Learning disabilities and the vestibular system

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Learning Disabilities
and the Vestibular System
A. Jean Ayres, PhD
Though "learning disabilities" is recognized to be an umbrella term for a
collection of diverse disorders, research studies too frequently treat the LD
group as homogeneous, comparing its functioning with that of a normal
control group. This study examines a subpopulation of LD youngsters, those
with disorders in the vestibular system which responds to gravity and changes
in one’s rate of movement. While the outcomes themselves are interesting, the
structure of the research approach has distinct advantages over the "LD
versus normal comparison" approach. - G.M.S.
An experimental group that received
sensory integrative therapy and a control
group, both identified by public schools as
having a learning disability, were studied.
All children were administered a pre-
program test battery of tactile, kinesthetic,
visual, vestibular, auditory, language,
motor, laterality, and academic achieve-
ment tests. Postprogram testing a calendar
year later to assess gains used auditory,
language, vestibular, motor, and academic
tests. A larger number of experimental
children than control children with hypo-
reactive nystagmus made greater academic
gains. It is concluded that a certain type of
vestibular disorder interferes with aca-
demic achievement and can be ameliorated
through sensory integrative therapy.
he role of sensorimotor activities in the
T amelioration of learning disorders has
received considerable discussion and
occasional testing. Most investigations have
failed to define adequately the exact nature
of that relationship in order to increase
precision in use of the sensorimotor
activities (f or a critique from this viewpoint,
see Ayres 1975). Furthermore, emphasis has
been placed on experimental testing of
hypotheses rather than on thorough
descriptive and exploratory investigations
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of the variables that underlie learning
disorders. This inappropriate focus of effort
has been noted by Bannatyne (1975).
In the meantime, evidence that the
vestibular system 0 is important in academic
learning has emerged. Kephart (1960)
recognized the significance in the child’s
relating to the earth’s gravitational force.
Since then, disorders of labyrinthine nystag-
mus in learning disabled children have been
reported by Quir6s (1967, 1976), Cheek
(1970-71), Frank and Levinson (1973), and
Ayres (1972b). Quir6s associated the vesti-
bular disorder with language development;
Cheek found both reading and arithmetic
disorders among children with irregular
electronystagmographs.
In an earlier study, learning disabled
children with what were then considered
discrete auditory-language deficits and who
received therapy to enhance sensory
integration gained more on reading scores
than did a matched control group (Ayres
1972a). The therapeutic program
emphasized individualized and carefully
controlled stimulation of the vestibular
receptive apparatus and activation of
related central nervous system mechanisms.
Results suggested an effect upon language
development by the vestibular system.
Further work at that time linked postural
response deficits, in part a function of the
vestibular system, with poor coordination
of sensorimotor functions between the two
sides of the body (Ayres 1972b).
These results, along with observations
that some learning disabled children
respond well to sensory integrative
therapy and some do not, raise the ques-
tion of which neural conditions predispose
the learning disabled child to responsive-
ness and which do not. The purpose of this
study was to answer this as well as related
questions. The approach w as to pose a series
*See glossary for definitions of this and other technical
terms used in this article.
of successive questions and obtain answers
that would, in turn, lead stepwise to further
questions and answers.
ASSESSMENT OF PARAMETERS
What measures or combination of measures
of sensorimotor and language functions can
be used to assess the neural conditions that
might predispose a child to greater
responsivity to sensory integrative therapy?
The subjects from which data were
gathered to answer this and subsequent
questions were 116 public and 12 private
school children, of which 102 were males
and 26 were females. Ages ranged from 6 to
10 years with a mean of 97.6 months and a
standard deviation (SD) of 14.3. All had
been diagnosed by the schools as learning
disabled and all were receiving special
academic help. Two major criteria were
employed by the schools in the diagnosis:
(1) academic achievement below intel-
lectual capacity, or (2) inability of the child
with average or above average intellect to
profit from placement in a standard class-
room. Behavioral factors were often
involved in the second criterion.
An initial battery of tests given to all 128
subjects included the Southern California
Sensory Integration Tests (SCSIT), the
Southern California Postrotary Nystagmus
Test (SCPNT), an intelligence test (usually
the WISC or Binet), measurements of
postural and ocular responses, and indices
of lateralization. The SCPNT measures the
duration on nystagmus following rotation, a
vestibulo-ocular reflex reflecting the
integrity of one aspect of vestibular
function. The public school children were
also administered portions of the Illinois
Test of Psycholinguistic Abilities (ITPA),
the Flowers-Costello Tests of Central
Auditory Abilities (FCTCAA), the Wide
Range Achievement Test (WRAT), the
Slosson Oral Reading Test (SORT), and a
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dichotic listening test. The dichotic listening
test presented the syllables pa, ka, ta, ba, da,
and ga in classical dichotic form, with the
exception that instead of paired responses
only one was requested.
From cluster analyses of scores on this
sample population (Ayres 1977) and
previous comparable populations (Ayres
1965, 1969, 1972c, Silberzahn 1975), five
domains of sensorimotor and language
functions were established: (1) postural-
ocular, (2) praxis, (3) auditory-language, (4)
eye-hand coordination, and (5) duration of
postrotary nystagmus. In previous sample
populations, scores on tests of visual
perception have tended to cluster, but in this
sample the five visual test scores did not
share common variance to the extent that a
strong visual factor emerged. Factor scores
were computed for each child, based on
performance in each domain of
sensorimotor function, and these factor
scores served as the basis for answering
further questions.
CONDITIONS INFLUENCING
ACADEMIC GROWTH
Most Predictive Factors. Which factor
score will best predict academic
improvement in children receiving both
sensory integrative therapy and special
education? Will this factor be the same for
children receiving special education only?
An experiment was conducted to gather the
data for answering this and subsequent
questions. From the original group of 116
children in special public school classes in
the southwestern part of Los Angeles
County, 92 were selected as either
experimental (N = 46) or control (N = 46)
and were available for posttesting. In
general, the youngest children in classrooms
for the educationally handicapped were
selected. Schools s that t provided
experimental subjects one year provided
control children the alternate y6ar of the
two-year period during which therapy was
provided. In one instance, a different school
in the same school district served as control
for the experimental group of that district.
Preprogram testing consumed the first
three months of each calendar year for all 92
of the children. One-half hour of therapy
each weekday for the 46 experimental
children followed and continued with
interruptions for summer and other
vacations until the following Christmas
vacation, resulting in approximately six
months of therapy which was timelost from
the classroom.’ The control group of 46
continued each day in their classes, thereby
receiving the equivalent in time of special
education classroom experience. Therapy
for the experimental group was individually
prescribed and executed either individually
or in pairs. It stressed vestibular, tactile, and
proprioceptive stimulation and activation
of mechanisms involving these systems.
(Vestibular and tactile stimulation are not to
be confused with perceptual-motor
training, and they should be employed only
by the specifically trained professional.)
Age, IQ, and sex of subjects in the
experimental and control groups are shown
in Table I.
A posttest battery administered
approximately one year after the initial
battery consisted of the Motor Accuracy
and Design Copying Tests of the SCSIT, the
SCPNT, the dichotic listening test, the
auditory-language subtests of the ITPA, the
FCTCAA, the WRAT, and the SORT.
Scores of the children whose ages exceeded
that of the population on which the tests
were standardized were computed by
extrapolating from the normative data. The
SD equivalent of the pretest scores on each
test were subtracted from the SD equivalent
of the posttest scores to obtain a change
score. Both pretest and posttest scores were
age-related. It is recognized that the
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TABLE 1. Age, IQ, and sex distribution of subjects in experimental and control
groups.
difficulties in obtaining precise test results
on only moderately reliable tests for
children who have attentional and behavior
problems reduce the probability of obtain-
ing significant differences between groups.
Stepwise discriminant analyses de-
termined which of the factor scores best
predicted change scores in both
experimental and control groups. In both
groups the best predictors, understandably,
were generally factor scores in the same
domain as the predicted change score. For
example, the auditory-language factor score
was the best predictor of change on the
ITPA. In the experimental group, however,
the preprogram duration of postrotary
nystagmus was the best predictor of change
in the Reading and Spelling test scores of the
WRAT and in the dichotic listening test
score. The hyporesponsive children, who
obtained a score of -1.1 SD or lower, made
greater gains than those without
hyporeactivity. The hyporesponsive
children were also more intelligent, which
might account for some of the gain. A chi
square tested the different frequency with
which the gain scores of the experimental
children with and without hyporeactive
nystagmus fell above the median gain scores
for the entire experimental group and did
not reach statistical significance. (In all chi
squares reported, Yates’ correction was
employed whenever any observed cell
frequency was less than 5 or expected cell
frequency was less than 10.) The age, IQ,
and sex of the experimental and control
subjects with and without hyporeactive
nystagmus are given in Table II.
In the control group, on the other hand,
fewer of the children with hyporeactive
nystagmus made academic gains than did
those without hyporeactive nystagmus.
Scores of 15 of 23 in the hyporeacti~~e group
and of 7 of 23 in the nonhyporeactive group
fell below the control group median change
score on the total BN’RAT. Test of the
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TABLE II. Age, IQ, and sex distribution of the experimental and control children with
and without ht~poreactive postrotary nystagmus (HPN).
TABLE III. Age, IQ, sex distribution, and number in each school or school district of
experimental and control children with hyporeactive postrotary nystagmus.
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significance of difference in frequencies
resulted in a chi square of 5.57 (p’~
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processes, although they were below age
expectations in the latter two categories. A
vestibular disorder resulting in
hyporesponsivity to rotation may present
one of the most frequently occurring and
presistent interferences with learning, but it
does not necessarily result in the most severe
academic problems seen in a special
education situation. Children with
prolonged duration nystagmus, while fewer
in number in this population, appear to have
greater and more extensive neurological
involvement as measured by this study.
Discriminant analyses were employed to
determine the variables that best differenti-
ated the three groups. The major discrimi-
nating variables, none of them favoring the
group with hyperresponsive nystagmus,
were (1) the right hand score on Manual
Form Perception of the SCSIT, (2) greater
muscle tone in the right arm, (3) Auditory
Association of the ITPA, (4) Auditory
Reception of the ITPA, and (5) Visual
Sequential Memory of the ITPA. On the
dichotic listening test, the hyporeactive
group averaged 32 correct responses out of
a possible 60, compared with an average of
25 for the hyperreactive group. The
differences suggest that the group with
prolonged nystagmus contained a number
of children with left cerebral hemisphere
dysfunction, although many of this group
appeared to have a generalized disorder. All
five of the children previously identified as
having discrete left cerebral hemisphere
dysfunction had either normal or prolonged
duration nystagmus. They vvere among the
less responsive to therapy.
These results are consistent with
experiments using cats and dogs in which
cerebral lesions resulted in increased
reactivity in nystagmus (Wycis & Spiegel
1953). Similarly, prolonged postrotary
nystagmus has been reported in children
with Down’s syndrome (Kantner, Clark,
Allen, & Chase 1976) and in cerebral palsied
children (Chee, Clark, & Kreutzberg 1976).
Hyperreactive nystagmus may be a release
phenomenon reflecting less than normal
inhibition from higher levels of the brain
upon the vestibular nuclei in the brain stem.
The major implications of a comparison of
children with and without hyporeactive
nystagmus are: (1) the hyporeactive
children are apt to appear to be more
normal than other learning disabled
children and (2) the hyperreactive children
are more apt to have cerebral and/or more
generalized dysfunction.
THE VESTIBULAR SYSTEM AND
LANGUAGE PERFORMANCE
Is the vestibular system related to language
development? Few doubt the critical role of
language in academic achievement. At the
same time, observations have suggested that
these auditory-language disorders are not
discrete but a manifestation of either more
extensive dysfunction, such as one in the
vestibular system or one in the left cerebral
hemisphere.
Previous studies (Quir6s 1967, Ayres
1972a) have linked language and the
vestibular system. Results reported above
suggest a causative relationship between
vestibular disorder and academic
performance involving written language. It
is more difficult to establish a relationship
with oral language. The 23 experimental
children with depressed nystagmus gained
more on the ITPA tests than did the 23
control children, but the difference did not
reach statistical significance. Within the
experimental I group, those with
hyporeactive nystagmus showed greater
gains on Verbal Expression than did the
nonhyporeactive experimental children,
but the chi-square level of significance was
only .17. On the other hand, there was a
statistically significant difference (pthe research literature on
the ITPA by Newcomer and Hammill
(1975) failed to indicate a close relationship
between ITPA performance and academic
problems in reading, arithmetic, or spelling.
This finding suggests that oral language
performance as measured by the ITPA at
school age is not closely related to handling
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written language as it is encountered in
reading and spelling. Rather clinical im-
pression and evidence favor an association
between the vestibular system and/or
sensory integrative therapy on the one hand
and the development of vocalization and
fluency of speech on the other, as opposed
to later tested, more cognitive skills (Quir6s
1967, 1976). The frequency of hyporeactive
nystagmus was not less among learning
disabled children with age-adequate
language scores: there was a greater
frequency of, hyporeactivity among the
brighter children.
ACKNOWLEDGMENTS
This research was supported by grants from the Center
for the Study of Sensory Integrative Dysfunction and
the Valentine-Kline Foundation. The Churchill School
of New York City and the public school districts of
Manhattan Beach City, Redondo Beach City, and
Torrance Unified, all in Los Angeles County,
cooperated in this study. Florence Cook Davis and
Edu:ard T. Dauaon assisted in testing and treating.
Mary A. Silberzahn assisted in postprogram testing.
The dichotic listening tape was provided by Richard
Harshman of the Phonetics Laboratory, University of
California, Los Angeles. Thomas J. Reynolds and
Robert Cudeck served as statisticians.
ABOUT THE AUTHOR
A. Jean Ayres, adjunct professor of occupational therapy at the
University of Southern California, has devoted much of her
professional life to studying neurological disorders and
developing procedures to ameliorate their effects. She is in
private practice at 1518 Cabrillo Ave., Torrance, Calif. 90501.
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