Sensory Modulation & Tactile dysfunction

Have you ever thought why do we optimise the volume of television or brightness of our laptops and iPhones while using them during day or night? Why does professional photographer optimise his camera lens before clicking the picture or why do we adjust regulator of the oven while baking a cake?

The answer is simple, to get the best outcomes of whatever we are doing!

Tuning televison sound is important to hear properly, whereas camera lens optimisation is essential to get better picture quality results.

The way we adjust our electronic gadgets to get better results and make our lives easier, similarly our brain registers and modulates (adjusts) sensory information received from outside world according to our body’s tolerance level and comfort zone. It optimises the received sensory input due to which we react to different sensations in an appropriate manner. 

For example, on being hugged or kissed by loved ones we feel pleasurable, the smell of good food makes us feel hungry and happy or looking at flowers or fishes helps us to calm down and feel joyful.

Children with developmental delays, ADHD, and ASD often demonstrate behaviours appearing hyposensitive at one time (example: lack of body awareness or auditory input, invading other’s space) to appearing hypersensitive at other time, (example: doesn’t like being touched or hugged, dislikes for messy activities, prefers to wear long sleeves and pants). The Same child can have hypersensitivity or hyposensitivity towards touch, taste, movement or auditory (hearing) stimuli or a combination of both hyper and hypo-sensitivity. 

This fluctuation of behaviour from one spectrum to another spectrum is defined as sensory modulation disorder.

So, what happens due to Sensory Modulation disorder?

Modulation can be defined as the capacity to regulate and organise sensory input in a graded and adaptive manner. In simple terms, sensory modulation allows our brain to regulate and attend important information coming from the external world and filter out irrelevant stimuli. It enables the brain to experience pleasurable and intolerant sensations.

Consider an example of day to day life, while travelling in a public transport (tube, train or bus) we are usually distracted by the aroma of strong perfume or deodorant of person who has just boarded a train and stood next to us. Our brain system gets distracted momentarily by the fragrance of deodorant, however, within a couple of minutes, it gets adapted to smell. This happens due to modulation ability of the nervous system, which allows brain to regulate, organize and adapt the sensory input. Regulating different sensory inputs is sometimes a great challenge for children with sensory issues.

In atypically developing children the registration and modulation of sensations do not happen habitually due to which they display disruptive behaviours frequently and face difficulties while performing simple or complex tasks.

For example, a child with sensory modulation disorder may be affected by the chirping of birds outside the classroom or humming noise made by bee or background environmental sounds such as construction or vehicle passing through. The reason is auditory (hearing) hypersensitivity towards sounds which are irrelevant for others.  It is commonly observed in the classroom, these children are distracted by bright lights and colours and complain of a headache by the end of a day. 
This happens due to visual (vision) hypersensitivity. The brain does not function well and has difficulty in modulating and regulating visual input appropriately for longer periods of time. Avoidance or dislike to messy play such as sand, water, paint is an example of tactile (touch) hypersensitivity. 
Some children like chewing shirts, collar, hair or fingers due to hyposensitivity of oral (mouth) sensory processing. Some children love running around, jumping and hopping all the time, due to hyposensitivity towards vestibular (movement) sensations.

The conclusion of above-mentioned examples is sensory modulation disorder.  Each child is different and has different sensory modulation issues, therefore, identification of modulation difficulties and their intervention varies from child to child.

Children’s ability to curb and regulate sensory inputs effectively is influenced due to which they display frequent behavioural disruptions and emotional liability too. Their motor planning ability, body awareness, academic learning, emotional security and social skills can also be affected due to modulation. Noticeable behavioural changes can include anxiety, anger or depression. Moreover, poor modulation results in disorganisation, impulsivity, hyperactivity, inattentiveness and lack of self-regulation within the classroom and home setting.

Discussing Tactile (Touch) sensory system dysfunction characteristics it can be categorised as Tactile hypersensitivity, Tactile hyposensitivity or Poor Tactile Perception and Discrimination.

Tactile Defensiveness/Hypersensitivity (Over-responsiveness):

In this condition, child reacts negatively or over-responds to a touch situation which
other children find non-threating and non-aversive (usual or normal). Their brain may not gait touch sensations, so they may be sent into fight or flight over very small, everyday touch sensations. A child will not like being hugged or touched by anyone unexpectedly. These children are often distracted and hyperactive or overly active since they respond to incoming irrelevant sensory input. They might be indifferent towards self-care tasks such as using shower gel or soap for bathing, hair cutting or nail cutting. Moreover, would not prefer to get involved in messy activities or art work.

Tactile Hyposensitivity (Under-responsiveness):

Now this is the situation where the child does not feel any major changes due to temperature or the wind on their body. This is completely opposite of Tactile Defensiveness. Child under-responds to touch situations which other people may find threatening. They would not respond to injury or any hazard the way other people do. Their brain does not register and modulate different sensations of pain, temperature or pressure. 

Touching hot cup of coffee might go unnoticed by them which can lead to burning of the skin. They would repeatedly touch objects and loves messy activities with paint and un-paint.Very commonly, young kids, are unaware that their nose is running or is dirty.
This category of children can be self-harming, self-abusive pinching, biting or hitting their own head. Young children will mouth objects excessively. Bumping into objects or people with high intensity or force gives them pleasure. 
They may carve for vibrating and strong sensory input. Invading into other’s space, or preferring to eat excessively spicy food can be observed in this category of children.

Poor Tactile Perception and Discrimination:

In normal developmental process, as the child grows he develops gross and fine motor
skills ability to discriminate different fabrics (soft blanket or stuff toy and wooden surface), sizes (small and large Lego pieces). Children with tactile discrimination difficulties struggle to identify where and how they are being touched without vision or with eyes closed.

Consider a situation, your family member asks you to take off your shirt and sit on a chair. Then he/she asks you to close your eyes until he/she asks to open. You follow his/her instructions. She lightly touches on your back with two fingers and then asks where did she touch. It will tricky for you to tell where two fingers touched on your back but not impossible, the, however, the child with tactile discrimination difficulties will have the challenge to identify touch. Moreover, if they were two or three or just one finger, that will be also tough for him to identify.

We are able to put a cap on a water bottle or pen without looking at it, turn on or off television with remote control without looking at buttons or control tap water faucet while talking to a friend. This all happens due to tactile discrimination abilities. Children with sensory seeking behaviours and hyposensitivity display tactile discrimination difficulties quite often.

A cluster of behaviours should be identified before putting a child under any category of hypersensitivity (tactile defensiveness) or hyposensitivity. Identification of behaviours is professionally done by Occupational Therapist who is trained in Sensory Integration. Standardised tests such as SIPT, SPM are conducted by them to draw a conclusion regarding child’s condition.