Psychology Department, Emory University, Atlanta, GA, USA.
Comprehensive Pet Therapy, Inc., Sandy Springs, GA, USA.
Chem Senses. 2020 Dec 5;45(9):833-844. doi: 10.1093/chemse/bjaa068.
In working and practical contexts, dogs rely upon their ability to discriminate a target odor from distracting odors and other sensory stimuli. Using awake functional magnetic resonance imaging (fMRI) in 18 dogs, we examined the neural mechanisms underlying odor discrimination between 2 odors and a mixture of the odors. Neural activation was measured during the presentation of a target odor (A) associated with a food reward, a distractor odor (B) associated with nothing, and a mixture of the two odors (A+B). Changes in neural activation during the presentations of the odor stimuli in individual dogs were measured over time within three regions known to be involved with odor processing: the caudate nucleus, the amygdala, and the olfactory bulbs. Average activation within the amygdala showed that dogs maximally differentiated between odor stimuli based on the stimulus-reward associations by the first run, while activation to the mixture (A+B) was most similar to the no-reward (B) stimulus. To clarify the neural representation of odor mixtures in the dog brain, we used a random forest classifier to compare multilabel (elemental) versus multiclass (configural) models. The multiclass model performed much better than the multilabel (weighted-F1 0.44 vs. 0.14), suggesting the odor mixture was processed configurally. Analysis of the subset of high-performing dogs' brain classification metrics revealed a network of olfactory information-carrying brain regions that included the amygdala, piriform cortex, and posterior cingulate. These results add further evidence for the configural processing of odor mixtures in dogs and suggest a novel way to identify high-performers based on brain classification metrics.
在工作和实践环境中，狗依赖于它们从干扰气味和其他感官刺激中区分目标气味的能力。我们使用 18 只狗的清醒功能磁共振成像 (fMRI)，研究了在两种气味和两种气味混合物之间进行气味区分的神经机制。在呈现与食物奖励相关的目标气味 (A)、与无奖励相关的干扰气味 (B) 和两种气味的混合物 (A+B) 时，测量了神经激活。在个体狗中，随着时间的推移，在已知与气味处理相关的三个区域（尾状核、杏仁核和嗅球）内测量了气味刺激呈现期间的神经激活变化。杏仁核内的平均激活表明，狗通过第一组运行基于刺激-奖励关联最大程度地区分气味刺激，而对混合物 (A+B) 的激活与无奖励 (B) 刺激最相似。为了阐明狗脑中气味混合物的神经表示，我们使用随机森林分类器比较了多标签（元素）与多类（构形）模型。多类模型的性能明显优于多标签模型（加权-F1 为 0.44 比 0.14），这表明气味混合物是构形处理的。对表现较好的狗的大脑分类指标子集的分析揭示了一个包含杏仁核、梨状皮层和后扣带回的携带嗅觉信息的大脑区域网络。这些结果为狗对气味混合物的构形处理提供了进一步的证据，并提出了一种基于大脑分类指标识别表现较好的狗的新方法。
