The body has various feedback systems. The five senses of hearing, smell, taste, vision and touch along with proprioception and vestibular input make up the body’s sensory processing system. Proprioception refers to receptors in the joints, muscles and tendons – which gives feedback about joint position and joint movement. (Where are my body parts in relation to each other and what are they doing?)
Vestibular input is the effect that movement has on the balance system of the inner ear. The ear has 3 semi-circular canals filled with fluid. These canals are situated at right angles to each other and register rotational movement. The otolith organs are basically calcium carbonate crystals resting on a bed of hair cells. These structures register gravity – linear movements and tilting movements. The feedback from the whole vestibular system together with visual input from the eyes, merge in the brain to create balance reactions and to orient the child in space.
Vestibular feedback is essential for static posture control and postural control during movement. It is also vital for eye movement control. It keeps the eyes and the head steady for function. The vestibular system has a major effect on spatial awareness: Where is my head in space and what is it doing? And where am I in relation to my environment? This awareness is the most basic, fundamental aspect of being.
Movement stimulates the vestibular system – that is movement of the head in space. Different types of movement would be: Linear movement, rotation movement, tilting, being upside down and combinations of these. This means rocking a baby, toddlers swinging, running, crawling, jumping, cycling, rolling, climbing, etc. Spinning has the most powerful impact on the vestibular system.
The vestibular system should be stimulated, but also needs to be able to modulate input. Modulation acts like a filter so that all input is not perceived as ‘too loud’ and chaotic. When the vestibular system is not being stimulated enough, or becomes overstimulated too easily, the whole system becomes affected in interesting ways. Overstimulation can result in what can be perceived as tantrums, and fatigue. One episode of even mild stimulation – beyond what a child can tolerate – can have an effect for up to 8 hours. Which means an extremely tired, cranky child.
In childhood, vision cannot develop optimally without healthy vestibular input. Those two systems are inter-related and depend on each other for input.
If children have repeated ear infections in early childhood, it affects their motor development. They may present with delayed milestones, it slows their balance reactions and development of higher postural reflexes. These postural reflexes replace the primitive reflexes seen as a baby. Retained primitive reflexes have significant adverse effect on children, especially as they reach school age and reading and writing skills become affected. Ear infections also adversely affect the vestibulo-ocular reflex. This reflex maintains vision during rapid head movements. A stable gaze is necessary for development of adequate gross and fine motor skills, as well as reading and writing skills in school.
Improper vestibular function creates physical uncertainty in terms of orientation of the child in space. Such uncertainty creates anxiety and will negatively influence emotional self-regulation, social interaction and performance in school. Children with vestibular challenges struggle to manage their own self in various situations, without the added stress of needing to perform skilled activity. This leads to frustration, fatigue and emotional upset. Vestibular input also has an effect on brain areas relating to digestion – picky eating can be the result.
The fallout of improper vestibular function is often only detected in school, when children fail to present the proper skills. Unfortunately it is often misdiagnosed or sometimes goes completely unrecognized. Some children with amblyopia (lazy eye) present with a head turn. There are various ocular factors causing this. These visual impairments are addressed by behavioral optometrists or vision therapists. Other factors contributing to head turn in children could be unilateral vestibular disturbance, improper head-on-neck proprioceptive feedback, retained Asymmetric Tonic Neck reflex (ATNR), or other underlying anxiety related issues. Children with learning challenges or lack of proper motor skills should always have a vestibular assessment. Occupational therapists address vestibular challenges and integration.
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