Autism - Scientific Background
Autism is a developmental disorder characterized by limited personal communication and social interaction, by an unusual range of behaviors and in many cases limited language skills. Research on the causes of autism has drawn a lot of attention and funds, yet little progress has been achieved in understanding its mechanisms.
In spite of the enigmatic nature of autism, some consensus statements concerning affected people do exist, most noteworthy Sensory Perception (SP), also included as a diagnostic criterion in APA’s Diagnostics and Statistics Manual (DSM) (1).
Sensory functions of people with autism, and in particular their ability to selectively attend to specific stimuli, are impaired. Abnormalities in hearing, vision and other senses have been reported. Since there is no evidence that the peripheral sensory organs (eyes, ears) are involved, the site of the impairment seems to be in a central sensory processing location (2).
SensPD’s technology is based on these findings and the understanding that SP issues are the cause and not the result of autism.
The following is a review of observable (and sometimes measurable) phenomena associated with autism:
1) Attention Shift delay – a delayed response to interrupting vocal stimulus or vocal attention shift delay (3)
2) Auditory Brain Stem Response (ABR) – reflects the auditory-evoked neural signal as it passes from the inner ear through the brain stem. The brain stem’s response to speech is a marker of auditory processing. Indeed, children with speech processing deficiencies show a specific deficiency in the neural encoding of acoustic features as was demonstrated already in 2005 (4).
3) Reduced magnitude and fidelity of speech-evoked responses – ASD subjects test results in background noise showed marked degradation of these parameters. Language ability was significantly related to the degradation of synchrony in noise (5).
4) Visual search superior performance (5).
5) Increased pitch variability in children with autism (5).
6) Abnormal transient pupillary light reflex (5).
Focusing on hearing, the most social of the senses and specifically on the intriguing phenomenon of Oto-Acoustic Emissions (OAE) (6), a model was built that puts the outer hair cells (which generate OAE) response, as the centerpiece of sensory processing.
A review of stochastic signals generated in the neural system and their effect on sensory information processing have shown that stochastic neural activity initiated by the outer hair cells (OAE) influences computations in other brain sites. The neural activity associated with audible sound frequencies implies that the influence of cells located in the inner ear is widespread (7).
Thus, it was demonstrated that the same auditory noise can enhance the sensitivity of tactile, visual, and proprioceptive system responses to weak signals. Specifically, the effective auditory noise significantly increases tactile sensations of the finger, decreased luminance and contrast visual thresholds and significantly changed EMG recordings of the leg muscles during posture maintenance (8).
Frith and Baron-Cohen hypothesized that the main abnormality in autism is a deficiency in the ability to construct a “theory of other minds (TOM)” (9). They argue that specialized neural circuitry in the brain allows formulation of sophisticated hypotheses about the inner workings of other people’s minds. These hypotheses, in turn, enable useful predictions about others’ behavior. TOM and other explanations imply that the sensory system provides reliable information that is than mis-interpreted. In SensPD we believe that the failure of SP is behind TOM and other similar theories.
SensPD’s inventive step is the association of OAE measurement with SP and its performance, that is why SensPD’s approach allows for a very early objective diagnosis of autism.
American Psychiatric Association (APA), Diagnostic And Statistical Manual Of Mental Disorders 5th edition: https://dsm.psychiatryonline.org/doi/book/10.1176/appi.books.9780890425596
DeBoth, K.K. & Reynolds, S. (2017). A systematic review of sensory-based autism subtypes. Research in Autism Spectrum Disorders, 36, 44–56.
Courschesne E. 1987. A neurophysiological view of autism. In: Neurobiological issues in autism. Schopler E and Mesibov GB, editors. New York: Plenum. 285 p.
Russo N, Nicol T, Trommer B, Zecker S, Kraus N. 2009a. Brainstem transcription of speech is disrupted in children with autism spectrum disorders. Dev Sci 12(4):557-67.
Baum, Sarah H., Stevenson, Ryan A, Wallace, Mark T. (2015). Behavioral, perceptual, and neural alterations in sensory and multisensory function in autism spectrum disorder. Progress in Neurobiology 1394, 1-21.
Kemp, David T. (2002), Otoacoustic emissions, their origin in cochlear function, and use. British Medical Bulletin 2002;63: 223–241
Mori T and Kai S. 2002. Noise-induced entrainment and stochastic resonance in human brain waves. Phys Rev Lett 88(21):218101-4.
Lugo E, Doti R, Faubert J. 2008. Ubiquitous cross-modal stochastic resonance in humans: Auditory noise facilitates tactile, visual and proprioceptive sensations. PLoS ONE 3(8):e286
Baron-Cohen S, Leslie AM, Frith U. 1985. Does the autistic child have a "theory of mind"? Cognition 21(1):13-125.