Are There Islands of Awareness?

Awareness may persist in fully disconnected cortical islands.We identify both natural and artificial examples of potential islands of awareness.Detecting islands of awareness poses difficult but often addressable challenges.The possibility of islands of awareness raises important ethical and legal issues.The discovery of islands of awareness would have important implications for debates about the nature of consciousness. Ordinary human experience is embedded in a web of causal relations that link the brain to the body and the wider environment. However, there might be conditions in which brain activity supports consciousness even when that activity is fully causally isolated from the body and its environment. Such cases would involve what we call islands of awareness: conscious states that are neither shaped by sensory input nor able to be expressed by motor output. This Opinion paper considers conditions in which such islands might occur, including ex cranio brains, hemispherotomy, and in cerebral organoids. We examine possible methods for detecting islands of awareness, and consider their implications for ethics and for the nature of consciousness. Ordinary human experience is embedded in a web of causal relations that link the brain to the body and the wider environment. However, there might be conditions in which brain activity supports consciousness even when that activity is fully causally isolated from the body and its environment. Such cases would involve what we call islands of awareness: conscious states that are neither shaped by sensory input nor able to be expressed by motor output. This Opinion paper considers conditions in which such islands might occur, including ex cranio brains, hemispherotomy, and in cerebral organoids. We examine possible methods for detecting islands of awareness, and consider their implications for ethics and for the nature of consciousness. Consciousness is first and foremost a property of living organisms – organisms that are embodied and embedded in environments. The contents of consciousness are shaped by the sensory stimuli received by the brain, and those contents in turn give rise to behaviours that prompt us to attribute consciousness to an organism. However, there are conscious states in which the transfer of information between the world and the brain is massively reduced, with the result that the brain (or parts thereof) becomes disconnected from its environment. In some conditions, disconnection is partial, so that some form of either input and/or output is retained. In other conditions, the disconnection is complete, so that the brain (or parts thereof) becomes fully isolated from its environment. What happens to consciousness when the brain becomes disconnected from its environment? Can it support islands of awareness (see Glossary), or does consciousness require the presence of (high bandwidth?) interaction between the brain and its environment? This question has long fascinated philosophers, but recent developments in neuroscience, neurosurgery, and neuroengineering now extend the scope of this discussion beyond the philosopher’s armchair and out into the laboratory and clinic. We address three issues raised by the possibility of islands of awareness. The first concerns their nature and distribution. Under what conditions might such islands arise? What forms might they take? How common might they be? A second issue concerns the detection of islands of awareness. Might current methods for detecting consciousness be applicable to islands of awareness, or will we need new tools for identifying consciousness in disconnected brains? A third issue concerns the implications of islands of awareness. What ethical implications might such islands have, and what might they tell us about the nature of consciousness? We address these issues by considering three conditions in which islands of awareness might be thought to occur: ex cranio brains; the neurosurgical procedure of hemispherotomy; and cerebral organoids. Although these three cases are by no means the only cases that could be considered here – for example, one might also consider whether islands of awareness could occur in utero 1Lagercrantz H. Changeux J.P. The emergence of human consciousness: from fetal to neonatal life.Pediatr. Res. 2009; 65: 255-260Crossref PubMed Scopus (116) Google Scholar – we focus on them here because they highlight the issues raised by islands of awareness with particular force and urgency. Before we turn to genuine islands of awareness, we begin with cases of merely partial disconnection. Clinical neurology offers a rich repertoire of cases to consider here, for structural lesions can cause the brain to become disconnected on either the input or the output side without loss of consciousness. Starting from the input side, we know that consciousness can be preserved in the absence of afferent activity from peripheral receptors and nerves. For example, acquired blindness is a condition in which patients lose sight but retain the capacity for imagery, visual dreaming, and vivid hallucination 2Menon G.J. et al.Complex visual hallucinations in the visually impaired: the Charles Bonnet Syndrome.Surv. 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