Here is an example to illustrate modulation: Imagine turning on the gas jet to warm the tea kettle. At first, you turn the dial a bit too far, too fast, and the gas leaps high. If you keep the dial there, the water will quickly come to a boil. But if you twist the dial back to inhibit the gas, the gas will calm down and heat the water at a moderate pace. You have modulated the amount and intensity of fire.
When excitation and inhibition are balanced, we can make smooth transitions from one state to another. Thus, we can switch gears from inattention to attention, from sulks to smiles, from drowsiness to alertness, and from relaxation to readiness for action. Modulation determines how efficiently we self-regulate, in every aspect of our lives.
Sensory Discrimination
Another aspect of sensory processing is discrimination, the ability to tell the difference among and between sensory stimuli. Discrimination has to do with the temporal and spatial characteristics of sensations—that is, with characteristics of timing and space.
Say you are on the beach, playing Frisbee with your child. The Frisbee flies through the air. With good sensory discrimination, you perceive it coming toward you, judge how fast it is approaching and where it is in space, and run at the right pace to the right place to catch it. “Aha!” the brain says as it processes all that Frisbee information. “I know what this means and just how to respond!”
Sensory discrimination allows us to perceive:
• Qualities of sensations—How fast am I moving? Where am I? Is my voice loud? Are my shoes tight? Is this bucket heavy? Is that snow cold?
• Similarities of sensations—Have I heard that song before? Does “four” rhyme with “door”…or with “five”? Is my right arm stretched as high as my left arm? Does this rabbit feel like my cat?
• Differences among sensations—Is this sound I hear “cot” or “cog”? Is that symbol a Stop sign or a Yield sign? Which train is moving—the one I’m on or the one on the next track?
Sensory discrimination develops with neurological maturation. As a child matures, he responds less self-protectively to every sensation and becomes more discriminatory about what is happening in his body and the environment. He learns to use sensations for organized behavior. For instance, when Granny arrives at the door, the child runs for a hug because integrated sensations about what he has seen, whom he has touched, and how he has moved through space teach him how to respond.
Please note: Discrimination should take precedence over defensiveness in everyday situations. Of course, at any age, a person can always revert to defensiveness when a true threat occurs, for this capability diminishes but does not disappear.
HOW SENSORY DISCRIMINATION TAKES PRECEDENCE OVER SENSORY DEFENSIVENESS AS CHILDREN MATURE
Child’s Age Growing Importance of Discrimination
Infant: Defensiveness is weightier.
Toddler: Defensiveness and discrimination level off.
Kindergartner: Discrimination is weightier.
The chart on page 60 gives a general picture of how this shift occurs as the child develops.
Sensory-Based Motor Skills
In a nanosecond, the CNS receives, detects, integrates, modulates, and discriminates incoming sensory messages. The end result of sensory processing is when the brain sends outgoing messages that prepare the person to do something. Immediately, the brain says, “OK, let’s move!” (Or, “Let’s act! Let’s not act! Let’s think! Let’s pay attention! Let’s talk, cry, or giggle!”)
For instance, when motor output goes to the arms, legs, eyes, and other body parts, it prepares the child to move in a satisfying way that encourages her to do more and to do it better. Motor output involves postural responses and praxis.
POSTURAL RESPONSES
Efficient sensory processing is necessary for normal movement. Equipped with the sensory information he needs, the child has good postural responses and bilateral coordination.
Postural responses extend the child’s trunk, neck, and head upward, against the pull of gravity. His equilibrium and bilateral coordination allow him to experiment with different movements and positions. The child can get into and stay in a stable position. He can get into an unstable position, too, such as leaning over to retrieve a dropped pencil, and then regain his balance.
With firm muscle tone, he bends and straightens his muscles to stretch and reach. He grasps, turns, and releases objects such as spoons and doorknobs. He gets on a swing and, in Dr. Ayres’ words, can “hold on and stay put.” He enjoys different kinds of weight-bearing movement, such as crawling and doing push-ups. Changing positions smoothly, he shifts his weight from foot to foot, or rotates body parts, whipping his arms around his torso like a flag on a pole.
The child maintains his balance and upright position when standing or sitting. He uses both sides of the body together to catch a ball, watch a bird fly, and jump with both feet. He uses one side alone to kick a ball, and, by the age of four or five, writes with a preferred hand.
Good postural responses contribute to the child’s confidence that he can control his body and master new challenges.
PRAXIS
How do you learn to run, skip, type, flip pancakes, or use a digital camera? How do you get to Carnegie Hall?
Praxis, praxis, praxis!
Praxis (Greek for “doing, action, practice”) is based partly on efficient, unconscious sensory processing and partly on conscious thought. It is a broad term denoting coordinated and voluntary action. (The term “motor planning” is often used as a synonym for praxis.) Praxis is the ability:
1) To ideate, or conceptualize, an unfamiliar and complicated action involving several steps,
2) To organize one’s body to carry out the motor plan, and
3) To execute, or carry out, the plan, or at least make some progress.
Praxis permits us to do what we need and want to do as we go about our occupations of daily living. Thanks to praxis, we can pump on a swing and pump gas, write in cursive and line up a column of numbers, grind pepper and punch the right elevator button, suck poppy seeds from our teeth and whistle “Dixie.”
The child is not born with praxis. Praxis is a learned skill. The child develops it over time as she touches and explores objects and learns to move her body in different ways. Each time she rehearses ordinary actions such as handing out cupcakes, zipping her jacket, and organizing her backpack, her motor planning skills improve.
Mastering one motor skill leads to trying another that is more challenging. The more the child does, the more she can do. For instance, after gaining confidence on a jungle gym, a child may use her skills to climb a tree or hang upside down from a monkey bar. This is an example of adaptive behavior.
The Process of Sensory Input, Organization, Motor Output and Continual Feedback
Adapted with permission from Anita C. Bundy and Jane Koomar: “Orchestrating intervention: The art of practice,” in Bundy, A.C., Lane, S.J., and Murray, E.A.: Sensory Integration: Theory and Practice, 2nd ed. (2002). Philadelphia: F.A. Davis, p. 256.
Sensory Processing Working As It Should
In a nutshell, sensory processing involves input, organization, and output. Sensory input is the neurological process of receiving messages from receptors inside and on the surface of the body. In the next step, the brain organizes the sensations. In the motor output part of the process, the brain sends out instructions to the body so the person can do what she wants to do—run, play, climb, talk, eat, sleep, and so forth. As the person engages in all these human activities, the movement of the body and the doing of the activity lead to more sensory input through the sensory receptors and more feedback to the brain. The illustration on page 63 shows this cycle.
Here is how sensory processing works as it should: Suppose you are sitting on the couch, leafing through the newspaper. You pay no attention to the upholstery touching your skin, or the car passing by outside, or the position of your hands. These sensory messages are irrelevant, and you don’t need to respond to them
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Then your child plops down beside you and says, “I love you.” Simultaneously, your senses of sight, hearing, touch, movement, and body position (and maybe smell, too) are stimulated. Sensory receptors throughout your peripheral nervous system take in all this information and sweep it into your central nervous system. The information zooms to your brain.
Now, these sensory messages are relevant. Swiftly, your brain organizes them and then sends messages back out so you can produce a sensory-motor response.
You respond with language: “I love you, too.”
You respond with emotion: a gush of affection.
And, because you know where you are and where your child is, you know how much time it will take to get to her. Anticipating how much force to use for a “feel good” hug, you respond with movement. You drop the newspaper, lean over, open your arms, and embrace your child.
No one part of the central nervous system works alone. Messages must go back and forth from one part to another. When sensory messages come in and motor messages go out in a synchronized way, we can do what we need to do.
THREE EXAMPLES OF INPUT, ORGANIZATION, AND OUTPUT USED IN SMOOTH SENSORY-MOTOR RESPONSES
The Blaring Horn
SENSORY INPUT: Walking to work, you hum along to a song playing through your earphones. At an intersection, you look both ways, decide it’s safe to cross, and step off the curb. Then you hear a blaring horn. Your auditory (hearing) sense receives the stimulus of the sound and sends the message to your brain.
NEUROLOGICAL ORGANIZATION: Suddenly, you stop hearing the music. Your brain has a more urgent task: to filter out all irrelevant sounds, analyze the new message, interpret the sound as a danger signal, and organize the information for use.
MOTOR OUTPUT: Your brain tells you how to react with an appropriate motor response. You do what you need to do and jump back.
The Sour Plum
SENSORY INPUT: You see a plum that looks juicy, ripe and sweet. You bite into it and discover that your expectation was wrong; it’s sour. Your gustatory (taste) sense sends the message to your brain.
NEUROLOGICAL ORGANIZATION: Your brain interprets “sour” as harmful and organizes the sensory message for use.
MOTOR OUTPUT: Your brain tells the muscles in your mouth how to respond. You spit out the morsel and tell yourself to check more carefully the next time.
The Tilting Chair
SENSORY INPUT: Seaside, you lower yourself into a folding aluminum chair. The chair’s back legs plunge into the sand. Unexpectedly, you tip backwards.
NEUROLOGICAL ORGANIZATION: Your brain analyzes this loss of equilibrium.
MOTOR OUTPUT: Your brain instructs you to protect yourself. Your core muscles contract, your head cranes forward and your hands grab the armrests. You regain your balance before tumbling backwards and upside down into the sand.
The more efficient our brain is at processing sensory input, the more effective our behavioral output will be. The more effective our output, the more feedback we receive to help us take in new sensory information and continue life-sustaining, never-ending sensory processing.
THE TYPICAL DEVELOPMENT OF SENSORY PROCESSING IN INFANTS AND CHILDREN
Becoming functional is a developmental process. It evolves as the maturing child builds his sense of self.
Dr. Ayres used a diagram to show four levels of sensory development. Her concept could be compared to a child’s block construction. At first, the little child pushes blocks around on one level. Eventually, he figures out how to add a second level to the first. Then he adds a third level, and a fourth.
Sensory processing builds the same way. Each level rests on the building blocks laid down before. Just as the top level of the child’s block building needs support, so his readiness for complex skills rests on the foundation of the tactile, vestibular, and proprioceptive senses. (See Appendix B for a discussion of the four levels.)
A Variation of Dr. Ayres’s “Four Levels of Sensory Integration”
By the time a child is ready for preschool, the blocks for complex skill development should be in place. What are these blocks?
• Ability to modulate touch sensations through the skin, especially unexpected, light touch, and to discriminate among the physical properties of objects by touching them (tactile sense),
• Ability to adjust one’s body to changes in gravity, and to feel comfortable moving through space (vestibular sense),
• Ability to be aware of one’s body parts (proprioceptive sense),
• Ability to use the two sides of the body in a cooperative manner (bilateral coordination), and
• Ability to interact successfully with the physical environment; to plan, organize, and carry out a sequence of unfamiliar actions; to do what one needs and wants to do (praxis).
Every child has an appetite for sensory nourishment. Inner drive, or self-motivation, urges him to participate actively in experiences that promote sensory processing. In daily life, he explores the environment, tries new activities, and strives to meet increasingly complex challenges. Mastering each new challenge makes him feel successful, and success gives him the confidence to forge ahead.
SO, WHAT IS SENSORY PROCESSING DISORDER?
Sensory Processing Disorder is difficulty in the way the brain takes in, organizes and uses sensory information, causing a person to have problems interacting effectively in the everyday environment. Sensory stimulation may cause difficulty in one’s movement, emotions, attention, or adaptive responses. SPD is an umbrella term covering several distinct disorders that affect how the child uses his senses.
Having SPD does not imply brain damage or disease, but rather what Dr. Ayres called “indigestion of the brain,” or a “traffic jam in the brain.” Here is what may happen:
• The child’s CNS may not receive or detect sensory information.
• The brain may not integrate, modulate, organize, and discriminate sensory messages efficiently.
• The disorganized brain may send out inaccurate messages to direct the child’s actions. Deprived of the accurate feedback he needs to behave in a purposeful way, he may have problems in looking and listening, paying attention, interacting with people and objects, processing new information, remembering, and learning.
Pinpointing a person’s specific type of SPD matters greatly in order to decide upon the most appropriate treatment. (See Chapter Eight). The categories of Sensory Modulation Disorder, Sensory Discrimination Disorder, and Sensory-Based Motor Disorder—mentioned in Chapter One—are explained more fully here.
Sensory Modulation Disorder
A common problem among children with SPD is Sensory Modulation Disorder (SMD). This is a problem of timing in the CNS. Inhibition must be timed just right to balance excitation, so that simultaneous sensory messages can be synchronized.
A child with quick or intense inhibition has a low threshold for sensations, whether they are meaningful or meaningless, positive or negative. He’s the tea kettle with the gas turned up too high. Sensations “pour on the heat,” activating all his receptors. He responds to them all, roiling and boiling, bubbling over. He needs help to simmer down.
A child with slow inhibition has a high threshold for sensations. She’s the tea kettle with the gas turned too low; she is not receiving enough heat to get activated. She needs help to light her fire.
What happens when a child’s nervous system has a problem with modulation? The child may be overresponsive, underresponsive, sensory craving, or have a combination, with fluctuating responsivity. All of these problems interfere with the child’s interactions at home, at school, and in the community. He needs guidance to help him “come to the table,” be part of the family or classroom team, and engage in active, meaningful play.
SENSORY OVERRESPONSIVITY: THE SENSORY AVOIDER—“OH, NO!”
The most frequently seen type of a sensory modulation problem is overresponsivity to sensations coming from one or several systems. (Synonymous terms are hypersensiti
vity, hyperresponsiveness, hyperreactivity, oversensitivity and sensory defensiveness.) Overresponsivity to touch stimuli and sounds is common and often referred to as “tactile defensiveness” and “auditory defensiveness.” “Sensory defensiveness” is the term used when all the senses are affected.
The overresponsive child’s brain cannot inhibit sensations efficiently. He may be quite distractible because he is paying attention to all stimuli, even if the stimuli are not useful. Overaroused and unable to screen the irrelevant from the relevant, he seeks to defend himself from most sensations. He may respond as if they were irritating, annoying, or even threatening.
Most people alert to a novel sensory experience—say to a light touch or a lump in the mashed potatoes—and then shrug it off, but this child cannot let it go. Instead of responding with a typical, “Uh, oh, what’s that?” he may respond with, “Oh, no! Don’t do this to me!” Most people respond to a scary situation—say, a bumblebee or angry shouts—with a fight, flight, freeze, or fright response, eventually calming down, but this sensory avoider goes to extremes.
How does his fight, flight, freeze, or fright response play out? If “fight” is his modus operandi, he responds with vigorous resistance or hostility. He may be negative and defiant, lashing out.
If “flight” is his manner, he reacts with an aversive response. An aversive response is a feeling of revulsion and repugnance toward a sensation, accompanied by an intense desire to avoid or turn away from it. The child may actively withdraw, fleeing from sensations by running away, jumping back, hiding under the table, climbing on furniture or trying to claw his way out, desperate to get away from perceived threats.
Or, he may “flee” by withdrawing passively, simply avoiding the people and objects that distress him. He never gets close to them, or he walks away. Often, adults think he avoids mud pies and merry-go-rounds because “those just aren’t his thing.” In fact, he may yearn to participate in the activities his classmates enjoy, but just can’t.
The Out-of-Sync Child Page 8