Human Pheromones:Integrating Neuroendocrinology and Ethology--论文代写范文精选

但其他哺乳动物被认为有更好的嗅觉,因为他们有更多的嗅觉受体细胞。例如,狗有大约2.3亿个嗅觉受体细胞,而人类有大约1000万。下面的paper代写范文进行详述。

Abstract 
The effect of sensory input on hormones is essential to any explanation of mammalian behavior, including aspects of physical attraction. The chemical signals we send have direct and developmental effects on hormone levels in other people. Since we don‘t know either if, or how, visual cues might have direct and developmental effects on hormone levels in other people, the biological basis for the development of visually perceived human physical attraction is currently somewhat questionable. In contrast, the biological basis for the development of physical attraction based on chemical signals is well detailed.

The human sense of smell The importance of the human sense of smell has been largely underestimated. Many people believe that human olfactory acuity and specifi city have deteriorated. Other mammals are believed to be macrosmatic (i.e., better smellers) because they have more olfactory receptor cells in their nasal mucosa than humans [1]. For example, dogs have about 230 million olfactory receptor cells, while humans have about 10 million. Accordingly, humans and other primates typically are believed to be microsmatic (i.e., worse smellers) equipped with highly developed powers of vision that supposedly make humans “visual creatures.” 

This concept needs reconsideration since many recent studies have shown that olfaction plays a very important role in human reproductive biology and because human reproductive biology affects human behavior. The nasal mucosa can functionally be divided into two areas: the respiratory region and the olfactory region, which contains the sensory cells. In the nose, the olfactory region can be found on both sides of the nasal septum in the upper nasal conchae. The ability to discern between many different odors suggests that specifi c receptors exist in the sensory cells. Excitation of axons from these sensory cells occurs when an odor molecule “docks” with a receptor protein in the membrane of the olfactory ciliae. 

It is not yet known whether the human ability to distinguish between thousands of different scents is caused by the number of specifi c receptors or by the simultaneous stimulation of multiple receptors [2, 3]. It is suspected, however, that our superior cognitive power allows us to better use olfactory input when compared with other mammals [4]. The axons of the sensory cells enter the olfactory bulb. Sensory input is then projected via the olfactory tract into the olfactory lobe of the brain. From here, olfactory input is projected via the thalamus to the neocortex and to the limbic system. This pathway allows olfactory stimuli to be consciously detected and interpreted, but also allows olfactory stimuli to directly infl uence the neuroendocrinology of emotions. The ‘affective primacy hypothesis’ [5] asserts that positive and negative affective reactions can be evoked with minimal stimulus input and virtually no cognitive processing. Olfactory signals seem to induce emotional reactions whether or not a chemical stimulus is consciously perceived. We theorize that the importance of human non-verbal signals is based upon information processing, which occurs in the limbic system, and without any cognitive (cortical) assessment. Affect thus does not require conscious interpretation of signal content. Underlying this fact is that affect dominates social interaction and it is the major currency in social interactions [6].

Affective reactions can occur without extensive perceptual and cognitive encoding. They are made with greater confi dence than cognitive judgments, and can be made sooner [5, 7]. Olfactory input from the social environment is well adapted to fi t such assertions. For example, chemical cues allow humans to select for, and to mate for, traits of reproductive fi tness that cannot be assessed simply from visual cues. The universal nature of emotional expression in different species strongly suggests the shared evolution and the fundamental nature of affect. Affect is clearly primary to language in phylogeny. Affect comes before our evolved language and our present form of thinking. Many studies have shown that the contribution of affect to signal recognition and processing has been underestimated [8, 9, 10]. 

Despite agreement that the affect-cognition question is important to research in non-verbal behavior, there are still many questions that current data do not answer. In contrast, the affect of pheromones on our emotions is linked to the effect of pheromones on the hormones of the hypothalamic-pituitary-gonadal axis – an unconscious affect. The ontogenetic link between olfaction and hormones becomes evident in patients suffering from X-linked Kallmann’s syndrome. They show underdeveloped gonads, completely lacking secondary sexual characteristics, and both male and female patients are anosmic, which means they are unable to detect odors. This syndrome results from underdevelopment of the olfactory bulb in the embryo. Gonadotropin releasing hormone (GnRH) neurosecretory cells of the hypothalamus originate in the olfactory placode and migrate into the hypothalamus. However, in Kallmann’s syndrome this migration does not occurand this is accompanied by underdevelopment of the olfactory bulb and minimal, if any, secretion of hypothalamic GnRH [11]. 

Preliminary evidence suggests that people with Kallmann’s syndrome do not respond to putative human pheromones [12]. Further to our discourse on affect, which includes the effect of human pheromones on hormones like GnRH, and thus on behavior, is the concept that affect is conditioned in the presence of other sensory input. For example, Cooper, Parvopassu, Herbin, and Magnin [13] suggest that mammalian neuroanatomical pathways link vision and olfaction. Social-environmental odor cues, which male rats may learn to visually associate with sexual activity, can be used to condition luteinizing hormone (LH) release [14]. In fact, after minimal conditioning, an arbitrary odor ultimately will elicit a male LH response, even in the absence of odor previously associated with a female. Regardless of whatever non-olfactory sensory input is involved, the functional signifi cance of the conditioned change in LH secretion lies principally in the unequivocal demonstration that olfactory cues can activate the male pituitary-gonadal axis in a way that mimics, in every respect, the activation achieved by exposure to a female. Short-term exposure of males to females also is linked to increased testosterone (T) in rats, mice, rabbits, bulls, rams, monkeys, and humans [14]. 

From a neuroendocrine perspective, given the link between LH and T, presumably, the female odor cues that condition LH release, also condition T release, and therefore have the ability to condition human hormone responses to non-olfactory sensory input. This biologically based affective reaction links the social environment to the neuroendocrinology of behavior, and does not require cognition. Based upon a detailed mammalian neuroendocrine model, Kohl [15] proposed that LH is the measurable link between sex and the human sense of smell. Kohl [16] detailed reciprocity in olfactory-genetic-neuronal-hormonal-behavioral relationships that appear to link the nature and nurture of human sexuality. Subsequently, Diamond, Binstock, and Kohl [17] offered a more complete overview of non-gonadal, non-hormonal, infl uences on sexual differentiation and of the infl uence of sensory stimuli, especially chemosensory stimuli, on human sexuality. In this regard, the affect of chemosensory stimuli on behavior was integrated with tactile cues. Dellovade et al. [18] suggest that male pheromones and tactile cues lead to the increase they noted in GnRH immunoreactive (GnRN-ir) cell numbers which were correlated with LH modulated estradiol levels and with sexual behavior. Pairing of a neutral odor with access to a receptive female rat was shown to result in an ejaculatory preference for a female with that odor [19]. Plaud and Martini [20] recently found that the sexual arousal of human males could be classically conditioned. This was confi rmed by Lalumiere & Quinsey [21] who showed that sexual interest in human males might result from Pavlovian conditioning. 

It seems likely that odor-induced, GnRH-directed conditioning of human LH release may be used to evoke functional changes in the mammalian neuroendocrine pathways that mediate the release of T and E (estradiol), with or without visual awareness of any associated stimuli. Given mammalian models, olfactory conditioning of a GnRH-directed neuroendocrine response may lead to a change in the sex steroid hormones T and E, which would be a change that also is manifest in behavior. This neuroendocrine link between social environmental sensory (i.e., olfactory) input and the neuroendocrinology of reproduction appears to preclude any involvement of cognition. Thus, the affect-cognition question is sublimated by the effect of pheromones on the neuroendocrine system, and presumably on behavior. For example, though neuroendocrine effects were not measured, Jacob, Kinnunen, Metz, Cooper, and McClintock [22] showed through brain imaging that androstadienone has distributed effects on cortical processes and brain metabolism even when it is not detected consciously. Accordingly, this human “chemosignal” modulates psychological state without being consciously discernible as an odor (see also [23]).

51Due网站原创范文除特殊说明外一切图文著作权归51Due所有；未经51Due官方授权谢绝任何用途转载或刊发于媒体。如发生侵犯著作权现象，51Due保留一切法律追诉权。(paper代写)
更多paper代写范文欢迎访问我们主页 www.51due.com 当然有paper代写需求可以和我们24小时在线客服 QQ:800020041 联系交流。-X(paper代写)