awareness and understanding of ourselves and our environments come about through
the integration of thousands of pieces of sensory information. For example, a
boy coming home from school may enter his house and know his parents are home
because he can see the light is on, he can hear the sounds of footsteps in the
house, he can feel the warmth of the heating and he can smell something cooking
in the oven. He will not consciously register all these pieces of information,
but will form a coherent and automatic understanding of his situation.
Most people are able to take this integration of neurosensory information for granted, but other people suffer from neurosensory dysfunction. This is a weakness in the way sensory information from various parts of the body is integrated and transmitted to the brain, and may occur because the primitive reflexes present when the baby was born (to ensure the baby’s survival) were not replaced with more mature reflexes as the child became older . This can manifest as poor motor skills, learning disabilities, language or speech delay, attention disorders or emotional and social issues. Neurosensory dysfunction often occurs alongside a specific developmental disorder and will not be considered as a separate issue [74,75].
A perfectly functioning ear does not guarantee a perfectly functioning auditory system. Likewise, a perfectly functioning nose does not guarantee a perfectly functioning olfactory system. Therefore, sensory systems should not be purely thought of as abilities to hear, see, feel, smell or taste in isolation of each other. Our senses are only useful when the connections from the organ to the brain are operating normally. In addition to this, we often forget that we receive sensory information from inside our bodies .
Reflexes and sensory systems
When children are born, they emerge from the womb with primitive reflexes – physical responses that are initiated without conscious thought or intention. These reflexes allow the child to cope with the influx of new sensory information from the post-utero environment. Primitive reflexes are supposed to take the child through their first year in the world, but should then be overtaken and inhibited by voluntary actions – these are referred to as postural reflexes or postural control . Postural reflexes gain precedence through the continual movement of the child .
Where primitive reflexes come about through automatic signals from the brainstem, postural reflexes are a result of higher order processing in the midbrain. Primitive reflexes appear in the womb after 5 weeks , and should disappear between the ages of 6 and 12 months. If this does not occur a child may be experiencing neuro-developmental delay. The graduation from primitive to postural reflexes does not occur instantaneously, and there is a limited period of interplay between the two. Once the postural reflexes become more mature and are executed with less conscious intention, they become dominant in the child’s functioning .
The retention of primitive reflexes does not present clearly. One such reflex is the palmar reflex, where the fingers automatically close when the palm is stimulated. A child who has retained the palmar reflex will not demonstrate this precise characteristic at the age of 6, but instead may have poor pencil grip and trouble with fine motor coordination or manual dexterity. Each primitive reflex has its own set of consequences if it hasn’t been fully inhibited by its postural equivalent .
There are many different types of primitive and postural reflexes, all of which have direct links to sensory systems. At this point, it is important to note that the five primary senses (hearing, taste, touch, vision and smell) are not equally significant in these processes. In addition to this, there are many sensory systems and those involved in Neuro Developmental Therapy are not commonly discussed alongside the primary five .
The two most important systems are the proprioceptive and the vestibular systems. Muscles and joints transmit information to the brain about the position of the body, and this is known as the proprioceptive system. The vestibular system (in the inner ear) also detects any changes in the centre of gravity or the position of the head, and uses information from the muscles to maintain balance and motor coordination. As our muscles move, our brain makes sense of where we are and how our bodies are positioned. The reception and integration of this information is vital to healthy development .
Neuro Developmental Therapy (NDT)
Treating developmental disorders involves an assumption that effective functioning cannot exist without normal development. As a result, interventions for such disorders often target elements of the developmental process that may have been skipped altogether or not completed fully. While most developmental milestones are acknowledged through physical achievements (crawling, standing, walking), these milestones have their basis in the brain’s connections – that is, poor motor development is most often a result of neuro-developmental delay . For that reason, it makes sense to address the neurological origin of the problems .
The concept of Neuro Developmental Therapy (NDT) was devised by an occupational therapist, Dr Jean Ayers, and has been expanded through contributions by researchers in many related fields . This type of therapy is also known as Neurosensory Integration. The rationale behind it is that sensory systems and reflexes are indivisible, and that any existing primitive reflexes can be actively inhibited by exercising the postural reflexes. The major reflexes, both primitive and postural, have the effect of maintaining and controlling posture, physical actions and equilibrium. This is why NDT involves activities or tasks designed to improve these elements of functioning .
The systems targeted in Neuro Developmental Therapy are those involved in learning through motion. Motion, or movement, is detected by the tactile system, the auditory system, the visual system, the vestibular system (balance) and the proprioceptive system (body position) [59,74]. Neuro Developmental Therapy usually involves following a sequence of sensorimotor activities centred on these sensory systems. Most commonly the sequence involves energising tactile stimulation, vestibular or auditory activity, proprioceptive stimulation, a calming of the child, which is followed by fine motor activity .
All sensory systems develop with reference to the vestibular system. The vestibular system is functional by 16 weeks in utero, and sends its messages directly to the cerebellum (the part of the brain concerned with movement). Once the child is born, the other undeveloped sensory systems send their input to the vestibule for analysis and it is here that sensory integration (or sensory organisation) takes place. It is through movement that a child develops postural control as every movement stimulates specific neural connections. The more often a specific neural pathway is activated, the stronger and more automatic it becomes .
Neuro Developmental Therapy should be enjoyable and interesting for children, and aims to assist the child’s internal and external awareness . It can be thought of as a movement program that guides the child through the earliest stages of developmental reflexes . Neuro Developmental Therapy is, in a sense, the reliving of the experience of sensory development so that the primitive reflexes are revisited and overtaken as they ideally would have been during the child’s infancy.
Depending on the child’s sensory profile, Neuro Developmental Therapy programs will involve different activities to inhibit particular primitive reflexes . This profile is developed through an assessment by a qualified professional and often involves different phases of activities.