We are born with a sensory system that helps us survive by interpreting
information from our internal and external environment, integrating
that information into a whole picture, and developing an appropriate
response. What is this sensory process and how does it develop? We have
our five familiar senses: visual (seeing), auditory (hearing), gustatory
(tasting), olfactory (smelling), and tactile (touching) systems. There
are two other senses, often called the hidden senses, which may not
be as familiar to us. These are the proprioceptive (body awareness)
and vestibular (movement) systems. The visual, auditory, and olfactory
systems are often considered to be distal senses, meaning that information
comes to them from a distance and is then interpreted by the brain in
a series of increasingly integrative neural firings. The gustatory and
tactile systems, on the other hand, are a combination of distal and
proximal because, even though the stimulus is outside the body, the
object must come into contact with the body to be known. Because awareness
is contained in the body itself, the proprioceptive and vestibular systems
are considered to be proximal senses (meaning nearer the center of the
body). The proximal senses, particularly the vestibular system, are
considered key to one’s ability to integrate sensory information
accurately. In humans, sensory development and capabilities start in
the fifth week of gestation, beginning with touch. The perception of
pain appears in the brain and spinal column at 12 to 16 weeks gestation
(Foster & Verny, 2007).
To better understand how
our sensory system gives us a picture of the world, let’s consider
one of the five senses in detail. Our tactile system has two major purposes:
to provide protection (by telling us when a stimulus is potentially
dangerous and activating the fight/flight system) and discrimination
of input (by telling us where we are being touched and what is touching
us). This sense is the first to receive information about the world
in utero and is central in an infant’s bonding process.
When there is tactile over-responsivity,
the receptors perceive normally non-noxious stimuli as noxious or harmful,
with the result being a fight or flight response. Children may scream,
yell, and possibly run from parents who are trying to appropriately
wash their faces. They may feel easily upset by the textures of clothing
and food. At the other end of the spectrum, children who are under-responsive
may need stronger tactile input, including extra touch stimulation or
deep pressure, both passive and active, in order for them to feel calm
(Kranowitz, 2005). Such children may have difficulty getting dressed
because they cannot feel the buttons, or where the clothes are on their
bodies. In addition to these differences, children may experience difficulties
with attachment because of their altered way of experiencing caring
touch. As with all of ours senses, touch is an important link in allowing
us to integrate and respond to our experience of the world, and so is
part of several other challenges. For example, children with dyspraxia
have difficulty conceiving of, organizing, and performing activities
that involve a sequence of movements. Part of the reason for this may
be that they cannot interpret tactile information appropriately to make
an adaptive response with their bodies. Essentially, the tactile difficulty
interrupts the brain’s usual push toward integration.
Now let’s consider
the two hidden senses. Proprioception, sometimes called kinesthesia,
allows us to sense the position and movement of our body and its parts.
Sensory nerve endings in our muscles, tendons, and joints provide the
input for the brain to register the body’s position. Our awareness
of this sense generally remains below the level of conscious awareness.
Proprioception helps integrate touch and movement sensations to let
us know where each part of the body is relative to the others and how
it is moving. It allows us to be aware of our position in space and
our timing. This sense also plays a part in the process of becoming
alert or calming down. This input is also referred to as “heavy
work” because it requires us to use our muscles and joints in
order for our brains to register this input. Children with proprioceptive
dysfunction may look very clumsy and have difficulty grading the amount
of force or pressure to use when interacting with objects or people.
In an attempt to get a better sense of their bodies, they might constantly
climb or jump.
Vestibular System
The vestibular system, which gives us information about balance and
movement, is located in the labyrinth of the inner ear, just adjacent
to the cochlea. It is composed of a series of semicircular canals that
detect rotational movements and associated small sacs that detect linear
movements. Because we are almost always in both kinds of motion, imagine
the complexity of the input that has to be translated into output to
the rest of the body/brain for us to function in the world. This sensory
system responds to the pull of gravity, providing information about
the head's position in relationship to the surface of the earth. It
is also a unifying system that co-ordinates information from the vestibular
organs in the inner ear, the eyes, muscles and joints, fingertips and
palms of the hands, pressors on the soles of the feet, jaw, and gravity
receptors on the skin, while adjusting heart rate and blood pressure,
muscle tone, limb position, immune responses, arousal and balance (McAlpine,
n.d.). This has been called our most robust sensory system, as input
from this system can last four hours. As a result, part of its job is
to prime our autonomic nervous system to function effectively in the
fight-flight response as well as for self-soothing. As we would expect
with these multiple integrative functions, the vestibular system has
projections throughout the cortex and limbic areas, many of which are
not yet well understood.
Children with a vestibular
dysfunction may always be in motion, have poor balance, have poor timing
and sequencing of movements, be unable to anticipate movements in time
and space (like catching and throwing a ball, or navigating a crowded
playground), have poor ocular control, and be emotionally labile, particularly
prone to anxiety and panic attacks. Some children may also be afraid
of or over-sensitive to movement. Because of the close connection with
the auditory system and other areas of the brain, those with vestibular
dysfunction may have difficulty processing language. A growing body
of research including the work of Stephen Porges (2007) also suggests
that the vestibular system plays a significant role in Acute and Post
Traumatic Stress Disorders (which makes sense because of the close connection
with the autonomic nervous system), as well as the spectrum disorders
of Autism.
As we consider the complexity of sensory processing, we might marvel
that for most of us this continuous integration of information coming
to us through our senses (touch, smell, taste, vision, hearing, movement,
and proprioception) is automatic. We receive the information, organize
and interpret it, and make a meaningful, adaptive response. We hear
someone talking to us, our brains receive that input (along with multiple
other inputs from inside and outside our bodies), recognize it as a
voice talking in a normal tone, and we respond appropriately. Until
fifty years ago, there was no clear definition or help for children
(and adults) whose brains weren’t able to achieve this kind of
integrative functioning, often leading to frustration for parents who
couldn’t understand their children’s differences. Having
struggled with similar learning difficulties as a child, A. Jean Ayres
(1980/2005) became an occupational therapist and psychologist dedicated
to the understanding, assessment, and treatment of what she identified
as Sensory Integration Dysfunction (SID/SI/DSI), the inability of the
brain to correctly process information brought in by the senses. Her
work paved the way for a great deal of illuminating research, allowing
Miller and Lane (2000) to clarify terminology and identify subtypes.
We now recognize a range of Sensory Processing Disorders (SPD): Sensory
Modulation Disorder (SMD), Sensory Discrimination Disorder (SDD), and
Sensory-Based Motor Disorder (SBMD). These designations help practitioners
in different fields communicate with one another with clarity and precision.
In addition to behavioral and self-esteem issues, it appears that close
to 90% of the children that mental health practitioners see may have
underlying processing difficulties (Foster, 2006).
No two children or adults
will be affected by SPD in the same way. Overall, children have varying
problems with both understanding input and formulating output. SPD affects
the way their brains interpret the information that comes in; it also
affects how they respond to that information with emotional, motor,
and other reactions. As we discussed above, some children are over-responsive
to sensation and so feel as if they are being constantly bombarded with
sensory information. They may try to eliminate or minimize this perceived
sensory overload by avoiding being touched or being very particular
about clothing, or only eating certain foods. Some children are under-responsive
and have an almost insatiable desire for sensory stimulation. They may
seek out constant stimulation by taking part in extreme activities,
playing music very loudly, or moving constantly (Miller, 2007).
Some of the most significant discoveries about how to improve outcomes
have come from research with premature infants and children who have
lived in international orphanages (Healy, 2002). The care of premature
babies and newborns with traumatic pre- and post-birth histories provide
clues about how to foster sensory integration in the nervous system.
For instance, very early in development, Occupational Therapists (OTs)
working in the NICU may diagnose premature babies with Sensory Defensiveness.
The OTs help the parents understand how to relate with their babies.
Often, these preemies need a quiet environment with less sensory input.
In an effort to connect, parents often give babies too much—too
much talking, proximity, and movement. What these tiny, highly sensitive
beings need is soft, slow input that feels safe for their immature and
already-taxed nervous systems.
Through the actions and sensitivities
that support secure attachment from conception through infancy, parents
in general can help improve the outcomes for any infant. When parents
can read the cues of their infants and respond to their needs with warm
accurate care, they will be able to sense how to carry, touch, gently
move them in different directions, and generally be aware of how the
tone and pitch of the voice is being received. Research, as well as
personal observation, indicates that infants are generally wonderful
teachers for their parents, showing caregivers what they need, how much
of it feels good, and when to stop. Infants often stop crying when picked
up, which may indicate that they need the movement and/or touch/pressure
to help modulate their sensory systems; babies also look away when over
stimulated with eye contact. Some of the ways that parents can stimulate
and/or soothe their infants are by baby wearing in a sling, massaging
the body during a baby's quiet alert moments where the skin-to-skin
contact reduces cortisol and increases oxytocin, and breastfeeding,
which exercises the muscles of the tongue, lip, and jaw. In addition
to the nutritional and immune system benefits, breastfeeding also helps
stimulate all the sphincter muscles of the body cavities, including
the pupils of the eyes, which later may translate into a better capacity
to focus (Gross-Loh, 2006; Bluestone, 2006). As parents, we can provide
the safe, warm contact that encourages optimal integration throughout
the brain.
As we are learning more about how the human infant brain and nervous
system develop in the prenatal period and in the first two years of
life, we have reason to rethink some popular early childhood practices.
The need for parental support in the development of a healthy sensory
system suggests that spending excessive amounts of time in car seats,
strollers, and front-to-back infant swings may be quite detrimental.
In general, when parents have the inner resources to truly see their
children and respond accurately to their unique needs, their children’s
capacity for sensory integration can be maximized. This is true through
all the rituals of childhood: eating, sleeping, dressing, playing, relating.
For example, we know that
integration is supported when babies crawl before walking. As children
grow, they benefit from play, especially in natural environments. Just
look at some of the activities that help to develop the vestibular system:
rolling (down a grassy hill), swinging (but never forced), spinning,
sliding, riding vehicles like bikes and scooters, walking on unstable
surfaces (such as a sandy beach), rocking, riding and balancing on a
teeter-totter, balancing on a large therapy ball, jogging, horseback
riding, and swimming to name a few. Jaak Panksepp (2007) suggests that
the diagnosis of ADHD could be reduced if children in schools had more
time for recess, play, and general movement, especially on swings.
Before leaving this topic, let’s talk a bit about SPD and adults.
Many people may have had undiagnosed SPD in their childhoods, and may
have chosen lifestyles that have helped them self-correct or better
compensate for this problem. Often, adults find careers that help them
learn to live with their particular learning style or difference. For
instance, a person who needs more stimulation may wake up early to surf
in the morning, go to work in construction, and in the evening play
an electric guitar. When faced with transitions or changes to their
lifestyle, such as going back to school, managing their own business,
or changing careers, adults may have to revisit how they learn best.
It is helpful to
consider an individual's unique style of interpreting sensory information and learning style—visual,
kinesthetic, or auditory, and to be aware of any learning differences
that may have gone undiagnosed in childhood. Such interest in and understanding of the
uniqueness of our sensory experience when embraced can amplify the potential for a sense of being
seen and known by loved ones.
The discomfort of SPD often
leads adults to take steps to manage their physical and emotional universe.
Addictions may be one of the ways that adults self-medicate. Smoking
is an example. Besides the chemical addiction of nicotine, adults may
use the sucking in and blowing out of cigarette smoke to self-soothe
as well as to improve focus. Having to go outside to smoke also gives
the individual an opportunity for self-soothing by increased movement
and separation if they are feeling awkward in a social situation. Using
a silly straw for drinking, blowing bubbles with a wand, chewing gum,
or blowing out candles are similar therapeutic activities for sensory
processing dysfunction, if one craves oral input to help calm them down.
(A small caution—drinking through silly straws is not advised
during pregnancy).
Many clinicians and researchers
who had SPD as children suggest that individuals who demonstrate repetitive
behaviors or touch certain areas of their body are giving clues to ways
that will help them self-regulate or compensate. Exploring how the behavior
and movement is helping the individual can lead to a reduction of stress
and an increased capacity to calm the nervous system. Social activities
and interpersonal skills of both children and adults with sensory integration
issues are often impaired in a variety of ways. However, recent research
has also found that as individuals become more aware of their internal
physiological responses, they can increase their ability in a variety
of ways, including expanding their empathic capacity.
While these ideas about assessment
and treatment just brush the surface, they may pique your interest in
learning more. Today, there are numerous tests and resources available—including
research, support for parents, listings for qualified Occupational Therapists
who specialize in treating SPD, and a great deal of encouragement.
www.kidfoundation.org
www.sensoryresources.com
www.sinetwork.org
www.spdnetwork.org
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Copyright: Lauren Culp and Mindy Wolff 2008
Previously published in G.A.I.N.S. Journal Quarterly Spring 08
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