By Rowena Kong
Many unfortunate and unresponsive patients might never be able to show a hint of perception of their loved-ones’ faithful support by the bedside or the sight of their tears behind hopeful smiles. As such, the very existence of these patients’ level of consciousness and the accuracy of their clinical behavioural assessments have been debatable. Medical authorities and experts have come up with the category of disorders of consciousness to include conditions that impair one’s state of awareness. “Minimally conscious state” and “persistent vegetative state” are two categorizations that have attracted particular interest due to the difficulty inherent in their identification and diagnosis (Bernat, 2006). In the case of patients in a minimally conscious state, there remains a certainty in their behavioural exhibition of sense of self and of the environment (Giacino et al., 2002). As for the persistent vegetative state, the condition is more severe and impacts one’s full range of behavioural responses to sensory stimuli in terms of their sustainability, reproducibility, purposefulness and voluntary nature (The Multi-Society Task Force on PVS, 1994). Of particular significance is the fact that the vegetative patient exhibits a total loss of awareness of the self and the environment while other autonomic bodily functions are still preserved at variable degree.
Casting a faint glimmer of hope on vegetative patients, Monti et al. (2010) managed to discover brain modulation activity in a certain few of these subjects in an fMRI study performed at centres in the United Kingdom and Belgium. When instructed by the experimenter to engage in motor and spatial imagery tasks, the brain scans of vegetative patients were comparable to those of healthy control individuals, highlighting concentration of activity on regions of the supplementary motor area and parahippocampal gyrus because of their respective associations with such imagery tasks. The results raise the question of vegetative patients’ capability of consciousness in the absence of corresponding behavioural evidence. Although only 5 out of 54 patients demonstrated such active modulation, the fact that the majority of the responsive group was diagnosed as being in a persistent vegetative state suggests that their telltale fMRI scans may be a slit of promise that could challenge current diagnostic criteria. Misdiagnosis is common with disorders of consciousness due to evaluators’ strong reliance on motor and behavioural assessments. This study enables us to peer deeper into potential residual brain functioning of vegetative state patients that hopefully bears connection with the non-physical side of consciousness that is still intact.
An additional component of the study involved an evaluation of the patients’ covert brain responses in complying with instructions to mentally engage in motor and spatial imagery tasks specified by the experimenter’s verbal descriptions of playing tennis and navigating familiar city streets, and then visually playing out each action or scene. This second part of the study was a communication task during which, once subjects had presumably been accustomed to earlier brain response activity for imagery tasks, they were instructed to perform the modulation process once again to represent their answers to yes-or-no questions related to themselves at this later stage. Should their choice of answer be positive, subjects were told to engage in either motor or spatial visualization, while a negative answer would require activation of the other type of visualization. And answer they did, with verified accuracy. Scans of brain activation patterns during prior imagery tasks corresponded with those of the communication task that were associated with the right answer.
Critics of the method of this study have contested that words like “tennis” and “house” used in the imagery instructions may have aroused unconscious automatic neural responses (Greenberg, 2007; Nachev & Husain, 2007; Owen et al., 2007). To clarify, the authors affirmed that the subjects’ responses were sustained for as long as they were instructed to be. This therefore strengthens the evidence that they were consciously engaged in such mental activity willfully. Another point of evidence mentioned was that the wording used did not activate brain regions that are normally associated with word processing, which would otherwise support the involvement of unconscious automatic responses. Rather, the activated areas were distinctly related to movements and spatial navigation.
Although it is too early to definitely conclude that vegetative patients are capable of consciousness (and, if so, to what degree), we are still rewarded with an insightful understanding of the potential residual workings of the brain when overt motor and behavioural abilities are severely compromised. Thus, the inadequacy of behavioural assessments and the definition of “minimal” consciousness should be subject to further discussion. This study’s findings also shed light on a possible latent side of our consciousness, one that is completely detached from physical channels of expression and response. Whether the patients in the above study exhibited a response that is primitive in a series of cognitive processes necessary for an end product of consciousness, or rather an extreme feat under the most debilitating constraints remains to be demystified. Furthermore, by using verbal questions to elicit silent responses from subjects, this study opens up new possibilities for research involving alternate sensory modalities, such as visual images or stimuli for those who are capable of eye movements.
Bernat, J. L. (2006). Chronic disorders of consciousness. The Lancet, 9517, 1181-1192.
Giacino, J. T., Ashwal, S., Childs, N., Cranford, R., Jennett, B., Katz, D. I.,…Zasler, N. D. (2002). The minimally conscious state. Neurology, 58, 349–353.
Greenberg, D. L. (2007). Comment on “Detecting Awareness in the Vegetative State”. Science, 315, 1221.
Monti, M. M., Vanhaudenhuyse, A., Coleman, M. R., Boly, M., Pickard, J. D., Tshibanda, L.,…Laureys, S. (2010). Willful modulation of brain activity in disorders of consciousness. The New England Journal of Medicine, 362, 579-589.
Nachev, P., & Husain, M. (2007). Comment on “Detecting Awareness in the Vegetative State”. Science, 315, 1221.
Owen, A.M., Coleman, M. R., Boly, M., Davis, M. H., Laureys, S., Jolles, D., & Pickard, J. D. (2007). Response to comments on “Detecting Awareness in the Vegetative State”. Science, 315, 1221.
The Multi-Society Task Force on PVS. (1994). Medical aspects of the persistent vegetative state. The New England Journal of Medicine,330, 1499-1508.
About the author:
Rowena Kong is a fourth year Psychology major who is interested in writing about a diverse range of topics. The brain’s mirror neurons and dopaminergic reward system fascinate her just as much as cultural universals and implicit social communication. During her spare time, she enjoys photography, fanfiction, and working with Photoshop to improve her amateurish skills.