Reproduced from Laureys (2005) with permission It is noteworthy that the relationship between arousal and consciousness is not a simple linear one, i.e., increases in arousal do not necessarily equate to increased levels of consciousness. Studies with healthy individuals have shown how in some circumstances, increased arousal may cause a decrease in attention (Easterbrook, 1959; Cohen, 1993). Baker draws our attention to traumatic brain injury (TBI) patients experiencing post-traumatic amnesia, who may experience over-arousal (hyper-arousal), where an oversensitive filtering system may reject both relevant and irrelevant information relating to stimuli (2001). Whilst the relationship between arousal and awareness and attention with DOC has not yet been fully established, it is likely there are optimal relationships between the components which may be influenced by internal and external stimuli, or the lack thereof. This will be discussed further on in relation to sensory stimulation programmes with DOC. 2.5.5 Awareness Arousal is considered as the essential pre-requisite for the second condition, awareness, has been related to the contents of consciousness (Giacino & Whyte, 2005). Awareness has been described as comprising all subjective perceptions, feelings and thoughts (Posner, 2008). It is considered by mainstream neuroscience as dependent upon the functional capacity of the cerebral cortex to facilitate perceptual experiences (e.g., perceiving colours), bodily sensations in response to stimuli, moods (e.g., tiredness, boredom) and phenomenal aspects with emotional reactions akin to 'self-awareness’ such as regret or joy (Demertzi et al., 2009; Haugeland, 1985; Majerus et al., 2005). However, there exists some debate as to the relationship between awareness, self-awareness and consciousness, as the following section details. 2.5.6 Awareness or Consciousness? Providing a consensus definition of awareness is challenging, due to its synonymous use with which also lacks consensus definition in the literature (Aspen ‘consciousness’, Neurobehavioral Conference Workgroup, 1996). Moreover, a debate focuses on whether one takes the view that to hear, see and feel, or otherwise experience something, denotes consciousness, or if a more sophisticated self-awareness of these sensations is necessary. Some authors suggest there is separation between the concepts of awareness and consciousness. For example Tulving (1993) proposed consciousness as referring to the
Reproduced from Laureys (2005) with permission It is noteworthy that the relationship between arousal and consciousness is not a simple linear one, i.e., increases in arousal do not necessarily equate to increased levels of consciousness. Studies with healthy individuals have shown how in some circumstances, increased arousal may cause a decrease in attention (Easterbrook, 1959; Cohen, 1993). Baker draws our attention to traumatic brain injury (TBI) patients experiencing post-traumatic amnesia, who may experience over-arousal (hyper-arousal), where an oversensitive filtering system may reject both relevant and irrelevant information relating to stimuli (2001). Whilst the relationship between arousal and awareness and attention with DOC has not yet been fully established, it is likely there are optimal relationships between the components which may be influenced by internal and external stimuli, or the lack thereof. This will be discussed further on in relation to sensory stimulation programmes with DOC. 2.5.5 Awareness Arousal is considered as the essential pre-requisite for the second condition, awareness, has been related to the contents of consciousness (Giacino & Whyte, 2005). Awareness has been described as comprising all subjective perceptions, feelings and thoughts (Posner, 2008). It is considered by mainstream neuroscience as dependent upon the functional capacity of the cerebral cortex to facilitate perceptual experiences (e.g., perceiving colours), bodily sensations in response to stimuli, moods (e.g., tiredness, boredom) and phenomenal aspects with emotional reactions akin to 'self-awareness’ such as regret or joy (Demertzi et al., 2009; Haugeland, 1985; Majerus et al., 2005). However, there exists some debate as to the relationship between awareness, self-awareness and consciousness, as the following section details. 2.5.6 Awareness or Consciousness? Providing a consensus definition of awareness is challenging, due to its synonymous use with ‘consciousness’, which also lacks consensus definition in the literature (Aspen Neurobehavioral Conference Workgroup, 1996). Moreover, a debate focuses on whether one takes the view that to hear, see and feel, or otherwise experience something, denotes consciousness, or if a more sophisticated self-awareness of these sensations is necessary. Some authors suggest there is separation between the concepts of awareness and consciousness. For example Tulving (1993) proposed consciousness as referring to the
OKelly_2014_MT_DOC_Final_Thesis_for_online.docx