Exactly what are the taste and smell sensory systems? And how might difficulties processing taste or smell impact upon my child’s areas of difficulty?

The taste & smell systems explained

The taste and smell sensory systems work together to detect chemicals in the air and in food. This detection turns into the perception of a food, a drink or the environment – it tells us whether food is appropriate to eat, and whether the environment is a safe one.

Processing the sensory input of taste and smell requires the brain and nervous system to register and perceive information. This results in a physical and emotional response (SPD Australia n.d). The taste and smell sensory systems must be balanced in order to elicit an appropriate response and correctly enhance the perception of the food.

Taste Sensory System

Illustration by Lydia V. Kibiuk, Baltimore, MD & Devon Stuart, Harrisburg, PA

Taste buds on the tongue, at the back of the mouth and on the palate detect chemicals such as sugars, salts and acids in food (Brain Facts 2012). This stimulates nerve fibres and sends impulses along the cranial nerve to the brain stem. The impulses move through to the thalamus and cerebral cortex of the brain, giving rise to the perception of the taste.

Specialised sensory neurons in the nose detect odour molecules. These molecules stimulate nerve cells and send this information to olfactory bulbs in the frontal lobe of the brain where thoughts emerge (Brain Facts 2012). The information also moves into the limbic system which is responsible for emotion, behaviour and memory retention. It is through smell that flavour is primarily identified.

 

When the taste & smell systems malfunction

When taste or odour receptors are not detecting information effectively, difficulty in responding to sensory input arises in the form of inaccurate perceptions (Brain Facts 2012).

Sensory input may be perceived as too little (under-registration) or too much (hyper-sensitivity). These sensitivities may cause a child to become overwhelmed during meal time or other interactions, for example social events.

Sensory hyper-sensitivity frequently results in ‘fight, flight or freeze’ responses and a heightened state of arousal. Children in a heightened state of arousal may appear to react emotionally to sensations, or may refuse to engage in, or avoid, interacting in new experiences (Dunn 2014). A child with under-registration may observe to crave certain foods or tastes or fail to notice odours that others usually complain about (Dunn 2014).

A recent study indicated that children with ASD (Autism Spectrum Disorder) experience significantly more feeding problems than their peers due to sensory processing differences (Sharp, Berry, McCracken et al. 2013)

 

Recognising taste & smell processing difficulties in children

Children with difficulties processing taste and smell input often have difficulties with feeding. As a result they may present as picky eaters with a limited diet.

This table describes children’s behaviour when under-registration or hyper-sensitivity to taste and smell input are present:

A child under-registering taste input may: A child under-registering smell input may:
  • show a strong preference for certain tastes
  • crave certain foods or tastes
  • put objects in their mouth (for example, pencil or hands)
  • lack alertness during feeding
  • have long feeding times
  • overstuff their mouth
  • smell non-food objects
  • crave certain smells
  • present with a lack of alertness
  • fail to notice odours that others usually complain about
  • have difficulty discriminating unpleasant odours
A child overly sensitive to taste input may: A child overly sensitive to smell input may:
  • gag easily from certain food textures or food utensils in their mouth
  • reject certain tastes that are typically part of children’s diets
  • eat only certain tastes (for example, sweet or salty)
  • be fussy with change
  • be a picky eater, especially concerned about food textures
  • bite their tongue or lips more than other same-aged children
  • dislike or complain about toothpaste and mouthwash
  • reject certain food smells that are typically part of children’s diets
  • be offended by, or nauseated by, bathroom odours or personal hygiene smells
  • be bothered by household or cooking smells
  • refuse to play at someone’s house because of the way it smells
  • decide whether he or she likes someone or some place by the way it smells

 

(Dunn 2014)

Using occupational therapy to improve taste & smell processing

If your child is experiencing feeding challenges or problem eating, this can be addressed through the systematic desensitisation feeding program.

Therapy begins with an initial assessment to clarify your child’s challenges and identify their unique sensory profile. A therapy program is then developed based on the child and family goals and the skills and challenges to be worked on that were identified through the assessment.

The feeding program breaks down the steps involved in eating, gradually exposing your child to each step. It begins with tolerating the visual of food, then the smell, then progresses into tactile play, oral play and eating.

The program uses typical developmental steps in feeding to create a hierarchy of skills and behaviours necessary for your child to progress with eating various tastes and textures. It integrates oral-motor skills, behavioural and learning approaches, sensory processing and nutritional factors.

 

Home based activities to support development of taste & smell processing

There are plenty of ways that you can support the development of your child’s sensory processing of taste and smell input at home. These include:

  • Creating a safe, trustworthy relationship and experience during mealtime
  • Allowing for food exploration and for a mess to occur
  • Providing exposure to a variety of tastes (sweet/sour/spicy/savoury) and smells, both indoor and outdoor (like the park, beach, shopping mall, and food court)
  • Building into mealtimes a predictable routine with preparatory activities, like breathing, oral-motor exercises, and physical games providing deep pressure sensations
  • Cooking and food play
  • Craft activities using scented materials like stickers, rubbers, pencils, and crayons

Next Steps

If you think problems with your child’s taste and smell sensory systems may be impacting them and you would like to find out more about what can be done to help you can book a Startup Session below or call us on (07) 5578 2000 or to meet with one of our Senior OT’s!

References

Brain Facts 2012, Senses and Perception, http://www.brainfacts.org/sensing-thinking-behaving/senses-and-perception/articles/2012/taste-and-smell/
Dunn, W 2014, Sensory Profile 2, Pearson, Bloomington, MN
Sharp, W.G., Berry, R.C., McCracken, C. et al. 2013, ‘Feeding Problems and Nutrient Intake in Children with Autism Spectrum Disorders: A Meta-analysis and Comprehensive Review of the Literature’, Journal of Autism and Developmental Disorders, Vol 43, No 9, pp 2159-2173
SPD Australia n.d. , The Olfactory System, http://www.spdaustralia.com.au/the-olfactory-system/
SPD Australia n.d. , The Gustatory System, http://www.spdaustralia.com.au/the-gustatory-system/