JOURNAL OF CHILD AND ADOLESCENT PSYCHOPHARMACOLOGY
Volume 2, Number 1, 1992 Mary Ann Liebert, Inc., Publishers
CERTAIN SENSORY PROCESSING problems may be explained by cerebellar abnormalities. In addition to the familiar roles of the cerebellum in motor coordination and balance, there are suggestions that the cerebellum may also have functions in sensory processing. Early studies found that stimulation of the cerebellar vermis caused a cat to become hypersensitive to touch and to sound (Chambers 1947). More recent work in rats also suggests that the cerebellum acts as a modulator of sensory input for various sensory modalities, effectively functioning as a type of volume control; lobules V, Vl, and VII of the vermis appear to be the most crucial sites (Crisping and Bullock 1984). People with autism have many sensory processing deficits, including problems in modulating sensory input (Ornitz 1985). Most research on sensory processing problems in autistic individuals has studied the auditory and visual modalities. It may be hypothesized that some of the sensory processing problems in autistic disorder might be related to abnormalities of the cerebellum.
Courchesne et al. (1988) found that a majority (14/18) of high-functioning adults with autistic disorder had cerebellar abnormalities. Brain autopsy research has also revealed cerebellar abnormalities in autism, especially in lobules V, Vl, and Vll of the vermis (Bauman and Kemper 1985, Ritvo et al. 1986).
When I was age 3, I had standard autistic symptoms such as intolerance to being touched, inability to speak, tantrums, and stereotypic behavior. I would stiffen and pull away when people touched me, and I was oversensitive to both touch and sound (Grandin 1989a, Grandin and Scarino 1986) Magnetic resonance image (MRI) scans have revealed that my cerebellum is undersized, and I have a slight balance problem.
I will describe here a deep touch pressure device ("squeeze machine") that I developed to help me overcome problems of oversensitivity to touch, and that allays my nervousness. Reactions of other people to the squeeze machine, including children with autistic disorder and attention-deficit hyperactivity disorder (ADHD) are also reported.
Finally, the animal literature on deep touch pressure will be surveyed, revealing that similar calming reactions may be generally observed in response to deep touch pressure in higher animals. However, in view of the possibility that cerebellar abnormalities may cause hypersensitivity to touch, the therapeutic response of children with autism to correctly applied deep touch pressure might be partially explained by a cerebellar mechanism.
CLINICAL EFFECTS OF DEEP TOUCH PRESSURE
Deep touch pressure is the type of surface pressure that is exerted in most types of firm touching, holding, stroking, petting of animals, or swaddling. In contrast, light touch pressure is a more superficial stimulation of the skin, such as tickling, ver y light touch, or moving hairs on the skin. In animals, the tickle of a fly landing on the skin may cause a cow to kick, but the firm touch of the farmer's hands quiets her. Occupational therapists have observed that a very light touch alerts the nervous system, but deep pressure is relaxing and calming.
Deep pressure touch has been found to have beneficial effects in a variety of clinical settings (Barnard and Brazelton 1990, Gunzenhauser 1990). In anecdotal reports, deep touch pressure has been described to produce a calming effect in children with psychiatric disorders. Deep pressure stimulation, such as rolling up in a gym mat, has been used to calm children with autistic disorder and ADHD (Ayres 1979, King 1989). Lorna King (personal communication, 1990) reports that children with sleeping problems a ppear to sleep better inside of a mummy sleeping bag, which adapts to fit the body snuggly. It also has been used to reduce tactile defensiveness in children who cannot tolerate being touched. McClure and Holtz-Yotz (1991) found that deep pressure applied by foam-padded splints on the arms reduced self-injurious behavior and self-stimulation in an autistic child.
Research on autistic children indicates that they prefer proximal sensory stimulation such as touching, tasting, and smelling to distal sensory stimulation of hearing and seeing (Kootz et al. 1981). Autistic children will often seek out deep pressure sens ations. At various lecture meetings of parents of autistic individuals, parents have reported to me various types of pressure-seeking behavior of their offspring, such as wrapping arms and legs in elastic bandages, sleeping under many blankets even during warm weather, and getting under mattresses. In my case, l used to crawl under sofa cushions and have my sister sit on them. A high functioning autistic woman stated, "I need heavy blankets on me to sleep well, or else my muscles won't calm down."
Deep touch stimulation is beneficial to normal babies (Barnard and Brazelton 1990, Gunzenhauser 1990). Institutionalized babies who received supplemental tactile stimulation, mainly deep touch pressure, developed more normally (Provence and Lipton 1962). Premature babies who receive stroking and tightly bound swaddling also are reported to show definite benefits (Anderson 1986, Field et al. 1986, Lieb et al. 1980).
The strong need for deep touch stimulation is suggested in Harlow and Zimmerman's classic experiment (1959): baby monkeys would cling to and press against a soft cloth mother surrogate which provided contact comfort, over a wire surrogate that provided milk.
Takagi and Kobayasi (1955) found that deep pressure applied bilaterally to a personta body results in a decrease in pulse rate, metabolic rate, and muscle tone. This finding, however, has not been replicated.
FIG. 1. Rear view of the squeeze machine showing the position of the user between the padded side boards. Krauss (1987) designed an air mattress apparatus which applied pressure to large areas of the body. The apparatus consisted of two air mattresses surrounded by a canvas wrap connected to a pulley. A person laying between the two mattresses could control pressure applied by pulling on a rope, which tightened the canvas wrap. In this study, college students reported mild subjective reductions in anxiety and were found to have mildly increased heart rate, but neither finding reached statistical significance. However, this rope-operated apparatus applied considerably less pressure than the "squeeze machine" (Grandin 1984, Grandin and Scariano 1986).
THE SQUEEZE MACHINE
The squeeze machine device developed by the author consists of two padded side boards which are hinged at the bottom to form a V shape. The user steps into the machine and lies down on the inside in the Vshaped crevicelike space. The inside surfaces of the device are completely lined with thick foam rubber. Deep touch pressure stimulation is applied along both sides of the person's body, with lateral pressure pushing inward onto the body (Fig. 1). The V-shaped space supports the body fully from head to toe, so that the users can completely relax. The contoured padding provides an even pressure across the entire lateral aspects of the body without generating specific pressure points. The foam-padded head rest and padded neck opening are covered with soft fake fur. When the neck opening closes around the neck, it enhances the feeling of being surrounded and contained by the embrace of the deep touch pressure squeeze.
The user has complete control over the amount of pressure applied (Fig. 2). A lever-operated pneumatic valve, which is connected to an air cylinder that pulls the side boards together, allows the user to self-regulate the amount of pressure applied. For a dults, the air pressure on the 5 cm diameter air cylinder is set at 60 psi, which allows up to 43 kg (95 Ibs.) of pressure to be exerted on each rope attached to the sides. For children under age 8-9 years, the pressure is set at 30 to 40 psi.
The user can enter and leave the machine at will, which confers a more complete sense of self-control in the context of the machine. The squeeze machine and procedures for its use are more fully described elsewhere (Grandin 1984, Grandin and Scariano 1986 ).
The advantage of the squeeze machine over other forms of deep pressure stimulation, such as rolling in mats, is that the machine can apply greater amounts of pressure over larger areas of the body. The air cylinder power applies constant pressure, even when the user shifts position.
FIG. 2. Front view of squeeze machine showing the user operating the control lever which activates the squeeze pressure.
THE AUTHOR'S EXPERIENCE WITH SQUEEZE MACHINE
As a child, I craved to feel the comfort of being held, but I would pull away when people hugged me. When hugged, an overwhelming tidal wave of sensation flowed through me. At times, I preferred such intense stimulation to the point of pain, rather than a ccept ordinary hugs. On the Ayres Checklist for Tactile Defensiveness ( 1979), I had 9 out of 15 symptoms by age 10 years. Whenever anyone touched me, I stiffened, flinched, and pulled away. This approach-avoidance characteristic endured for years during my childhood.
At puberty, anxiety and nervousness made me feel as though I was constantly in a state of "stage fright." While the nature of this anxiety was not diagnosed at the time, they have been retrospectively diagnosed as panic attacks, and would fulfill the DSM-III-R criteria.
At age 18, I constructed the squeeze machine to help calm down the anxiety and panic attacks. Using the machine for 15 minutes would reduce my anxiety for up to 45-60 minutes (Grandin and Scariano 1986). The relaxing effect was maximized if the machine was used twice a day.
Gradually, my tolerance of being held by the squeeze machine grew. Knowing that I could initiate the pressure, and stop it if the stimulation became too intense, helped me to reduce the oversensitivity of my "nervous system." A once overwhelming stimulus was now a pleasurable experience.
Using the machine enabled me to learn to tolerate being touched by another person. By age 25, I was able to relax in the machine without pulling away from it. It also made me feel less aggressive and less tense. Soon I noted a change in our cat's reaction to me. The cat, who used to run away from me now would stay with me, because I had learned to caress him with a gentler touch. I had to be comforted myself before I could give comfort to the cat.
As my "nervous system" calmed down, I required less squeeze pressure to produce a comforting feeling. Gradually, I could reduce the pressure regulator setting from 80 to 60 psi.
From my experiences, I learned that if pressure from the squeeze machine is applied at a steady pressure, habituation would occur and discomfort would begin within 10 to 15 minutes. Instead, if the pressure is increased and decreased slowly, the soothing effect could be maintained for up to one and a half hours. Very slow movement of the squeeze sides was most soothing. Sudden jerky movements caused me to jump and become aroused. On most occasions, a 5-15 minute period in the machine was sufficient to get a good response.
EFFECTS OF THE SQUEEZE MACHINE ON NORMAL ADULTS
Deep pressure applied to a wide area of the body, administered by the squeeze machine, has a relaxing effect on normal adults. In the present study, college students were found to feel relaxed after use of the squeeze machine. College students (18-25 year s old) were not informed of the purpose of the squeeze machine, and simply were told that it was part of a sensory perception experiment. The operation of the machine was described to each student, and the author got into the machine to demonstrate its use. Each student was tested individually to prevent students from influencing each other's response. After 5-10 minutes, 45% ( 18/40) of the subjects employed words such as "relaxing" or "sleep" to describe their reactions. Four students ( 10%) used the wo rds "floating," "weightless," or "flight" to describe the sensation. Relaxation was physically evident in some subjects. After being in the machine for a few minutes, the squeeze sides could be pulled closer together without increasing the pressure setting.
Two people (5%) had a claustrophobic reaction to the machine and could not complete the experiment. For 40% of subjects, the machine appeared to have no relaxing effect.
Of the entire group, 25 students were asked, "If you could buy this machine in a store, what could you use it for?" "Relaxer" or "tension reliever" was the response of 17 students. One student, who did not feel relaxation after using the machine, suggested that it could be used as an isometric exerciser.
In a subgroup of 18 students, the squeeze machine was operated in three arbitrarily selected ways: (1) stationary pressure, (2) fast rhythmic pulsation of 50 cycles per minute, and (3) slow rhythmic pulsation of 15 cycles per minute. At the stationary setting, the tension on the ropes to the squeeze sides was 40 kg, a setting that most adults find tight but comfortable. During the two pulsation modes, the pressure was reduced until the top of the squeeze sides moved I cm on each side. After 5 minutes in the machine, each student was instructed to rate their state of relaxation on a scale from I ("almost asleep") to 10 ("very excited").
The data in Table I indicate that the stationary mode and the slow pulsation mode were more relaxing than the fast mode.
I also have conducted some preliminary experiments that suggest that the squeeze machine may have an effect on auditory threshold (Grandin 1970). This possibility was investigated in view of the findings that cerebellar mechanisms might modify sensory inputs involving sound as well as touch.
USE OF THE SQUEEZE MACHINE IN TREATMENT OF CHILDREN
For the last 10 years, several occupational therapists and psychologists have used this squeeze machine with autistic and hyperactive children. Six machines currently are being used for sensory integrative therapy, and beneficial effects are being described anecdotally. Lorna King, Director of the Center for Neurodevelopmental Studies in Phoenix (Arizona) reports that the squeeze machine is useful for children with autistic disorder, attention-deficit hyperactivity disorder, or learning disabilities. Margaret Creedon at the Michael Reese Hospital in Chicago reports that children with pervasive developmental disorder (PDD) and children with Tourette's disorder like to use the machine and that it calms them; it is claimed to help to inhibit tantrums and reduce stereotypies. However, there is a severe lack of formal research data pertaining to the clinical treatment of children.
||Stationary pressure||Slow pulsation||Fast pulsation|
|Rating (mean)||4.1 + 1.3||4.3 + 2.2||7.3 + 1.6*|
|Range||2 - 7||2 - 9||5 - 10|
|Number of subjects||18||18||18|
|Number of subjects with rating below 6||16||13||3|
|Percentage of subjects with rating below 6||89%||72%||17%|
The squeeze machine was employed by 18 subjects using three arbitrarily selected modes: stationary pressure, slow rhythmic pulsation of 15 cycles per minute, and fast rhythmic pulsation of 50 cycles per minute. Each subject experienced all three settings, for 3 minutes in each mode, in random order during a 15 minute session. After experiencing each mode, subjects rated their state of relaxation on a scale of 1 (almost asleep) to 10 (very excited). An analysis of variance on the entire sampling resulted in an F value - 19.33 (p < 0.0001).
*To assess differences among the three modes, a Duncan's multiple range test was applied, using .05. A statistically significant difference was noted for relaxation ratings for Fast Pulsation, compared with ratings for either Slow Pulsation or Stationary Pressure; these latter two modes were not different from one another.
One study (Imamura et al. 1990) examined behavioral effects of the squeeze machine on 9 children, aged 3-7 years, with autistic disorder or PDD. Hyperactivity was found reduced in 4 subjects, and the machine had no effect on 5 children. One child first began to hug the therapist after using the machine. The parents of a 7-year-old, high-functioning autistic boy reported that they could tell the days on which he had used the machine by observing his calmness. When the squeeze machine was not available to him, this boy learned to roll up in a quilt and then roll on the floor for 15 to 45 minutes every day to obtain adequate pressure stimulation.
Sessions with the machine were relatively unstructured, and usage usually was less than two minutes daily. There appeared to be a relationship between longer duration of squeeze machine usage and beneficial effects. Some children in their studies appear to have failed to use the squeeze machine long enough to have an effect. Imamura et al. (1990) concluded that a more structured approach, designed to encourage greater use of the machine, probably would result in increased beneficial effects.
The author initially conceived of the idea for the squeeze machine from her observations in animal science. Cattle being held in a squeeze chute, while waiting in line for veterinary attention, often appeared somewhat agitated during the waiting; some of the animals, however, seemed to relax once pressure was applied to large areas of their bodies.
Deep pressure stimulation of diverse forms have been reported to have calming effects in a variety of animals. For example, stroking and scratching the flank of a pig has long been known to induce inactivity (Marcuse and Moore 1944), and pigs spontaneously seek body contact against a solid surface (Hartsock 1979). Pressure applied to both sides of a pig in a padded V-shaped trough will induce sleep and relaxation (Grandin et al. 1989). In rabbits, gentle but firm pinching of the skin with padded clips will lead initially to arousal, followed by relaxed muscle tone, drowsiness, and deactivation of electroencephalogram (EEG) patterns (Kumazawa 1963). Likewise, a "squeeze machine" for chicks, constructed from hollowed-out foam rubber blocks, reduces separation distress (Jack Panksepp, Bowling Green University, personal communication). In cats, rubbing and gentle pinching of a paw will decrease tonic activity in the dorsal column nuclei and somatosensory cortex (Melzack et al. 1969).
In infant animals (and brain-damaged humans), pressure exerted on the face by an elastic bandage wrapped around the head will override the vestibular system and cause the head to fall back (Teitlebaum 1977). Wrapping a bandage around the torso of a cat causes the hind quarters to topple (Teitlebaum 1982).
The reactions of cattle to being restrained in a squeeze-restraining device are very similar to people in the squeeze machine. Strong pressure initially causes cattle to relax, but will lead to struggling and discomfort when the animal habituates. Habituation occurs more quickly in cattle being held against unpadded metal surfaces. Pressure must be decreased if the animal is held in a chute for more than two minutes.
Recently I operated a cattle-restraining chute that was fitted with hydraulic controls; these provide more precise control over the amount of pressure and the speed of movement of the apparatus. Any sudden jerky movement caused animals to jump and become agitated. If pressure was applied slowly, many animals would remain passive and not resist. Squeezing in a smooth steady motion, required less pressure to keep the animal still. This chute was equipped also with a head restraint yoke, which would rise up under the animal's chin after the body was restrained. Some cattle would fight the chin yoke by keeping their heads in a crooked position, which made it impossible to restrain them fully. Sudden bumping often caused the animal to resist. By gently pressing the yoke against them, l found that wild cattle would straighten their necks and place their chin in the curved part of the yoke. When the animal moved into position, the pressure could be increased, and the head was brought up into the restrained position with very little pressure. None of these animals pulled their head out of the yoke or even tried. At all times, pressure was applied fimmly.
A wild horse may flinch and pull away from being touched by a human, similar to the reactions of some autistic children to touch. In the process of taming a wild animal, animal trainers have learned that a fimm touch calms and a very light touch tends to excite, again similar to the clinical observations of occupational therapists.
The two main methods used to tame wild horses are forced holding and gradual taming. Forced holding is quicker and more stressful than the somewhat slower gradual taming process.
Forced holding is similar to holding therapy for autistic children (Welch 1983). Gentler methods of holding therapy are also effective for increasing eye contact and interest in humans (Powers and Thorworth 1985).
The forced holding procedure is done quietly and gently, and care is taken to avoid excitement. The horse is securely tied or held in a livestock restraint device. The horse is held tightly and is unable to kick or thrash. During the restraint period, the trainer strokes and pets all parts of the animal's body and talks to it gently. Deep touching of every part of the animal's body is the key component of the taming procedure. The animal is released once it is nonresisting. Sessions seldom last more than one hour. Good horse trainers use forced holding only on very young animals. A significant disadvantage of this procedure is that forced restraint is stressful.
The taming approach is conducted more gradually. Horse trainers have found that nervous horses become easier to handle if they are rubbed and brushed over all parts of their bodies (Tellington-Jones and Bums 1985). The horse may flinch at first, but gradually will start to relax when stroked. Similar to the autistic child who is initially aversive to touching and then finds that touching becomes pleasurable, a horse will show a behavioral change such that a stimulus that was once actively avoided is now actively sought.
In animals, taming can proceed to the point of allowing the use of a deep touch pressure machine. Sheep can be trained to enter a device similar to the squeeze machine repeatedly and voluntarily for phammacological studies (Grandin 1989). As with humans, the sheep were introduced gradually to the device. At first, the sheep just stood in it, and subsequently pressure could be applied for increasing amounts of time.
SUGGESTIONS FOR THERAPISTS
In working with children, we have found that 5 minutes of sustained use of the squeeze machine is the minimum typically required to obtain a readily detectable calming effect.
We would suggest that use of the machine should never be forced, though strong encouragement is needed to overcome the approach-avoidance features associated with factual defensiveness. Therapists who work with tactually defensive children find that they are better able to tolerate touching that they have initiated (Key 1989). At times, it is useful to encourage such a child to use the machine for at least the minimal 5 minutes in order to ensure a noticeable effect. We have observed two basic ways that children and adults approach the machine. The pressure-seeking type immediately will start using the machine, and use it readily with little encouragement. Children with attention-deficit hyperactivity disorder typically fit in this category. In contrast, some autistic children have a high degree of factual defensiveness, so that it is difficult for them to overcome their initial aversion to touch; they will require more encouragement. Use of the machine should never be forced, but the therapist must be "gently insistent" to coax a tactually defensive client to use it.
Clients should be discouraged from sudden jerking of the pressure on and off in rapid sequence. Some people may want to increase and decrease the pressure slowly, which may help them to remain in the machine for longer periods of time. The use of slowly varying deep touch pressure should be allowed.
Margaret Creedon (personal communication 1989) has suggested that users show two pattems: sustained squeezers, and intermittent squeezers who continually squeeze it up and release it. It is possible that the intemnittent squeezers may have greater factual defensiveness than sustained squeezers, and may need encouragement to learn to tolerate the pressure.
In teaching new users to operate the machine, it is important that the therapist who demonstrates the machine really like to get in the machine. If he or she is uncomfortable or claustrophobic, the fear will be communicated to the child. I often have induced a tactually defensive child to use the machine, even after attempts by others had failed, because they could see that I enjoy it. For tactually defensive children, the therapist may need to demonstrate use of the machine repeatedly, so that they can see that it will not cause them harm. After the child becomes ac customed to the machine, he or she usually can use it voluntarily without further demonstration by the therapist.
It is essential that the machine is adjusted to properly fit the child. The side boards must be adjusted so that the V-shape supports the body, but there still must be enough space for the child's knees. Proper adjustment will enhance the effect of the machine because the pressure will be applied more evenly.
Although the squeeze machine can be used for younger children, there are many easy methods for applying deep pressure stimulation to children under the age of 5: rolling up in gym mats, "mat sandwiches," and resting under a pile of beanbag chairs. It is simply impossible to hold older children securely using these altemative methods. Two holding therapy successes have been reported by parents, and both involved young children (Randall and Randall 1989, Stribling 1989).
The squeeze machine may be most useful for older children or adults. In older children and adults, the squeeze machine can apply considerable amounts of pressure. The device is also available for use at any time. Older children and adults often feel embarrassed playing "children's games" with the therapist and prefer to use the squeeze machine in privacy.
Children with ADHD are often strongly attracted to the machine. There are suggestions that the use of the machine may allow reduction in the dose of psychostimulant required to treat these children.
It appears that the squeeze machine may be beneficial to some children with autistic disorder or attentiondeficit hyperactivity disorder, and is of little value to others. Serious side effects appear to be minimal.
In treatment of children with autism, a very heterogeneous disorder, it is well-known that a treatment that works for one individual may be useless for another. It is possible that the squeeze machine will be most beneficial to those autistic people who h ave problems with oversensitivity to sensory stimulation. These problems are perhaps due to an abnormality in the modulation of sensory inputs in several sensory modalities, and may be related to structural abnormalities in lobules V, Vl, and Vll of the v ermis of the cerebellum observed in patients with autism. Some individuals with autism, who have greater cognitive problems and relatively few sensory problems, may be less likely to benefit.
The possibility that use of the squeeze machine might allow dose reductions of psychostimulants, or conceivably, other medications, is intriguing, but awaits formal demonstration.
At present, the squeeze machine should be considered a novel treatment that has not been subjected to careful evaluation of clinical efficacy or safety. Preliminary observations in humans are encouraging, but the data are inadequate to recommend routine use in clinical care. However, a calming response to deep touch stimulation appears to be characteristic of a diversity of animals, and may represent a relatively "physiological" approach to sedation that has been overlooked by psychiatry researchers.
The squeeze machine can be obtained commercially for approximately $2000 from Therafin Corporation. Plans can also he obtained from the author 19747 Wolf Rd. P.O. Box 848, Mokena, Illinois, 60448 708-479-7300 or 800 843-4234
Ayres JA:Address reprint requests to: Temple Grandin, Ph.D.
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