You might want to consult the book referenced below, with one chapter reference Disintegrated experience: Dissociation and stress.
By Spiegel, David
Casey, Patricia R. (Ed); Strain, James J. (Ed). (2016). Trauma- and stressor-related disorders: A handbook for clinicians , (pp. 119-132). Arlington, VA, US: American Psychiatric Publishing, Inc., xx, 224 pp.
Psychiatrists and psychologists have been divided about dissociation since the earliest days of these professions. The pioneering psychologist Pierre Janet (1889) usefully described dissociation as desaggregation mentale, a means of managing emotional conflict by isolating memory, usually involving traumatic experience, from current cognition and affect. The findings described in this chapter are consistent with the notion that dissociative symptoms can interfere with the cognitive and affective processing thought to mediate the efficacy of psychotherapy for PTSD. As a whole, these studies make it clear that trauma and dissociation are linked, that dissociation reflects the way brains function in response to trauma, and that awareness of this distinct subtype enhances treatment response. (PsycINFO Database Record (c) 2016 APA, all rights reserved)
Outside stimuli such as triggers and cues can easily set off internal chaos or totally shut it out depending on the identity or part that was triggered. Sometimes a part can be heavily triggered and then another part will come take over and let the person doesn't know why they feel different or that anything triggered them. Dissociation is a great tool to be able to deal with the traumas these people face. Like another Part coming to protect them and avoid being destabilized. Are you asking about external calming stimuli helping internal chaos calm down?