Introduction

Multisensory integration, or the simultaneous use of different sensory modalities, is a crucial aspect of our daily lives and ability to interpret and react to the world. This multisensory perception enhances our efficiency in responding to environmental stimuli (4:23). For example, the olfactory system can detect the smell of smoke, but you also need to hear burning sounds and see a light to locate its source (5:30). Understanding how sensory perception influences pain, behaviors, and ability to function is critical in ensuring the best possible care for autistic individuals. 

Sensory Modulation Dysfunction and Pain Perception, by Dr. Tami Bar-Shalita

When our reactions to stimuli hinder our general ability to function, this may indicate Sensory Modulation Dysfunction (SMD) (7:16). Sensory over-responsiveness (SOR), a type of SMD, occurs when the responses to ordinary, non-painful stimuli are amplified and cause suffering and pain, thereby reducing one’s ability to function efficiently (7:40). Bar-Shalita defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage.” She explains the pathological nature of chronic pain and asserts the need to study pain within the lens of SMD (9:30).

Study 1: Pain Perception and Brain Activity in Individuals with Sensory Over-Responsiveness

Bar-Shalita and her colleagues tested pain perception (in a controlled lab setting) in neurotypical individuals with SOR. Participants reported higher pain intensity and significantly less pain reduction over time than those without SOR (10:20). These differences in perception also manifest as imbalances in excitatory and inhibitory (E/I) responses in the brain. Bar-Shalita outlines the SMDolor Model and notes that hypersensitivity to pain could be a predisposing factor in chronic pain development (13:00). 

Historical context of autism and pain

Historically, autistic people were thought to be hypo-sensitive (indifferent) to pain based on the frequent presentation of self-injurious behaviors (SIB) (14:30). Bar-Shalita discusses research that shows reduced pain sensitivity in autistic children and a high prevalence of autism in chronic pain clinics (15:20). This evidence, the speaker asserts, suggests an ongoing misdiagnosis of chronic pain in autism and vice versa. She underscores that when left undiagnosed in autism, chronic pain can lead to compromised health care and pain treatment neglect (16:30). 

Study 2: Pain ratings of suprathreshold stimuli

Using heat pain stimuli in the lab, Bar-Shalita and her team conducted the most extensive pain study in autism to date. They found that autistic individuals with SOR tend to be hypersensitive to pain and do not show the same pain reduction over time compared to the neurotypical group (17:00). The study also found that autistic individuals who take psychiatric medication displayed higher scores on the Sensory Responsiveness Questionnaire (18:20). Autistic participants with SOR reported higher anxiety and ranked higher on the Autism Quotient and the World Disability Schedule. Bar-Shalita concludes that the symptoms severity of autistic people with SOR is higher compared to those without SOR” (20:00). 

Qualitative Exploration of Pain Experience, by Merry Kalingal Levi

Study 3: Qualitative exploration of pain experiences in autism

Per the multidimensional nature of pain experiences, Kalingal Levi and her team conducted a qualitative study to compare with the quantitative findings (21:00). They employed a phenomenological approach to explore the experiential aspects of pain perception in everyday lived experiences (21:35). Four main themes arose: pain sensitivity, pain awareness, pain communication, and pain awareness solutions (22:30). Although there was heterogeneity in the type of pain processing (hypo- vs. hypo-), identifying the existence (23:25), nature (23:45), and severity (24:10) of pain were common issues across the study group (23:20). 

Kalingal Levi explains that difficulties with pain awareness often hinder effective communication or expression of pain experiences for autistic individuals (24:40). Participants recounted situations where they or their physicians did not comprehend the seriousness of pain and, therefore, were not given proper treatment (25:00). Participants in the study suggested creative aids, such as booklets with tags and pictures, to help them recognize and convey their pain experiences. They also emphasize the need for doctors to be willing to explore what pain is and how it’s perceived individually (25:30). The research findings underline that difficulties in pain awareness are a fundamental aspect of pain experience in autistic individuals. The speaker restates the need for intensive investigation into this new area of study and urges the medical community to adopt the changes in communication and care environments cited in their research (27:00). 

Neurophysiology of Pain in Autism, by Dr. Yelena Granovsky

Study 4: EEG activity in autism

Granovsky outlines her team’s recent study on spontaneous electroencephalogram (EEG) activity in autistic individuals (28:30). Results showed that autistic individuals have enhanced activity in EEG bands responsible for physiological regulatory mechanisms and limbic system activity (29:45). Specifically, young autistic children exhibited enhanced activity in both slow Delta and Theta EEG bands, a departure from the U-shaped curve seen in typical children (30:00). The speaker discusses underlying mechanisms for these differences and notes that similar central neuronal abnormalities are relevant for chronic pain (31:00). Autistic participants also exhibited higher power at slow Delta and Theta and fast Beta bands (32:36). Enhanced Delta oscillations in autistic individuals were associated with lower pain sensitivity, indicating a correlation between specific EEG activity and pain perception in autism (33:30). 

Study 5: Pain-evoked potentials

The speaker defines evoked potential (EP) as “the change in cortical activity that occurs in response to an event of some kind (34:20). She outlines the basics of EP detection, highlighting the influence of stimulation intensity and perceived pain on EEG amplitude (35:40). To date, only two studies (all male) on pain EPs in autism have been published (37:00). Granovsky’s findings suggest a discrepancy between pain reports and the responses from pain detecting areas in autism and highlight the sex-related nature of responses in the cortical pain-detecting regions (38:15).

Study 6: Heart Rate Variability (HRV)

Heart Rate Variability (HRV) reflects the autonomic regulation of the cardiovascular system, which is regulated by the sympathetic and parasympathetic nervous systems (38:30). Granovsky and her team conducted one of the first studies on HRV and pain in autism. They found that autistic participants had higher pain thresholds and lower pain perception than neurotypical groups (40:00). They concluded that higher parasympathetic (PS) activity is associated with lower pain perception, suggesting the PS system plays a protective role in pain sensitivity. This relationship between HRV and pain sensitivity in autism suggests that HRV may help gauge the severity of autism symptoms and day-to-day difficulties (42:30). Granovsky asserts that future investigation should aim to evaluate the role of sex in autism pain neurobiology and to develop mechanism-based precision therapy approaches for pain and SOR in autism (43:00). 

Conclusion

The research discussed in this presentation highlights the intricate relationship between sensory processing, pain perception, and autism. Through a combination of quantitative and qualitative investigation, the presenters established a link between SMD and heightened pain sensitivity in autism, revealed distinct patterns in EEG and HRV activity related to pain in autism, and shed light on the physical and communication challenges related to pain experienced by autistic people every day (44:00). Bar-Shalita emphasizes the gap in awareness and communication around pain experiences in autism and reminds that common autistic behaviors may be a form of communicating pain (44:45). She provides thanks and acknowledgments (45:15) before the Q&A session (46:00).