The Science Behind NeuroNet
The Role of the Vestibular System in Temporal Processing
Over the past fifteen years I have come to see that the vestibular system lays the foundation for temporal processing through interhemispheric perceptual coordination of motor responses to gravity; that this coordination in turn affects auditory and visual perception; and that the motor system in a myriad of ways can impact the ability of the vestibular system to regulate temporal processing.
Imagine a child standing, eyes closed, on a rocking balance board. He will sway left and right to "keep" his balance. The amount of sway will depend on a) the patient's quality of vestibular perception; b) the patient's ability to generate motor responses to vestibular perception; and c) the difficulty of the balance task. The vestibulo-spinal reflex automatically stiffens the leg ipsilateral to the perceived direction of sway. If the sway is perceived as falling (fast sway), the arms will also be lifted in a counterbalancing reflex, and the eyes will open. At some level of graded balance difficulty, the child will appear to stand motionless, although the vestibular computations which maintain standing balance are in fact ongoing. In this sense, balance is the action of not moving.
The process of vestibular computation is ongoing, not only for balance tasks but for all purposeful movements. The newborn infant, laying face down, must exert sufficient force to overcome gravity in order to lift and turn his head. Laying face up, he must calculate not only strength but also direction of movement in order to lift his arm and reach for a toy. Although we don't think of infants as mathematicians, they are from their first experiences of gravity "calculating" or making use of interhemispheric time differences as they learn to generate purposeful movement.
Why the vestibular system?
Why does the vestibular system set the standard for temporal processing? What sets the vestibular system apart from other perceptual-motor systems? The vestibular system is unique in that perception of an invariant external stimulus (gravity) obligates a reflexive motor response. The invariant nature of the external stimulus and the obligatory nature of the motor response make the vestibular-motor system uniquely able to function as the brain's timekeeper. (Note that it is neither perception nor movement which forms the basis of temporal processing, but the obligatory neural linking of perception and movement. For this reason I have named this "The NeuroNet Program".)
All temporal processing tasks have perceptual and motor components which must be interwoven quickly enough for the tasks to remain coherent. We lose our "train of thought" when perceptual information must be re-clarified or when motor information must be reconstructed during a cognitive task. When I'm carrying on a conversation with a friend, in Spanish, I lose my train of thought if I have to stop and figure out how to construct the verb tense. My son forgets how to spell the word he's writing as he stops to figure out which way the letter /d/ is oriented. "Train of thought" implies a temporal framework for assembling pieces of information into a coherent idea (getting the "big picture"). By teasing out the relative contributions of perception, movement and timing we can develop a treatment protocol that addresses coherent temporal processing.
How do we use the vestibular system to look at perception, movement, and timing? Three principles of temporal processing guide each procedure:
- the use of gravity as the reference standard for timing;
- the use of rhythmic movement to enhance or amplify the perception of gravity; and
- the rhythmic entrainment of speech, arm movement and body movement.
Let's look at a NeuroNet procedure for translational movement. In this procedure the patient will sit and bounce rhythmically on an underinflated, knee-high ball, organize a repetitive speech task at the same time, and bounce his hands on his knees in rhythm with his talking. Gravity defines the time he has for each bounce, and thus indirectly defines the time he has for the integrated arm movement pattern and repetitive speech pattern as well. If this patient "knows" gravity, he "knows" time. He knows how much time he has to initiate, sustain and complete each repetitive movement pattern of the body, hands and mouth. He knows how to calibrate movement against gravity.
NeuroNet looks at the process of calibrating purposeful movement, including speech movement, against gravity. We measure which rhythmic movement patterns are fluent, and which are disruptive. Does loss of balance degrade flow of speech? Do arm movements degrade balance? Do speech demands degrade rhythm?
We know that conversational speech normally flows along at a rate of 4 syllables per second. Since we have eliminated the language demands of our speech task, we know that patients who cannot fluently integrate speech, arm movement and body movement at the rate of 4 syllables per second, sustained for 1 minute, will have their "train of thought" disrupted to some degree by the motor demands of balance and/or speech. This is true both for speaking and for reading. Once we have "the big picture" of perception, movement and timing factors for an individual patient, we write a program to address the specific ÒintrahemisphericÓ areas which are degrading temporal processing.
What do we mean by intrahemispheric brain areas? We mean brain areas in which a dominant hemisphere controls the behavior we are measuring. NeuroNet addresses awareness of auditory and visual detail, integration of visual and verbal information, and the ability to generate sustained fine-motor movement sequences of the fingers and mouth. Each of these areas must be addressed in a low-level multi-tasking context which includes entrained, rhythmic movement of the body, arms and mouth (speech).
For patients doing NeuroNet we expect to see significant improvements in performance within four to six weeks (scores and times are charted and graphed in some way for every procedure). Also, every patient or parent is asked to fill out a behavioral observations page of 3 comments each week. We expect to see changes in life in areas not specifically addressed by NeuroNet such as using new vocabulary, reading for pleasure, or writing more clearly and easily.
The comments of the patients and their parents who have seen major improvements make my job most gratifying. "Let me do it!" from a child who was afraid to initiate anything. "Oh, I know! I forgot to say '14'," from a child who could never self-evaluate. "He is remembering things that occurred in school and sharing with us. He never used to do this. . ." from a parent whose child initially acted out all of his feelings. And from a parent whose child was initially overwhelmed by everything in life: "he feels happy now."
Bilaterality: A Gift of Time
Human beings are bilateral people. We have two eyes, two ears, two hands and two feet. Our brains have two hemispheres, where the information from each side of our body is received, stored and called upon to direct our actions and movements. Why are we two-sided people? Research shows us that our best hearing thresholds for two ears together (binaural hearing) are always better than for either ear alone. In the same way, our best vision for one eye is never as good as our vision using two eyes (binocular vision). And although we don't consider handwriting a bilateral task, we write more quickly and accurately when the non-writing hand spontaneously stabilizes and orients the writing paper while the writing hand guides the pencil. We are bilateral people because interdependent use of the two sides of the body (and brain) makes life faster and easier.
The two sides of the body can function separately, or independently. We can see with one eye, hear with one ear, eat with one hand, and hop on one foot. But even when we use just one side of the body, we are always using both sides of the brain. In everything we do, we can do it faster or more precisely, when we use both sides of the body, or both of the eyes, or both of the ears in a coordinated way. This coordination, or interdependence, is orchestrated by the brain. The savings in time may seem small, but think of it this way: if we were to gain just one second of free time for every minute of our day, we would have an extra 24 minutes each day to appreciate life. Five minutes can be a lot of time if you're running late. Five seconds can be a lot of time if you're trying to follow complicated directions in class or take notes.
Temporal Processing and Basic Skills
What happens if, instead of gaining one second each minute, we lose one, or even two, or more seconds. Marginal clumsiness, in sight, hearing, or movement, is costly. The basic skills of daily living (motor skills, talking, reading, writing and counting) are all organized within explicit or implicit time limits. Verb tenses are our linguistic labels for time. Words such as "when", "while", "because" and "so that" link events that have defined time relationships. Knowing these time relationships makes life more predictable and secure. Children whose internal sense of time is not constant have difficulty being on time, using the language of time, and understanding the time relationships of cause and effect.
Apart from the explicit social conventions of time management, there are implicit time limits imposed on basic skills. Conversation moves from one turn to the next with a two-second pause between turns. The child who easily carries on a conversation with friends and family develops higher and higher levels of language and social skills, and becomes a confident communicator. Self-confidence develops through the ability to predict success (we talk to people because we think they will understand what we say), and then to make that prediction come true (the satisfaction of being understood).
Development of Simple Behaviors
Human beings all over the world have many simple behaviors in common. We all walk and run and jump. We all talk and sing and dance. We "develop" (as opposed to "learn") these simple behaviors by living in a world where we are exposed to them. From earliest infancy, humans have an innate tendency to imitate the patterns of sound and movement they experience again and again every day.
In their daily lives, children are given the opportunity and encouragement they need to imitate simple perceptual and motor skills. All children develop these perceptual and motor skills within a range of levels of ability and at varying rates of progress. Simple skills such as walking, jumping, running and talking are indicators of neural organization. These basic skills create the foundation for the complex brain functions which in turn enable us to develop useful skills such as reading and writing.
In the "simple" activities of daily living we are all required to manage many kinds of attention, or neural organization, at the same time. For example, while carrying on a conversation we are integrating eye contact (visual processing), language comprehension (auditory processing), talking (fine motor movements of mouth), and posture (vestibular-motor processing), all while we plan our thoughts and choose our words.
We call the process of performing many simple tasks at one time "low-level multitasking". NeuroNet is designed to take a measured look at a patient's ability to manage the simple behaviors of balance, hand movement and speech all at the same time.
Why do we evaluate multi-tasking?
The distribution of cognitive resources is essential to the ability to pay attention. If too much attention (cognitive resources) must be devoted to perceptual/motor tasks (such as the body movements of balance, the mouth movements of speaking; the eye movements of reading; the hand movements of writing), then higher-order tasks requiring significant cognitive resources (language, reading and writing) will be compromised.
This compromise in cognitive performance is not due to lack of intellectual ability but to inadequate cognitive resources for the competing demands of perceptual/motor and cognitive tasks. Attention which must be allocated to basic perceptual/motor tasks is not available for higher-order cognitive skills.
We use NeuroNet procedures to automate perceptual/motor tasks (movement patterns of body center, mouth, head, arm and hand) in the time framework given by gravity. All movements rhythmically calibrated against gravity will in turn be calibrated against each other. The purpose of the NeuroNet procedures is to automate basic concurrent perceptual/motor tasks in order to maximize the cognitive resources available for higher-order information processing (visual-motor problem-solving, communication and language skills, reading comprehension, and written language).
We evaluate vestibular, auditory and visual processing all in the context of low-level multi-tasking for two reasons. Most importantly, this is how we function in daily life. Behaviors which cannot be performed in a multi-tasking context are not useful life skills. Secondly, we know that many simple behaviors can be performed at either a conscious (slow) or an automatic (fast) level. Only by using multi-tasking procedures performed in measured amounts of time can we assess whether or not a behavior is fast enough, or automatic enough, to be a useful skill.
How fast is fast enough?
Our sense of timing is a part of every move we make. What happens if you walk too slowly? You lose your balance. And what happens if you talk too slowly? You lose your train of thought. Unwritten standards of timing underlie all simple behaviors. Measures of timing show us when simple behaviors, such as walking and talking, are fast enough, or automatic enough, to support more complex behaviors, such as reading and writing. A child who struggles to remember how to form written letters will forget how to spell words. A child who struggles to remember how to spell words will forget the ideas they are trying to express in a sentence. We need to know if simple perceptual and motor behaviors are "fast enough" for us to learn and remember new skills.
Why is gravity our obligatory timing standard?
Calibration of body movement against a universal constant (the force of gravity) gives a timing framework into which all purposeful motor behaviors must be integrated for efficient movement patterns.
Our sense of timing arises from our experiences with gravity. The vestibular system is the perceptual system that enables us to calculate the effect of gravity on movement. The human brain is designed to calibrate movement against the force of gravity. We are designed to "know", in an intuitive way, how the force of gravity affects our movements. We calculate, or calibrate, how much strength it takes to lift one leg, and at what time the foot must go down to be ready for the next step in a movement pattern as "simple" as walking. Through movement, we learn to calculate how gravity affects our body. Through calculation, or calibration, of movement against gravity, we develop our sense of timing.
The vestibular system mediates this calibration process through a developmental sequence of primitive reflexes, postural reflexes, and purposeful movements. As we learn to predict the effect of gravity on all of our movements, we develop a sense of timing. We become able to predict how much time we will have to take the next step, say the next word, or reach out to touch an object. "Planning ahead" is the essential neurological process which underlies the ability to automate low-level perceptual and motor behaviors.
The NeuroNet Program uses low-level multitasking in the three bilateral sensory-motor systems (vestibular, auditory, visual) to entrain temporal processing among these three systems. By linking auditory-motor (speech) and visual-motor (hand-eye) coordination skills to vestibular skills, we define the amount of time available for brief hand and speech movements. Through the vestibular system, we gain control of temporal processing in the auditory and visual systems. The NeuroNet Program is designed to automate the basic perceptual-motor skills of balance, hand movements and speech which are the essential components of many daily behaviors.
Explicit vs. Procedural Memory
Simple perceptual-motor behaviors may be remembered in different ways by the brain. As we observe a behavior such as reciting the alphabet, we do not know what kind of memory is used to generate this behavior. Overlearned behaviors which become habit and are generated with little conscious attention are managed by procedural memory. Behaviors which are new or which require conscious attention are managed by explicit memory. Efficient use of limited cognitive resources means that we must manage as many behaviors as possible at the level of procedural memory.
NeuroNet is designed to assess the kinds of memory being used for basic perceptual-motor skills, and to facilitate the transfer of simple perceptual-motor skills from explicit memory to procedural memory. When basic skills (balance, hand movements of talking and writing, mouth movement sequences of speech) are managed by procedural memory, cognitive resources may be then be used for the ongoing global communication tasks of language and reading comprehension, and spoken and written language production.
How is NeuroNet different?
The significant concepts which differentiate the NeuroNet program from other sensory and motor therapies are:
- the use of gravity as the reference standard for timing, or temporal processing;
- the use of rhythm to enhance or amplify the perception of gravity;
- the sustained, rhythmic integration of movement (coincident onset of movement) in:
- calibration of purposeful movement against gravity; and
- rhythmic multitasking of perception, movement and cognition