Human studies of brain activation:
Excerpt 1: “The brain areas activated in the present study showed some areas of similarity compared with those identified in studies of visual sexual stimulation.”
Use of fragrance for human brain activation
Excerpt 2: “In this study, we used Chanel N°5 perfume (Chanel, Paris, France) as the medium for sexual arousal in male subjects.”
Animal studies of brain activation and behavior:
Excerpt 3: “In animal studies… the median preoptic area (MPOA) of the hypothalamus, and the limbic system have been shown to be essential for sexual motivation and performance . McKenna  suggested that neurons within the MPOA, paraventricular nucleus of the hypothalamus, and the medial amygdala interact in a complex way to regulate sexual behavior in both men and women. The paralimbic areas, which consist of the inferior frontal lobe, corpus callosum, cingulate gyrus, parahippocampal gyrus, and uncus, are responsible for initiation, motivation, and goal-directed behaviors .”
My comment on the three excerpts from this article on brain activation:
Neurons within the MPOA are most likely to be collectively responsible for variations in the secretion of hypothalamic gonadotropin releasing hormone (GnRH). The role of GnRH in human sexual behavior was first detailed in a 1991 book chapter (Moss, Dudley, & Riskind, 1991).
A recent report links the likelihood of a diet-responsive hypothalamic neurogenic niche (Lee et al., 2012) to the postnatal differentiation of neuronal systems that interact with the ability of the MPOA to produce alterations in GnRH pulse frequency and amplitude in response to environmental influences (Forni, Fornaro, Guenette, & Wray, 2011). This diet-responsive hypothalamic neurogenic niche links the epigenetic effects of nutrient chemicals on GnRH to the evolution of the brain across species from microbes to man. Many other works link the epigenetic effects of pheromones to this diet-responsive neurogenic niche and to adaptive evolution of the human brain.
In mammals, GnRH pulse frequency and amplitude cause changes in the secretion of luteinizing hormone (LH). Nutrient chemicals associated with food acquisition and pheromones associated with conspecifics directly link changes in GnRH and LH from this hypothetical neurogenic niche to brain development and behaviors required for species survival in species from invertebrates to vertebrates. This direct link, via epigenetic effects on intracellular signaling that cause changes in stochastic gene expression that are linked via c-fos to GnRH (Kohl, 2012).
There is no direct link from visual or auditory stimuli that would explain any likelihood that spectral stimuli could classically condition the response to nutrient chemical associated with food odors. There is no direct link from spectral stimuli that supports the idea that spectral stimuli classically condition sex differences in responses to pheromones. The lack of the direct link from food odors and pheromones to classical conditioning of the LH response to spectral stimuli, like erotic imagery, leads to the conclusion that the response to erotic imagery is classically conditioned by olfactory/pheromonal input in precisely the same way that food odors classically condition the hormone responses associated with the visual appeal of food in men and women. Pheromones, however, are sexually dimorphic, which is why men and women respond to them differently, just as they respond differently to fragrances like the Chanel N°5 perfume (Chanel, Paris, France) used in the experiment I have just reported.