Sensory Defensiveness

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Prevalence[edit]

Estimated to be 5-10 precent of the world according to Julia Wilbarger.

Possible survival benefit for sensory defensiveness[edit]

“Most people ignore minor stimuli of which our ancestors may have been more aware. These stimuli may have served as warning signals to induce protective behaviors. But people with sensory defensiveness remain keenly aware of many subtle stimuli — such as a clothing tag that feels like a spider crawling on their skin — some to the point of severe psychological and physical reaction, Wilbarger says.” (Researcher examines sensory disorders, Rebecca Quigley, News from UW-Madison, Nov. 3, 2010, available online at: https://news.wisc.edu/researcher-examines-sensory-disorders/.)

Studies by Wilbarger of sensory defensiveness in fibromyalgia[edit]

As compared to patients with rheumatoid arthritis, Wilbarger et al. found that fibromyalgia patients had significantly increased sensory sensitivities to the following types of stimuli: tactile, auditory, olfactory (smell) and taste. The authors concluded that their fibromyalgia group had “hypersensitivities across multiple modalities. …Reports of increased aversion to non-noxious sensory stimuli across modalities is supportive of a view of dysregulation of central nervous system mechanisms that modulate aversive responses to sensation in people with FM.1 (Multisensory Hypersensitivity in Women With Fibromyalgia: Implications for Well Being and Intervention. Julia L. Wilbarger, PhD and Dane B. Cook, PhD, Arch Phys Med Rehabil. 2011 Apr; 92(4): 653–656. doi: 10.1016/j.apmr.2010.10.029, available in full online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3272297/.)

Wilbarger says that “someone who is oversensitive to one type of stimulus will probably be oversensitive to many others…” (Cited in Quigley. 2010) She went on to say: “I saw problems with children just managing their daily lives,” she says, explaining that she began recognizing the sensory-processing issues underlying those problems.

Risk in internationally adopted children[edit]

Wilbarger stated: “We found that internationally adopted children who spent more time in an institution or orphanage had more sensory processing problems compared with non-adopted children and internationally adopted children who either spent a brief time in institutions or were in foster care…” (Cited in Quigley. 2010)

Tools used by Wilbarger to investigate sensory defensiveness[edit]

Sensory challenge (involving Lucy Miller, director of the Sensory Processing Disorder Foundation). In it, the physiological responses are recorded from subjects to various sensations which were selected based on observation by parents of what most bothered the children. “For example, she chose the feather as a tactile stimulus because people with high sensitivity disorder had statistically larger physical responses to it than people with low sensitivity.” Wilbarger monitors HR and muscles of facial expression using sensors attached to the fingers, forehead and cheeks. She monitors for “physical and emotional reactions to auditory, olfactory and tactile stimuli — a crying baby, a cricket, smelly socks, vanilla, a feather and a small brush.”

Brainstem and grey matter cortical abnormalities in[edit]

An MRI study by Fallon et. al. (2013) found that fibromyalgia patients have shape abnormalities in the medulla. “Voxel-based morphometry analysis revealed that patients also demonstrated decreased local grey matter volumes in the brainstem (pons) and left precuneus, and increased grey matter volumes in bilateral primary somatosensory cortices.” The authors concluded that their findings “may be due to structure-related deficiencies in regions subserving descending nociceptive control”. (Structural alterations in brainstem of fibromyalgia syndrome patients correlate with sensitivity to mechanical pressure. Fallon N1, Alghamdi J, Chiu Y, Sluming V, Nurmikko T, Stancak A. Neuroimage Clin. 2013 Aug 9;3:163-70 available in full online at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3791285/. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Fibromyalgia, Role of the insula in[edit]

An fMRI study by Kim et al. of fibromyalgia patients looked for “variability in cerebral activation according to pain intensity and the association between variability in cerebral activation and clinical features”. Results showed that high pressure stimuli activated the insula on both sides of the brain more in fibromyalgia patients than controls. (Insular cortex is a trait marker for pain processing in fibromyalgia syndrome—blood oxygenation level-dependent functional magnetic resonance imaging study in Korea. Kim SH1, Chang Y, Kim JH, Song HJ, Seo J, Kim SH, Han SW, Nam EJ, Choi TY, Lee SJ, Kim SK. Clin Exp Rheumatol. 2011 Nov-Dec;29(6 Suppl 69):S19-27.)

An fMRI and electrocardiography study by Kim et al. was conducted on patients and health controls during rest and also during “sustained mechanical pressure-induced pain over the lower leg” which caused the patient to be in pain. “Functional connectivity associated with different S1 subregions was calculated, while S1(leg) connectivity (representation of the leg in the primary somatosensory cortex) was contrasted between the rest phase and the pain phase and was correlated with clinically relevant measures in FM.”

Results showed: “During the rest phase, FM patients showed decreased connectivity between multiple ipsilateral and cross-hemispheric S1 subregions, which was correlated with clinical pain severity. Compared to the rest phase, the pain phase produced increased S1(leg) connectivity to the bilateral anterior insula in FM patients, but not in healthy controls. Moreover, in FM patients, sustained pain-altered S1(leg) connectivity to the anterior insula was correlated with clinical/behavioral pain measures and autonomic responses.”

The authors concluded that “both somatic and nonsomatic dysfunction in FM, including clinical pain, pain catastrophizing, autonomic dysfunction, and amplified temporal summation, are closely linked with the degree to which evoked deep tissue pain alters S1 connectivity to salience/affective pain-processing regions. Additionally, diminished connectivity between S1 subregions during the rest phase in FM may result from ongoing widespread clinical pain.” (The somatosensory link in fibromyalgia: functional connectivity of the primary somatosensory cortex is altered by sustained pain and is associated with clinical/autonomic dysfunction. Kim J1, Loggia ML, Cahalan CM, Harris RE, Beissner F, Garcia RG, Kim H, Barbieri R, Wasan AD, Edwards RR, Napadow V. Arthritis Rheumatol. 2015 May;67(5):1395-405.)