Yoder Wendy M, Gaynor Leslie, Windham Ethan, Lyman Michelle, Munizza Olivia, Setlow Barry, Bizon Jennifer L, Smith David W
Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL 32611, USA.
Interdisciplinary Studies Major in Neurobiological Sciences, University of Florida, Gainesville, FL 32611, USA.
Chem Senses. 2015 Jun;40(5):325-34. doi: 10.1093/chemse/bjv014. Epub 2015 Apr 15.
Response times provide essential subthreshold perceptual data that extend beyond accuracy alone. Behavioral reaction times (RTs) were used to characterize rats' ability to detect individual odorants in a series of complimentary binary odorant mixture ratios. We employed an automated, liquid-dilution olfactometer to train Fischer 344 rats (N = 8) on an odor identification task using nonreinforced probe trials. Binary mixture ratios composed of aliphatic odorants (citral and octanol) were arranged such that relative contributions of the 2 components varied systematically by a factor of 1% (v/v). Odorant concentrations for the target (S+), control (S-), and mixture (S+:S-) odorants were presented relative to threshold for each rat. Rats were initially trained to respond by licking at a spout to obtain liquid reward for either citral or octanol as the reinforced target (S+) odorant. After achieving 100% accuracy, rats were transferred to variable ratio (VR 2) reinforcement for correct responding. Nonreinforced probe trials (2 per block of 22 trials) were tested for each mixture ratio and recorded as either S+ (rats lick-responded in the presence of the mixture) or S- (rats refrained from licking), thereby indicating detection of the trained, S+ odorant. To determine the perceived salience for each ratio, RTs (latency from odorant onset to lick response) were recorded for each trial. Consistent with previous studies, RTs for both odorants were shortest (~150-200ms) when the probe trials consisted of a single, monomolecular component. Binary mixtures that contained as little as 1% of the S-, nontarget odorant, however, were sufficiently different perceptually to increase behavioral RTs (i.e., rats hesitated longer before responding); RTs changed systematically as a function of the binary ratio. Interestingly, the rate of RT change was dependent on which odorant served as the S+, suggesting an asymmetric interaction between the 2 odorants. The data demonstrate the value of behavioral RT as a sensitive measure of suprathreshold perceptual responding.
反应时间提供了重要的阈下感知数据，其意义远不止于准确性。行为反应时间（RTs）被用于表征大鼠在一系列互补的二元气味混合物比例中检测单个气味剂的能力。我们使用自动液体稀释嗅觉计，通过非强化探测试验，对8只Fischer 344大鼠进行气味识别任务训练。由脂肪族气味剂（柠檬醛和辛醇）组成的二元混合物比例设置为，两种成分的相对贡献以1%（v/v）的系数系统变化。目标（S+）、对照（S-）和混合物（S+:S-）气味剂的浓度相对于每只大鼠的阈值呈现。大鼠最初接受训练，通过舔舐喷嘴做出反应，以获得作为强化目标（S+）气味剂（柠檬醛或辛醇）的液体奖励。在达到100%的准确率后，大鼠被转移到可变比率（VR 2）强化程序，以奖励正确反应。对每个混合物比例进行非强化探测试验（每22次试验为一组，每组2次），并记录为S+（大鼠在混合物存在时舔舐做出反应）或S-（大鼠抑制舔舐），从而表明对训练过的S+气味剂的检测。为了确定每个比例的感知显著性，记录每次试验的反应时间（从气味剂开始出现到舔舐反应的潜伏期）。与先前的研究一致,当探测试验由单一的单分子成分组成时，两种气味剂的反应时间最短（约150 - 200毫秒）。然而，含有低至1%的S-非目标气味剂的二元混合物，在感知上有足够差异，足以增加行为反应时间（即大鼠在做出反应前犹豫时间更长）；反应时间随二元比例系统变化。有趣的是，反应时间变化率取决于哪种气味剂作为S+，这表明两种气味剂之间存在不对称相互作用。数据证明了行为反应时间作为阈上感知反应的敏感测量指标的价值。
