UBC Theses and Dissertations
Measurement of awareness at the end of life Blundon, Elizabeth G.
Here I report evidence of awareness among unresponsive hospice patients at the end of life. Chapter 2 describes the neurotypical neural networks underlying some EEG measures used to assess awareness, particularly activations of different attention networks associated with the P3a and P3b event-related potential (ERP) sub-components of the P300 ERP. I found that the primary neural generators of the P3a were frontal regions associated with exogenous attention processes, such as the Ventral Attention (Corbetta & Shulman, 2002) and Saliency (Menon & Uddin, 2010) networks. The neural generators of the P3b, by contrast, were parietal regions associated with endogenous attention processes, such as the Dorsal Attention Network (Corbetta & Shulman, 2002), and regions often involved in detecting oddball targets (H. Kim, 2014). Chapter 3 reports evidence of auditory cortical processing (Näätänen et al., 2007) among all unresponsive patients, and attention orienting or context updating (Polich, 2007) among some unresponsive patients. Chapter 4 describes the spatio-temporal dynamics of attention networks reported in Chapter 2 among individual neurotypical control participants, and both responsive and unresponsive hospice patients. While these results are highly nuanced, some unresponsive patients showed some fronto-parietal connectivity, and may have engaged in motor imagery. Chapter 5 reports evidence of stimulus-independent cognition occurring in the default mode network (Buckner et al., 2008a; Christoff et al., 2016; Raichle et al., 2001; Smallwood et al., 2012) among unresponsive patients during a period of rest. Chapter 6 reports evidence of a decrease in alpha-band oscillation power in the posterio-parietal cortex in response to music among unresponsive patients. As such a decrease in alpha-band power is associated with orienting of attention, this implies that these patients may be paying attention to the music. The results of this research suggest that some unresponsive hospice patients at the end of life may be aware. These results lend credence to the belief that “hearing is the last to go”, and that loved ones at the bedside should be encouraged to interact with their dying relatives for as long as possible. Furthermore, attention to music could be a promising new biomarker of awareness that has potential for clinical adaptation.
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