗅觉计呈现刺激物，该嗅觉计允许对气味剂进行自然采样，其输出通过气相色谱法定量。受试者（每种化合物17 - 22名）包括来自不同性别的年轻成年人，均为嗅觉正常者且不吸烟。一个S形（逻辑）方程紧密拟合了群体和个体功能。气味检测阈值（ODT）是在随机检测（P = 0.0）和完美检测（P = 1.0）之间的中点（P = 0.5）可检测到的浓度。从丙酮到庚酮，气味敏感性增加（即阈值降低），壬酮的阈值保持不变。这种相对趋势在先前的研究和气味阈值汇编中也有观察到，但此处获得的绝对ODT始终处于之前报道的下限。ODT的个体间变异性约为1个数量级。在人类中通过行为测量得到的这些气味功能，是在比通过激活具有相似2 - 酮的受体神经元（这些受体神经元汇聚到小鼠的单个嗅觉小球中，用钙敏染料可视化）所测量的功能低1000倍的蒸汽浓度下获得的。以蒸汽形式呈现的气味剂浓度（如在行为研究中）和以液体形式呈现的浓度（如在细胞/组织研究中）可以通过液 - 气分配系数变得等效，然后在相对嗅觉效力方面进行比较。这些比较可以揭示敏感性是如何在神经通路的各个水平上逐渐形成的。
