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Home , Taste

The importance of having 'Good '

The power to change the lives of persons with deafblindness around the world

David Brown, from California Deafblind Services, continues his very successful series of articles about the and how they interact

aste (the gustatory are distributed over the (the fifth ) is the sense that , the soft , cranial nerve) in the Tdrives our , and and the laryngeal and oral and the oral cavity. Facial also protects us from poisons. . The taste receptors palsy results from trigeminal The senses of taste and are sensitive to chemical nerve damage so is likely to smell are very closely linked, stimulation provided by involve some compromise to although stimuli through substances dissolved the full and effective sense each of these senses travel in in the . of taste. We know that in by very different neurological Many nerves are responsible the population of children routes to reach the for transmitting taste with CHARGE Syndrome, for and provide information information to the brain, and example, about 43% have about environmental because of these multiple damage to this fifth cranial events and factors. Previous neural pathways a total nerve, which must present an visual, auditory and tactile loss of taste is very rare. additional, taste, difficulty to experiences can become Alongside distinctive and their other challenges with poweriully attached to identifying taste information eating and drinking. certain taste sensations and (for example, that Infants experience taste memories, and can stimulate we might refer to precisely sensations before birth as strong taste anticipatory as 'banana' or '' or the first taste buds appear expectations. 'Parmesan '), there at about 8 weeks gestational The taste receptors, are less specific and more age, and a foetus sucks and located in small areas called generalised aspects of taste swallows up to 1 litre of taste buds, are distributed sensations (those responding amniotic fluid every day, so at throughout the mouth, right to stimuli from the skin the time of birth a functional down to the oesophagus. surface such as stinging, sense of taste is already The tongue has the most burning, and chilling) well-developed. Newborn of these receptors, about which can be induced by infants have a high level of 65% of them, but the rest many through the discriminatory taste because they have a great number of taste buds (about 7,000), ' Many nerves are responsible for transmitting and the number actually taste information to the brain, and because of continues to increase for a period after birth. But the these multiple neural pathways a total loss of effectiveness and the number of the taste buds decreases taste is very rare with advancing age, so that a 60 year old person probably

4 • Dbl Review • JANUARY - Ju'lr 2008 has only about 2,000 of them to dehydration, can suppress the Japanese for a long time remaining. You may have the effectiveness of the sense but has only recently been experienced older people of taste. This dryness can also recognised in Europe and complaining about the be a common side effect of a the US, where we used to increasing blandness of foods number of medications (for think there were only four and needing more or example antidepressants, or taste groups; it's the taste of or in their meals antihistamines) and also of a {think of bacon for to stimulate their taste buds. number of diseases (such as example). Many books and Certain medications can be diabetes). articles have diagrams that responsible for taste loss and There are specific types of show maps of the should be reviewed in any taste cells that are stimulated tongue with distinct areas child suspected of having by each of the five taste that respond to each of these disturbance of the sense of groups - sweet, sour, salt, five taste groups, but now it taste. Excessive dryness of the bitter, and . This last is thought that these maps oral cavity, for example due taste has been known to are very over-simplified. Taste

JANUARY - JuNE 200s • Dbl Review • 5 sensation can be localised Glutamate (MSG) does the response even if we loved on the tongue but sensitivity same, which is why so many strong black coffee. to all tastes is distributed manufacturers use it as an across the whole tongue, additive in processed foods - So why does the sense and indeed across the other it makes us want to eat them. of taste go wrong? regions of the mouth where Bitter and sour tastes cause • Advancing age. there are taste buds, but aversive, avoidance reactions certainly some areas are more because most poisons are • Dehydration. responsive to certain tastes bitter, and food that has • Certain medications that than to others. gone bad turns sour. cause excessive dryness in The sense of taste drives Between 75% and 90% of the mouth. the appetite and protects what we think of as 'taste' is • Certain illnesses. us from poisons, so it steers actually 'flavour', which is a • Impairment or combination of taste, smell, malfunctioning of other texture and temperature senses, including smell, ' Between 75% and 90% of sensations. With the sense touch, vision and . of smell completely blocked, • Associations made with what we think of as 'taste' is for example, the sense of previous unpleasant taste becomes remarkably experiences that can result actually 'flavour', which is a ineffective (have you ever in extensive taste aversions. tried to enjoy eating a meal • Lack of use. combination of taste, smell, when you are completely texture and temperature congested with influenza?). Taste and children As infants increase their with deafblindness sensations. With the sen se experience of life they also come to associate visual So, there are obviously of smell com pletely blocked , and hearing information reasons why other sensory with taste memories, so impairments might interfere for example, the sense of that strong expectations with the effective working and associations are already of the sense of taste. Nerve taste becom es remarkably unconsciously operating for damage, especially to the even quite young children. fifth cranial nerve is also likely ineffective We can check this out to cause under-functioning for ourselves. With our of the sense of taste. Every us towards the right food noses held to block smell individual's response to taste groups and away from information, something that is very unique, and seems to the wrong ones. We need looks like cheese but tastes result from a combination , which is like a doughnut would be of experiential factors and why we like the taste of an unpleasant taste surprise, genetic makeup. In the sugar so much, and we are and produce an aversive population of children with attracted to salty tasting response like gagging and deaf-blindness there is almost foods because we must spitting, even if we actually the same wide variability of have salt in our diet. We also liked the taste of doughnuts. taste preferences that are have an need for protein, Equally, if we held our noses encountered in the rest of the and amino are the and closed our eyes and population. The exception building blocks for , heard the sound of a cork is the significant number of so the taste quality umami, popping from a bottle and children with deafblindness which is the meaty, savoury then the sound of liquid who are reported to need taste, drives our appetite being poured, all familiar very strong tasting , for amino acids. Bacon is a indicators that a glass of things like sugar, , classic food that stimulates was on its way to us, chili sauce, and salt, added to the umami receptors but then we drank and tasted their meals before they will because it is a rich source of strong black coffee, we eat them. This may reflect the amino acids. Monosodium would have an aversive taste impact of limited sensation

6 • Dbl Review • JANUARY - JuNE 200s For children with deafblindness taste and smell preferences might be more strongly linked to the motivation to eat than they are for other children, so it is important that these preferences are ascertained and respected for each child if si gnificant problems with eating and with nutrition are not to result coming in through the other What can we do to can help to ameliorate senses of touch, temperature, help? the impact of under­ smell, and vision rather than functioning taste sense, • Respect the child's taste specific damage to the taste because, in sensory terms, preferences as much sense itself. For children everything is designed to as possible, while also with deafblindness taste join up and work together. encouraging exposure to and smell preferences might a wider range of taste, be more strongly linked to texture, and temperature • If possible, consultation the motivation to eat than experiences. with a feeding therapist they are for other children, and a dietician can be so it is important that these helpful for advice on a wide • Think about the tastes of preferences are ascertained range of aspects of eating the child's current diet and respected for each child and drinking. if significant problems with and find ways to focus the child's attention on eating and with nutrition As with any sensory these, maybe by enhancing are not to result. A severely deficit, poor functioning food and drink flavors in restricted diet, for example of the sense of taste can acceptable ways, and by of liquid formula, can result be difficult to identify and keeping different foods in a very inexperienced assess, particularly when separate rather than and under-used sense of it is only a part of a wider blended together. taste, so that tolerance and pattern of sensory and other preferences can become very impairments. narrow indeed. In extreme • For children who are entirely tube fed on form, aversive responses David Brown formula, seek advice from to taste, texture, and Education Specialist a feeding therapist for temperature inputs in the California Deaf-Blind Services safe ideas to give taste mouth can stimulate choking, 1600 Holloway Avenue/ experiences which might gagging, and vomiting, so, Pacific Plaza one day help to move the again, it is important to San Francisco, CA child on to oral feeding. observe closely and interpret 94132-4201 carefully in order to build up a clear picture of the child's • Work that improves the Tel : 415-405 7559 preferences and capabilities. functioning of other FAX: 415-405 7562 sensory systems (such as Email : [email protected] smell and touch and vision)

JANUARY - JuNE 200s • Dbl Review • 7