Introduction to the Sensory Systems

Background

Outdoor play offers a valuable opportunity to develop sensory and motor skills, which lay the foundation for the progression of more developed perceptual, academic and social skills.  

  • What is Sensory Processing? 

Sensory processing (sometimes called ‘sensory integration’ or ‘SI’) is a term that refers to the way the brain receives messages from the sensory receptors and turns them into appropriate motor and behavioural responses. 

Some individuals with sensory processing differences have difficulties with modulating the input from one or more of the sensory systems.  They may be over or under responsive to the typical amount of sensory input in the environment, such as displaying heightened responses to noise or certain textures, or not responding to noises the rest of us would typically respond to. 

The other aspect of sensory processing relates to perception and discrimination of sensory input.  Sensory perception and discrimination difficulties relate to identifying, discrimination and interpreting information from at least two sensory systems.  This is different to the sensory modulation issues that may also be present.  This area of sensory processing has an impact on co-ordination and motor skills, such as ability to find an item using touch alone, body awareness (knowing where your body is in space) or ability to respond appropriately to changes in speed or motion.  Individuals may have difficulties with postural stability, bilateral coordination (using both sides of the body together to execute a task) or poor planning and sequencing skills to complete motor tasks, such as writing or feeding.

 As this diagram shows, the development of the sensory systems is essential for the progression of motor, perceptual and academic skills.

There are eight sensory systems: visual, auditory, olfactory, gustatory, tactile, vestibular, proprioceptive and interoceptive.  For more information, follow this link.

As illustrated in the pyramid diagram, there are three sensory systems which are recognised as having particular importance in development.  These are sometimes referred to as the ‘power systems’ and are the vestibular, proprioceptive and tactile systems.  Outdoor activities which provide input to these systems will support the development of skills essential for participation in all daily activities, for example, handwriting, dressing and participation in sports. 

Many autistic children and young people have differences in how they process and respond to sensory input to all sensory systems, and this then has an impact on fine and gross motor skill development.  Active participation in outdoor play offers the opportunity to give input to the sensory systems, which then improves the sensory motor skills which are prerequisite for daily functional activities.

  • The Power Systems in outdoor play

Tactile system (touch)

Location

Tactile receptors, which pick up information from touch, are located all over the skin.  There is a high concentration of receptors in the hands, providing precise information about objects and hand grasp.

Functions

  • Protective – detects pain and so protects the body from risk of injury.
  • Discriminative – processes information about the properties of objects and materials e.g. size, shape, texture. 

Importance in development

  • Pain awareness

The tactile system, along with the interoceptive system, detects pain, and this information is stored to ensure that the experience is not repeated.  Feedback is given to the brain so that motor plans are altered to ensure the activity is carried out more successfully the next time. This is how a child learns to refine their motor responses so that they can carry out activities more safely and competently. 

Example: If a child jumps off a roundabout and hurts himself/herself, they learn to slow the roundabout down before jumping off the next time.

  • Fine motor skills

Tactile discrimination is essential in the development of fine motor skills i.e. the ability to use the hands to carry out manipulative tasks.  The tactile system gives information about objects so a child learns how to hold them and move them e.g. fastening buttons, holding a pencil, lifting a cup.

Play experiences are therefore vital in giving the children the opportunity to learn about practising, self-correcting and trying again.  In this way, motor skills are developed and improved.

  • Desensitising the tactile system

Many autistic children and young people are hyperreactive to sensory input, which means they have a heightened sensitivity to some textures and types of touch.

Engaging in outdoor play offers the opportunity to explore different textures in a natural setting.  This can then reduce sensitivity and may generalise to improved tolerance of tactile input in other activities.

Example: Sand play

Using spades, containers etc. means that the child can initially avoid touching the sand directly, but over time, as he/she becomes more exposed to the sand, tolerance of the tactile input often increases.  This can then generalise to increased tolerance of other texture in daily activities, such as water (when getting washed) and wearing different clothing.

When a child or young person is hyperreactive to tactile input it is important not to force any of these activities, but to instead offer consistent opportunity for this type of play in a fun and motivating way.  The child or young person should always be able to stop the activity if feeling uncomfortable or upset by the input.

  • Development of fine motor skills

Opportunities to engage in tactile play are important for building tactile awareness throughout the body, but most importantly within the hands for the development of fine motor skills:

  • Hand strength
  • Development of grasp patterns
  • Fine manipulation
  • Bilateral coordination (using the two hands together in a coordinated manner)

Outdoor play experiences are essential for giving feedback about fine motor skills and how to adjust motor patterns to achieve tasks.

Outdoor play therefore contributes to the foundation development of fine motor skills, which in turn are essential for all daily activities, including:

  • Handwriting – pencil grip
  • Scissor skills
  • Dressing (fastening buttons, tying laces)
  • Personal care activities e.g. squeezing toothpaste onto a toothbrush
  • Using cutlery
  • Opening containers and packets

Outdoor activities for the tactile system

  • Messy play

Exploring different textures provides important tactile input which increases tactile awareness and improves discrimination.  It can also reduce tactile sensitivity through natural exposure to tactile input in fun and engaging activities.

  • Sand and water play
  • Gardening – digging, planting seeds, pulling out weeds, picking up leaves
  • Searching for bugs and minibeasts in grass and mud
  • Searching for sticks, leaves and flowers
  • Drawing on the ground with chalk
  • Painting on fences and walls (where allowed!)
  • Making bird feeders – feeling different types of bird seed
  • Barefoot activities
  • Walking across different surfaces barefoot
  • Creating sensory paths with different textures e.g. sand, grass, mud
  • Filling trays with different materials (e.g. water, paint, rice lentils) and exploring in bare feet.  Less mess to clear up when outdoors! 
  • Play activities
  • Climbing frames, ladders and monkey bars will develop grasp patterns and strength
  • Static activities (e.g. sitting on a swing, holding on to a zip wire) are less challenging, but will still provide tactile feedback, and increase grasp strength
  • Crawling and wheelbarrow walks increase tactile feedback and hand strength
  • Ball games provide tactile feedback and improve grasp and strength. Use different sizes, shapes and textures when playing ball games
  • Seasonal play
  • Winter – exploring frost, ice, snow
  • Spring – finding flowers, lifting grass cuttings, planting seeds and bulbs
  • Summer – water play, filling paddling pool with water or other textures
  • Autumn – exploring leaves, finding conkers, making bird feeders
  • Gardening
  • Planting seeds
  • Digging – with hands and/or spade
  • Weeding
  • Lifting leaves

Vestibular system (movement and balance)

Location

Receptors for the vestibular system are located in the inner ear, with one in the left ear and one in the right ear.  Different types of receptors detect different types of movement (i.e. linear or spinning).

Functions

  • Detects the pull of gravity.
  • Detects the speed and direction of movement.
  • Influences bilateral coordination (using the two sides of the body in an integrated manner).

Importance in Development

  • Balance

The vestibular system influences equilibrium responses, ensuring that we keep our balance, even when the surface under us may be unstable.  These finely tuned responses allow us to keep our balance when walking on uneven surfaces, or when the surface suddenly changes (e.g. walking along a concrete path and then onto grass).  It also allows us to keep our balance when we shift positions (e.g. stretching to lift an item from a high shelf; reaching across a desk to get a item when seated).  Balance and equilibrium responses are essential for postural control when seated, standing, walking/running and engaging in all sports.

  • Muscle tone and strength

The vestibular system processes information about gravity, influencing core muscles to extend against gravity.  In early development, this is seen in babies who extend their backs and necks to lift their heads when lying on their stomachs.  This develops muscle tone and strength, which continues throughout development as infants learn to sit, crawl, stand and walk.  All these developmental steps create the muscle tone and strength required for participation in daily activities. Postural control and stability facilitates participation in fine motor activities, such as handwriting and other tabletop tasks, as well as participation in gross motor activities, such as sports. 

  • Speed and direction of movement

The vestibular system detects the speed and direction of movement and provides feedback to the brain, which then ensures the body moves correctly through the environment.  This allows us to change direction to avoid obstacles (e.g. prevents bumping into furniture) and informs us when to speed up or slow down (e.g. running faster to catch a bus; slowing and stopping before we bump into someone in the playground).

  • Bilateral coordination

The vestibular system enables the two sides of the body to work together simultaneously in a coordinated manner, referred to as bilateral coordination.  In early development, bilateral coordination is seen in crawling and eventually walking.  As development continues, it is essential in most daily activities, including tying laces, using cutlery, stabilising paper with one hand while writing with the other and holding a toothbrush on one hand while squeezing on toothpaste with the other.

  • Regulating responses to movement

Some children and young people will have unusual responses to movement.  Some may be hyperreactive to movement, creating a fear of some types of movement, especially backward movement, spinning, fast movement, sudden changes in direction or having their feet off the ground.  This extreme response may be referred to as gravitational insecurity.  It is important that children and young people are encouraged to participate in movement activities as it develops all the skills listed above.  However, due to the extreme fear response, movement must be of the type which the person can tolerate.  It is usually best to introduce activities in which the child is firmly on the ground (avoid swings, climbing frames, etc.) and the movement should be linear in the vertical plane (e.g. jumping).

Other children and young people crave movement input, and the provision of this input can facilitate improved attention, engagement and emotional regulation if provided in the correct way.  They often respond well to fast movement, but it is usually advisable to integrate this with proprioceptive input (see next section) for optimal regulation. 

Outdoor activities for the vestibular system

  • Bilateral activities
  • Star jumps/jumping jacks
  • Crawling e.g. through tunnels
  • Wheelbarrow walks
  • Climbing up a ladder, rope or climbing frame
  • Monkey bars
  • Throwing/catching a ball with two hands
  • Riding a trike, bike, scooter or go-kart
  • Controlling speed of movement
  • Playground games, such as ‘What’s the Time Mr Wolf’, ‘Red Light, Green Light’
  • Team games, such as football
  • Changing direction
  • Obstacle courses e.g. in/out cones, changing direction to avoid obstacles
  • Dodgeball
  • Tag
  • Activities for balance and postural control
  • Jumping/hopping on the spot
  • Hopscotch
  • Walking along lines on the ground (e.g. drawn with chalk or painted); walking tiptoe or heel-to-toe
  • Walking along low walls and balance beams
  • Riding a scooter or bike
  • Bouncing on space hopper
  • Walking barefoot on changing surfaces e.g. grass, sand, mud
  • Walking/running with beanbag balanced on head
  • Egg and spoon race
  • Outdoor equipment which provides movement (vestibular) input
  • Seesaw (vertical movement)
  • Trampoline (vertical movement, but can be used for increasingly challenging movements)
  • Standard swing (horizontal movement)
  • Nest swing (movement in all planes)
  • Roundabout (spinning/rotary movement)

Proprioceptive system (body awareness)

Location

Sensory receptors for the proprioceptive system are located in the muscles, joints, ligaments and tendons throughout the whole body.  

Functions

  • Provides body scheme i.e. position of body, and how body parts are located to each other.
  • Provides constant feedback on body scheme as the person moves and changes position.
  • Controls grading and force of movement.
  • Regulates sensory input across all sensory systems.

Importance in Development

  • Awareness of body position and movements

As the proprioceptive system is located in all muscles and joints, it provides constant feedback to the brain on how the body is positioned.  Even when sitting still, the proprioceptive system gives information about where arms and legs are placed and whether or not the body is sitting upright or slouching.  Once the person is moving, more feedback is given about how body parts are moving, and this combined with the visual and tactile systems ensures that we can move through an environment without bumping into obstacles or tripping over objects.

In early development, the proprioceptive system helps the infant to understand their body scheme and body movements.

  • Grading and force of movements

Information from the proprioceptors in muscles and joints gives information about how much force is being applied by the body (e.g. how tightly an object is being held, how hard a ball is being thrown), and then adjusts force/pressure accordingly so that it is appropriate for the activity.  

  • Sensory regulation

The proprioceptive system has a regulating influence across other sensory systems.  This means that if a child or young person is feeling overwhelmed by noise, movement or visual input, they may feel calm when proprioceptive input is received.  This is why deep pressure input (e.g. massage, weighted items) can be calming, and activation of the muscles (e.g. weightbearing, climbing, stretching) is also calming.  Additionally, children and young people who crave sensory input to increase their alertness often find that proprioceptive input can increase attention and arousal levels.

Outdoor activities for the proprioceptive system

  • Weightbearing activities
  • Crawling e.g. place a beanbag on child’s back and they crawl along grass to take beanbag to a target.
  • Wheelbarrow walks.
  • Animal walks e.g. spider walks, crab walks.
  • Gymnastics
  • Resistance activities
  • Hitting ball with bat
  • Throwing/catching heavy ball
  • Tug of war
  • Climbing
  • Ladder, climbing frame, monkey bars
  • Obstacle courses
  • Through tunnels, under blankets, in/out cones
  • Gardening
  • Digging
  • Raking and lifting leaves
  • Pushing wheelbarrow
  • Lifting grass cuttings

These outdoor play activity cards contain ideas for engaging the sensory power systems.