Perceptual Functioning Chemical Senses: Reflections on Cognitive Features influencing the central chemosensory process

Smell and taste are important parts of the sensory system that are imperative in food and nutrition selection for sensory and hedonic experience of food for fast and healthy metabolism in order to live a quality life. The olfactory and gustatory systems show variety in the mechanism of transduction and in the last ten years, there has been a lot of progress towards understanding of the main mechanisms of smell and taste. The understanding of functions of normal chemosensory organs has helped in clearing the molecular actions that highlight the disorders of smell and taste. More than two million Americans have chemosensory disorders and the numbers are growing along with the population. The disorders of smell are more common than the taste disorders because of the anatomical difference in the olfactory system. This is because a fall in the olfactory function is a part of aging. The common complaints of olfactory and gustatory are because of the number of medications and interventions for the respiratory infections of the sinus disease and the paranasal and nasal and the damage to the peripheral nerves which supply smell and taste. Most of the complaints of chemosensory have causes that are identifiable. The diagnosis of smell and taste disorders have improved vastly over twenty years, the treatment, however, is still limited of the reversible and discernible causes. Further research is still required to understand the mechanisms of chemosensory and establish the procedures of diagnosis as well as spread awareness to the people (Spielman, 1998).

The focus related to flavor is parallel to the ecological approach and Gibson (1966) argues that the main purpose of perception is to look out for the objects in the environment especially the ones that are important in the biological way. So the psychological origination of sensory data is not much salient as that data can be utilized for identification of objects. So successful perception is the one in which the sensory data is decoded as the qualities of the object. In this way, flavor is a different sense on functional basis which is constructed from psychologically distinct integration known to be the sensory system like gustation and olfaction (Prescott, 2012).

Chemical Interactions and Integration

The cross modal integration of sensory system is mostly inferred from modality responses. This is commonly an embellished response to the information that is received from a sensory system (Calvert et al., 1999). For example when a person is in a noisy surrounding, the comprehension of speech is better if the listener sees the lip movement of the speaker. So much so, the information related to the work also increases the neural response to the augment behavior and stimuli performance. There is also evidence that the odors and tastes when combined together as one flavor, they interact to change the perception of each other (Prescott, 2012). The most recognized expression of taste and odor flavor is the most observed quality that is usually inferred with the taste and odor qualities. For example when a person is asked to explain the smell of vanilla or caramel, they state that it 'sweet smells.' Similar to that vinegar is described as sour (Stevenson & Boakes, 2004). In a detailed character analysis of different smells, 65% of the participants chose 'sweetness' as an appropriate character of vanilla, while 33% stated 'sour' for hexanoic acid. All these descriptions seem similar to synesthesia in which on sensory modality elicits a consistent stimulus in another modality (Stevenson et al., 1998; Martino & Marks, 2001); while in other modalities, synesthesia is not a common action and the qualities of taste by the smells is mostly universal (Prescott, 2012).

Attentional Processes in Binding

Although the sniffing qualities of the person to enhance the taste are highly linked, like the sweet smelling smell that can embellish the sweetness of sucrose (Stevenson et al., 1999). This was seen in the findings if the smell enhances taste and Frank et al., (1993) found out that even though the smell of strawberry enhances the sweetness of sucrose when the participants were asked to recognize the smell, the embellishment was not evident enough when other abilities of fruitiness and sourness were rated (Prescott, 2012). The sweetness of the strawberry and sucrose mixture in addition was contracted when the total intensity was subjected and the responses were partitioned to salty, sweet, bitter or sour tastes. The same effects were also seen in the mixtures of tastes with similarity of judgment in the mixtures of sourness...

1993). So less sweetness was there in the subjects when they were rated (Prescott, 2012).
An important consequence of taste and odor behavior has been the integration of perception in which the smelling and tasting increases the tolerance of pain (Prescott & Wilkie, 2007). The affect was not seen to be similar and pleasant and it was concluded that the sweet smell did not act equal to the taste. The scholars assume that the effects have the same result because they have the same learned integration which produces the smell and have the quality to change the perception of taste, but there is also a demonstration which has to be carried out yet. It also shows the broader representation of the flavor as well as hedonic and perceptual results (Prescott, 2012).

Receptor cells: a new appreciation for specialization

The receptor cells of chemosensory organs are combined together with protein receptors that combine the odorants and tastants. Every receptor cell of the chemosensory system expresses a unique gene or genes which specify the selectivity of the chemical. One of the main rules of the coding is that every receptor cell is activated typically by different chemical ligands (Katz, et al. 2008). The olfactory accessory system seems not to be included in this, however it is in the main taste system and it was thought originally that all the receptor cells only respond to a single ligand (Zufall & Leinders Zufall, 2007; Dulac & Wagner, 2006; Scott 2005). It has however recently been cleared that some receptors are particular about the chemical ligands even in the olfactory system and the taste system. These receptor cells might have evolved to make sure that there is a high detection discrimination and sensitivity within the chemicals. Similarly, disrupting the receptor cells can cause a big impact on the behavior outcomes, an example of which is the human smell receptor for androstadienone and androstenone. These come from the steroid hormones that are found on urine and sweat (Wyart et al., 2007).

Early events in central processing: gating receptor input to the brain

Receptor cells start sensation, but the sensory perception of the humans also depends on the inputs processed by the brain. The initial work for this process starts at the presynaptic terminals where there is signal propagation and the neurons can be done by the presynaptic receptors which suppress the release of neurotransmitter. Different studies have demonstrated the efficient role of sensory processing in the fly and mouse olfactory system (Katz, et al. 2008).

Licks and sniffs: active sampling of the chemical environment

The smell and taste sensors are active modalities and the terrestrial vertebrates engages they chemical environment by sniffing, salivating, chewing and licking. An insect spreads its proboscis into the tastant, and then pumps it into the pharynx and tests the smells by sniffing with their antenna. Different researches have stated that the chemosensory works in their brain is shaped through the samples of repetition (Katz, et al., 2008). The sensory perception also modulates the behavior of sampling which modulates the perception and neural activity. So, the chemosensation evolves at the neuron and perception level. While in the perception of taste, the licking brings the tastant sample in the mouth repeatedly, which produces patterns in gustatory cortex (de Araujo et al., 2006; Stapleton et al., 2006).

Conclusion

The studies mentioned show the difference and variety in the approaches of chemosensory process study. During all this, some of the themes have come out that single out all these studies into one. One of those themes is the important role of the receptor cells; even though the chemosensory receptor cells are tuned for broader reception, some are very particular. This also represents the mechanism for getting out information about the features of the chemicals of taste and smell. Furthermore, the receptor cell also represents a main point of the signals which gates the input to the brain and also is an important chemical perception (Katz et al., 2008). So, the main features of chemical processing take place early in the system. It would be interesting to know in the future how these processes can be manipulated to affect the process of chemosensory behavior and perception. The other theme is that high features of cognition influence the early stages of the process as well. The neural correlations of value, expectation, difficulty, attention and alertness are observed in the initial stages of the system. They reflect the changes in the judgment of perception while sampling the behaviors. One of the…