Sensory Theory In Autism Makes Sense - A Brief Review Of The Past And Present Research
There is no real understanding regarding sensory processing. We need more research on sensory theory in autism to help individuals with autism correctly.
Author:Suleman ShahReviewer:Han JuFeb 20, 20245.1K Shares171.5K Views
Unusual responses to sensory stimuli were noticed from the very beginning of the official historyof autism, and the pioneering research started in the 1960s.
Since then, for many decades, sensory hypotheses have not been considered important because there has been no empirical evidence for this assumption.
At present, however, we witness an explosion of interest in sensory perceptual issues.
The sensory perceptual theory of autism is steadily taking shape, incorporating findings from other related fields, and producing a framework for studying sensory differences in autism, their impact not only on the behaviors of individuals with autism spectrum disorder (ASD) but also on their:
- language
- cognition
- social impairments
As a review of all the available literature is beyond the scope of this paper, only a selection of research studies relevant to some methodological and conceptual problems of sensory perception in autism is included.
This review challenges the conventional interpretation that gives primacy to social communication problems.
The recognition of sensory perceptual differences in autism can assist in improving diagnostic instruments and provide information about appropriate support for each individual.
First Sensory Hypotheses
Leo Kanner and Hans Asperger described bizarre reactions of their patients to:
- sound
- touch
- sights
- taste
- smell
Kanner discussed it in his article Autistic Disturbances of Affective Contactpublished in the journal Nervous Childin 1943.
Asperger wrote about it in Die “Autistischen Psychopathen” im Kindesalter [The “Autistic Psychopaths” in Childhood]published in Archiv für Psychiatrie und Nervenkrankheiten (European Archives of Psychiatry and Clinical Neuroscience)in 1944.
His work also goes by this title: “Autistic Psychopathy” in Childhood.
Based on their clinical observations, which they discussed in their study published in the journal The Psychoanalytic Study of the Childin 1949, Paul Bergman and Sibylle K. Escalona presented a hypothesis.
They put forward a sensory hypothesis to explain the development of autism: autistic children start lifewith a higher degree of sensory sensitivity, which makes them acquire defensive strategies to protect themselves from overload, which, in turn, results in developmental distortions that are reflected in autistic conditions.
In a study published in the journal in JAMA Psychiatry(when it was still called Archives of General Psychiatry) in 1960, the author, Herbert H. Eveloff, described severe perceptual difficulties encountered by children with autism.
In her study published in Cerebral Palsy Bulletinin 1961, Dr. Mildred Creak, included unusual sensory perceptual experiences in the list of core symptoms of autism.
In his book Infantile Autism (1964), Dr. Bernard Rimland emphasized the importance of exploring perceptual abilities of autistic children.
In her study published in the Journal of Child Psychology and Psychiatryin 1969, Lorna Wing showed that autistic children have significantly more sensory perceptual problems than both typically developing children and children with Down’s syndrome and included sensory perceptual features into “basic impairments in autism.”
In his study published in the journal Comprehensive Psychiatryin 1969, Dr. Edward M. Ornitz researched disorders of perception common in autism and extended the notion of a disorder of sensory processing to the notion of sensory and information processing.
This approach allowed Dr. Ornitz to clarify and identify separate stages and functions of sensory perception and consider information processing in termsof more discrete functions, such as:
- attention
- memory
- learning
It was suggested that autism might be identified in young children if we look at very specific and easily described behaviors caused by sensory perceptual differences.
For example, before the age of 6, these behaviors were observed with almost the same frequencies as behaviors related to social and communication impairments.
In his book The Ultimate Stranger (1974), Dr. Carl H. Delacato hypothesized that unusual sensory experiences were a primary characteristic feature of autism, which were able to account for the basic symptoms of the condition considered to be essential in the diagnostic classifications.
This, in turn, results in obsessive or compulsive behaviors and social and communication problems, making the more commonly accepted criteria, in fact, secondary developmental problems.
It was started by American occupational therapist Anna Jean Ayres (1920-1988), who is the author of the book Sensory Integration and the Child (1972).
Ayres formulated the theory of sensory integration (SI) dysfunction to describe a variety of neurological disorders.
This theory attempted to account for the relationship between sensory processing and behavioral deficits in different developmental disorders including autism.
Ayres originally limited her investigation to three senses:
- tactile
- vestibular
- proprioceptive
Then she identified the problems in them as:
- tactile defensiveness
- gravitational insecurity
- postural insecurity
Unlike Delacato’s concepts of “hyper/hyposensitivities,” describing the inner experiences, Ayres defined SI deficits mostly in terms of behavioral reactions.
For example, tactile defensiveness is defined as avoiding or negative reactions to non-noxious tactile stimuli, manifested in “fright, flight, or fight” response or reaction.
Recently, OT researchers have suggested the updation of terminology used in SI and proposed “sensory processing disorder” as a global umbrella term that includes three primary groups:
- sensory modulation disorder
- sensory discrimination disorder
- sensory-based motor disorder . . .
. . . and the subtypes found within each.
Another model of sensory processing, introduced by Winnie Dunn in her study published in American Journal of Occupational Therapyin 2001, aims to account for the nervous system’s thresholds for acting and the person’s propensity for responding to those thresholds:
- low registration
- sensory seeking
- sensory sensitivities
- sensory avoiding
Critical Assessment Of The First Hypotheses
In 2005, Sally J. Rogers and Sally Ozonoff published a critical analysis (appears in the Journal of Child Psychology and Psychiatry) of controlled experimental laboratory investigations published since 1960 - a total of:
- 48 empirical papers
- 27 theoretical or conceptual papers
Rogers and Ozonoff concluded that the empirical information available at the time is not supportive of many current theories concerning the specificity of sensory dysfunction in autism.
They pointed out that empirical work in the areas of cognition and communication provides “far more definitive information about the nature of autism in those domains than the sensory area.”
Their conclusions were based on:
a. the lack of good evidence that ‘sensory symptoms’ differentiate autism from other developmental disorders;
b. some groups of children (with fragile X syndrome and those who are deaf-blind) appear to demonstrate higher rates of sensory-based behaviors than children with autism; and
c. the analysis of evidence relevant to the theories of sensory dysfunction in autism (over-arousal and under-arousal theory) provides very little support for hyperarousal and failure of habituation in autism.
Rogers and Ozonoff also commented on perceptual inconstancy and crossmodal impairment theories as not supported by the research findings available at the time.
The aim of this review is to discuss the past and present developments in sensory theory in autistic individuals.
Materials And Methods
To re-examine some methodological and conceptual problems related to the research of sensory perception in autism, the research studies have been selected on the basis of addressing the limitations of the studies analyzed in the review, such as a very restricted choice of the phenomena for examination (typically limited to over/hyper-, under/hyporesponsiveness and sensory seeking), while other sensory phenomena common in autism have not been explored.
As a result, the fundamental features of sensory processing (common in autism) have been rarely investigated, and many variables have not been taken into account.
For example, the person can react to the same stimuli differently in different situations (so, the results of the laboratory tests do not always provide a full picture).
The first-hand account of people with autism is a very important source of our understanding of the problems they experience, and they may have greater validity than our assumptions based on behaviors we observe.
Other theories (often omitted from critical reviews) have been analyzed.
Limited space means that only a selection of the research studies relevant to the sensory perceptual issues in autism has been included.
Recent Developments And ‘New Old’ Hypotheses
Sensory characteristics of autism seem to be primary for many autistic people.
Such features as, for example, unusual responses to sensory stimuli, are often seen as the core description of autism.
Besides, from the autistic perspective, these responses are “normal” (not “unusual” or “bizarre”) because they are caused by different sensory perceptual processing.
Many authors consider autism as largely a condition relating to sensory processing and suggest that the true deep-rooted cause of all social and communicative problems is of a sensory perceptual nature.
They identify the problems they experience as differences/disturbances in their sensory perception and information processing.
In her book Thinking in Pictures (1995), American academic and animal behaviorist Mary Temple Grandin put forward a hypothesis that there is a continuum of sensory processing problems for most autistic people, which goes from fractured disjointed images at one end to a slight abnormality at the other.
During the last decade, there have been an increased number of research publications on the subject.
The scope of the research (both quantitative and qualitative) differs considerably, but the majority of the publications provide robust and validated findings that support the sensory perceptual theory in autism.
Some studies produced results that have not been replicated, and a few others, having studied certain phenomena in six to eight individuals with Asperger syndrome, overgeneralize their findings to cover the whole spectrum.
Many research studies have investigated single sensory modality, for example, auditory discrimination and auditory sensory behaviors were examined by Catherine R. G. Jones and her co-authors in their study published in the journal Neuropsychologiain 2009.
In their study published in the journal Psychophysiologyin 2013, Helen Clery and her co-authors examined atypical visual change processing. Other studies examined multimodal sensory difficulties that are quite common in autism.
In their study published in the journal Experimental Brain Researchin 2010, Jennifer H. Foss-Feigher and her co-authors investigated the differences in multisensory temporal function in ASD.
Their findings suggest that autistic children have altered multisensory temporal function.
A research report (containing the results of two studies) by Susan R. Leekam and her co-authors was published in the Journal of Autism and Developmental Disordersin 2006.
It confirmed that sensory abnormalities are pervasive, multimodal, and persistent across age and ability in children and adults with autism.
It also verified that individuals with autism have multimodal sensory difficulties.
Other findings suggest that:
a. the relationship between sensory responsiveness and other autistic traits is very important
b. addressing sensory issues in children with autism is critical
The sensory and motor differences found between typical and high-risk infants (infant siblings of autistic children) suggest that early screenings for ASD should include the examination of sensory and motor behaviors
Ashley E. Robertson and David R. Simmons, in their study published in the Journal of Autism and Developmental Disorders in 2013, provided the data that indicate a strong link between sensory processing and autistic traits in the general population, which potentially implicates sensory processing problems in social interaction difficulties.
Some studies reveal that sensory processing problems differ between clinical subgroups of ASD.
Sensory difficulties have been assessed in people of different ages.
For example, 20-month-old to 54-month-old children were grouped based on the degree of autistic symptoms and cognitive levels.
The most affected modalities in the whole group were pain and hearing.
The researchers report that children in the most typical autism subgroup (nuclear autism without learning disability) had the highest number of affected modalities.
The children with “autistic features” had the lowest number of affected modalities.
However, there were no group differences in the number of affected modalities between groups of different cognitive levels or levels of expressive speech.
These findings show that sensory problems are very common in young children with autism.
Jill Ashburner and her co-authors, in their study published in Australian Occupational Therapy Journalin 2013, investigated the responses to sensations in a group of young people with autism.
Their research showed that participants experienced:
- a heightened awareness of and difficulty in filtering extraneous sensory input
- high level of movement seeking
- over-focus on salient sensory input
- a preference for predictable and controlled sensory input
Laura Crane and her co-authors, in their study published inthe journal Autismin 2009, suggested that unusual sensory processing in autism extended across the lifespan.
Adults on the autism spectrum can experience very different yet similarly severe sensory processing abnormalities.
In their study published in the journal Frontiers in Integrative Neurosciencein 2012, Anne M. Donnellan and her co-authors challenged the conventional interpretation that gives primacy to social communication and imaginative play.
They argued that children and adults with autism may have unrecognized and significant sensory and movement differences.
Discussion
The data from the cited studies also raise some very important theoretical questions.
In his study published in the journal Behavioral and Brain Sciencesin 1999, Lawrence W. Barsalou argues that cognition is inherently perceptual, sharing systems with perception at both the cognitive and neural levels and that a perceptual theory of knowledge can implement a fully functional conceptual system.
Thus, the boundaries of neuroscience are changing, and “the distinction” between sensory and cognitive function becomes increasingly unclear. Disorders that were previously considered “cognitive” may be “relabeled.”
The differences of sensory processing may lead to different routes of cognitive and language development, which are eventually reflected in different systems of communication and social interaction.
It is hardly surprising that autistic individuals try to bring predictability and some order in the chaos in which they live, bearing in mind their differences in:
- perceptions
- cognitive mechanisms
- the adaptive strategies they acquire
Stereotyped behaviors are seen by many autistic people as their compensatory strategies to regulate their sensory systems and cope with sensory overload.
Unlike the most recent trend to interpret stereotypies as attempts to communicate, it is not always necessarily so, and there may be other reasons, different for each individual and for different situations.
Self-stimulatory behaviors may serve several purposes, and one and the same behavior may have different underlying causes.
Routines and rituals, typical to the condition, bring some predictability to an otherwise incomprehensible world.
The importance of theoretical and conceptual constructs is undeniable.
In their study published in the Journal of Autism and Developmental Disordersin 2009, Sue Gerrard and Gordon Rugg point out theoretical modeling weaknesses (despite abundant data available) and inadequately tested hypotheses.
As sensory problems (though widely reported) remain largely unexplained by existing models, the authors suggest a re-examination of causal modeling.
Their analysis supports a heterogeneous causal model for autistic characteristics.
Gerrard and Rugg proposed that the development of a standardized framework for analyzing autistic features would facilitate:
- the identification of subgroups
- the location of biological markers for genetic variation
This approach supports a neuroconstructivist model, indicating that sensory abnormalities:
- disrupt compilation of complex skills;
- impact on synaptogenesis, synaptic pruning, and myelination; and subsequently
- manifest themselves as autistic behaviors.
Gerrard and Rugg believe that such a model explains some structural and functional brain abnormalities and many of the:
- perceptual;
- cognitive; and
- attentional features of autism.
They disagree with the conclusion that sensory impairments are not a distinguished characteristic of autism and cite a body of research that indicates that a possible cause of autistic characteristics by sensory abnormalities cannot be ruled out.
Gerrard and Rugg persuasively argue (supporting their views with the empirical research evidence) that “a deficit in one submodality might make only a small contribution to overall primary processing in this mode, but could play a more significant role in certain aspects of higher-level processing.”
They conclude that certain sensory abnormalities can produce behaviors that meet clinical criteria for diagnosis of autism.
In addition, whether sensory deficits arise peripherally or centrally, they not only significantly affect cognitive and social functioning but also can be experienced as far more debilitating than social interaction and communication.
There are some theoretical models that can account for the sensory development in autism.
For example, in their study published in the journal Genes, Brain, and Behaviorin 2003, John L. R. Rubenstein and Michael M. Merzenich devised a model for autism that could:
- explain the symptoms;
- identify and explain the specific features of emotional, cognitive, and language development; and
- suggest their underlying cause
Rubenstein and Merzenich propose that efforts to understand autism origin should be - along with development of social behaviors - on the development of neural circuits and systems that underlie language processing, that is:
- audition
- language comprehension
- speech production
- verbal memory
- cognition
Some other studies confirm that autistic individuals appear to have a range of perceptual processing abnormalities/differences, expressed especially strikingly by a hypersensitivity to auditory and tactile stimuli.
Such studies indicate that the auditory environment has a paramount impact on the progression of the fundamental maturation and specialization of the primary auditory cortex.
They also implicate a number of specific sensory factors that could potentially amplify or otherwise modulate developmental progressions.
The comparative research of minicolumns in the brains of non-autistic and autistic individuals has revealed that in non-autistic neocortex:
a. information is transmitted through the core of the minicolumn
b. information is prevented from activating neighboring units by surrounding inhibitory fibers
Minicolumns in autism, however, are:
- smaller
- more numerous
- have abnormal structure
So, stimuli are no longer contained within them but rather overflow to adjacent units; thus, creating an amplifier effect. Inhibitory fibers just do not cope with this flow.
In their study published in the journal Frontiers in Neurosciencein 2007, Henry Markram and his co-authors propose a unifying hypothesis of autism, which they call “the intense world syndrome.”
It is where the core neurological pathology is excessive neuronal information processing and storage in local circuits of the brain, which gives rise to hyperfunctioning of the most affected brain regions.
According to the authors, the vast autism spectrum could be explained by the specific degree to which this hyperfunctional molecular syndrome is active in different areas of the brain, which could depend on the precise stage of development that the brain is exposed to:
- a triggering insult
- the type of toxic insult
- the presence of any predisposing genes
Thus, all features of autism can be seen as rooted in sensory overload experienced by individuals with autism. Such features include:
- social interaction impairments
- communication and language problems
- cognitive functioning
- repetitive behaviors
Autistic people perceive, feel, and remember too much.
Faced with bombarding, confusing, baffling and often painful environments, autistic infants withdraw into their own world by shutting down their sensory systems.
It brings unfavorable consequences for their social and linguistic development.
Repetitive behaviors are seen as an attempt to bring order and predictability to their environment, which may include:
- rocking the body
- flapping hands
- head-banging
The Swiss researchers have provided a strong neurological evidence of the presence of overload in individuals with autism.
Contrary to most neurological studies that describe underconnectivity/hypoactivity/deficits of connectivity of the autistic brains, the research by Markram and his co-authors has established that the autistic brain is, in fact, overperforming.
They cite reduced activation reported in attention tasks as well as in speech recognition and generation but normal to increased activation during motor tasks.
In general, functional imaging studies seem to suggest that higher-order brain areas are not fully activated, being disconnected from lower-order sensory areas, while these lower-order sensory areas may be even hyperactivated.
Hyperreactivity and hyperplasticity mean that minicolumns have a higher than normal capacity for processing information.
Excessive processing of the sensory input in the microcircuits leads, in turn, to exaggerated perception, producing extremely intense images, sounds, smells, etc.
This sensory overload, combined with inability to filter information, causes autistic children to withdraw and miss the opportunity to develop a shared conceptual understanding of the world.
In this view, ASDs are disorders of hyperfunctionality as opposed to disorders of hypofunctionality, as is often assumed.
Excessive neuronal processing may make the world painfully intense when the neocortex is affected and even aversive when the amygdala is affected.
This research confirms the findings and theories of sensory perceptual cause(s) of autism that were introduced in the last century.
The criteria of core features can be applied to sensory perceptual issues in autism:
a. Specificity
Characteristics specific only to autism, but not to other disorders.
Research has shown that sensory perceptual profiles of autistic people differ from those with other disabilities.
b. Universality
Features present in all individuals.
It may be seen in their ‘autistic thinking’ and behavioral responses, especially if we include not only hypersensitivities as indicators of “sensory characteristics” but other quite common in autism phenomena
c. Primacy
Early in development.
“Sensory symptoms” can be detected in early development - much earlier than social and communication impairments - if we know what to look for and overcome the traditional “hypersensitivity/defensiveness approach.”
For example, “seeming deafness” or “fascination with sensory stimuli” is “visible” at the age of 9-12 months or even earlier.
There is research evidence that does indicate that sensory perceptual differences may be among the first signs of autism in young children.
However, these early signs, especially those occurring in the first year of life, are often missed and become apparent only retrospectively.
These autistic “sensory symptoms” observed during the first years seem to persist into the second year of life.
At some point of their development, autistic toddlers and preschool children display atypical sensorimotor behaviors, including:
- heightened sensitivities (across sensory modalities)
- reduced responsiveness (across sensory modalities)
- motility disturbances, such as stereotypies
Numerous individual differences, indicating possible subtypes based on different patterns of sensory perceptual problems have been reported.
d. Account for other characteristics
Should connect and explain biological/genetic, cognitive/psychological, and behavioral manifestations and the diversity of manifestationof autism in different individuals.
Conclusion
Sensory theories of autism have been discussed from the first description of the condition.
However, the available empirical information did not support them because of the lack of appropriate theoretical and clinical constructs that instructed the research investigation in the past (e.g., limiting autism to very few phenomena).
The research studies aiming to explain the role of sensory perception will generate more specific hypotheses about the sensory perceptual processes and their mechanisms in autism.
Better understanding of sensory processing in autism will assist in:
- improving diagnostic instruments
- distinguishing sensory perceptual subtypes of autistic individuals
- providing appropriate choices of help needed by each particular individual
As sensory perceptual profiles of autistic individuals differ considerably, it is no wonder that certain sensory-based approaches will work for some individuals while making no difference to others.
The recognition of sensory perceptual differences (both strengths and weaknesses) is a new (but old) field.
Unfortunately, many professionals are unaware or unknowledgeable about these issues, how to recognize them and what to do about them.
Isn’t it time at last to listen to those who live with autism and consider the problems they identify as the primary ones instead of going in the opposite direction?
More studies, therefore, for sensory theory in autism.
Suleman Shah
Author
Suleman Shah is a researcher and freelance writer. As a researcher, he has worked with MNS University of Agriculture, Multan (Pakistan) and Texas A & M University (USA). He regularly writes science articles and blogs for science news website immersse.com and open access publishers OA Publishing London and Scientific Times. He loves to keep himself updated on scientific developments and convert these developments into everyday language to update the readers about the developments in the scientific era. His primary research focus is Plant sciences, and he contributed to this field by publishing his research in scientific journals and presenting his work at many Conferences.
Shah graduated from the University of Agriculture Faisalabad (Pakistan) and started his professional carrier with Jaffer Agro Services and later with the Agriculture Department of the Government of Pakistan. His research interest compelled and attracted him to proceed with his carrier in Plant sciences research. So, he started his Ph.D. in Soil Science at MNS University of Agriculture Multan (Pakistan). Later, he started working as a visiting scholar with Texas A&M University (USA).
Shah’s experience with big Open Excess publishers like Springers, Frontiers, MDPI, etc., testified to his belief in Open Access as a barrier-removing mechanism between researchers and the readers of their research. Shah believes that Open Access is revolutionizing the publication process and benefitting research in all fields.
Han Ju
Reviewer
Hello! I'm Han Ju, the heart behind World Wide Journals. My life is a unique tapestry woven from the threads of news, spirituality, and science, enriched by melodies from my guitar. Raised amidst tales of the ancient and the arcane, I developed a keen eye for the stories that truly matter. Through my work, I seek to bridge the seen with the unseen, marrying the rigor of science with the depth of spirituality.
Each article at World Wide Journals is a piece of this ongoing quest, blending analysis with personal reflection. Whether exploring quantum frontiers or strumming chords under the stars, my aim is to inspire and provoke thought, inviting you into a world where every discovery is a note in the grand symphony of existence.
Welcome aboard this journey of insight and exploration, where curiosity leads and music guides.
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