The Neuroethics of Disorders of Consciousness

A Brief History of Evolving Ideas

Michael J. Young; Yelena G. Bodien; Joseph T. Giacino; Joseph J. Fins; Robert D. Truog; Leigh R. Hochberg; Brian L. Edlow


Brain. 2021;144(11):3291-3310. 

In This Article

Philosophical Framing

From outside in, the limits of consciousness, the boundaries defining its presence or absence, are notoriously fuzzy. This is both due to the nature of the behavioural methods traditionally used to detect consciousness and the ill-defined and fluctuating nature of consciousness itself. With the exception of the first-person case, wherein one may directly access one's own inner thoughts and mental states, historically consciousness was recognized as only inferable by the appearance and behaviours of others.[36,37] This inferential gap between perceptions of behaviours and ascription of conscious states to others has given rise to numerous philosophical puzzles around 'the problem of other minds'. Contemporary inquiry in philosophy of mind distinguishes between approaches to knowing whether or not another being is conscious and approaches surrounding knowing what the content of that consciousness may be. As we will later turn to, a rapidly evolving set of neuroimaging and electrophysiological techniques may provide tools to augment our ability to detect consciousness with greater precision, especially in borderline cases. These techniques are focused primarily on determining the presence or absence of consciousness in settings of uncertainty. One exception to this is the field of implanted brain–computer interfaces, where there is potential to enable rich efferent communication by people otherwise completely locked-in.[38] These same technologies may, in the future, similarly be used diagnostically, as the restoration of reliable and verifiable communication would remove any lingering question about an individual's consciousness.[39] While these technologies remain imperfect and cannot replace behavioural measures, their ability to detect consciousness missed by behavioural measures challenges longstanding historical and categorical reliance on behavioural measures in the ascription of conscious states, both in clinical practice and in philosophical tradition. Similarly, emerging neurotechnologies and methods of data analysis, particularly when they suggest a level of consciousness that exceeds that detected by behavioural measures, create an important research and clinical dilemma for which explicit guidance would be beneficial to clinicians, researchers, families and ultimately, patients. Pragmatic integration of philosophical insights with clinical categories can aid in grounding perspectives and informing taxonomy.