Electrophysiological evidence of preserved hearing at the end of life

Abstract

this study attempts to answer the question: "is hearing the last to go?" We present evidence of hearing among unresponsive actively dying hospice patients. Individual ERP (MMN, P3a, and P3b) responses to deviations in auditory patterns are reported for conscious young, healthy control participants, as well as for hospice patients, both when the latter were conscious, and again when they became unresponsive to their environment. Whereas the MMN (and perhaps too the P3a) is considered an automatic response to auditory irregularities, the P3b is associated with conscious detection of oddball targets. All control participants, and most responsive hospice patients, evidenced a "local" effect (either a MMN, a P3a, or both) and some a "global" effect (P3b) to deviations in tone, or deviations in auditory pattern. importantly, most unresponsive patients showed evidence of MMn responses to tone changes, and some showed a P3a or P3b response to either tone or pattern changes. Thus, their auditory systems were responding similarly to those of young, healthy controls just hours from end of life. Hearing may indeed be one of the last senses to lose function as humans die. In the last hours before an expected natural death many people enter a period of unresponsiveness, during which they no longer respond to their external environment. This can be a profound and spiritual time for families, but it is currently unknown whether unresponsive patients are aware of the touch or words of their loved ones. There is a persistent belief, however, that some unresponsive patients may still be aware of touch and sound 1 , despite being unable to reliably signal their awareness. Much of this belief comes from reports of near-death experiences (NDEs), where a common recurring element of this experience is hearing unusual noises or hearing oneself pronounced dead 2-4. Reports from NDEs, however, are difficult to interpret, because incidence of NDEs is low, between 6% 5 and 12% 6 of cardiac arrest survivors, and the cognitive neuroscience underlying NDEs remains hotly debated 7-9 and poorly understood 10-12. Further perpetuating the belief that "hearing is the last to go" are some family members and health care providers who have reported that unresponsive patients will occasionally groan or make a small facial movement in response to hearing a familiar voice, but to our knowledge there is no empirical evidence to corroborate these anecdotes 13. is it possible for a dying brain to sustain awareness? Neuroprotective mechanisms, mainly the blood-brain barrier, reduce neuronal firing in response to ischemia (a common physiological cause of unresponsiveness at the end of life), which could protect the brain from irreversible brain damage under these conditions 14. The brain's tolerance to ischemia has been demonstrated in autopsy, as only about 60% of patients who had been declared brain dead before death showed signs of moderate to severe cortical ischemia, and only about 30% in deep brain structures such as the thalamus and basal ganglia, and a...

The death of Gregory Bateson, or why linguists should study language at the end of life

“…The durability of turn-taking suggests that it is accurate to characterize language as a layering of overlapping layers of abilities, which raises the further question that they may be lost somewhat in the order that they were acquired (a la Jakobson's regression hypothesis; on which, see below). There is a folk notion that for dying people "hearing is the last sense to go," which seems to have been confirmed with recent EEG studies (Blundon et al, 2020). However, the only way for this to be verified absent brain monitoring equipment is if the dying person responds in a visible way.…”

“…The barrier of ethical approval may exist more people's minds than in actual practice; medical researchers in fact gain ethical approval for many studies that do not directly improve care for patients, including with the dying. A recent example is Blundon et al (2020), an EEG study of 13 dying patients' acoustic processing abilities in order to gain insight into the amount of awareness that dying people have. Ethics approval for this study came from the University of British Columbia Behavioral Research Ethics Board.…”

Intercountry and intracountry variations in opinions of palliative care specialist physicians in Germany, Italy, Japan and UK about continuous use of sedatives: an international cross-sectional survey

“…Approaches such as Bispectral Index monitoring are in the early stages of evaluation as measures to monitor sedative effects in palliative care patients 42 43. Other research approaches may include the use of functional MRI, which has also been used to assess awareness in patients in vegetative or minimally conscious states 44–46. More research is needed to understand real patient experience, including the degree of distress in patients with reduced consciousness.…”

Sounds of Etruria: aural characteristics of the Tomba dell'Orco, Tarquinia

“…Before death, audition is the last human sense to survive (Blundon et al 2020). Sound consequently provides a final perceptual boundary between life and death.…”