Reconstructing Covert Consciousness: Neural Decoding as a Novel Consciousness Assessment.

Some patients with severe brain injury who appear unresponsive can still show covert consciousness by intentionally modulating their brain activity in response to commands, as detected by fMRI or EEG. However, current methods for detecting this covert consciousness have important limitations: they are not sensitive enough, rely on assumptions about brain function that may be incorrect, and fail to capture the full range of conscious experience. Neural decoding, a technique that reconstructs stimuli and concepts from brain activity, offers a promising new approach that could overcome these shortcomings. This article reviews the current state of covert consciousness assessments, their limitations, the science of neural decoding, and how it might be applied to disorders of consciousness, suggesting that neural decoding could improve sensitivity and better address what patients can actually experience.

Study at a glance

Abstract

Determining the level of consciousness in patients with brain injury-and more fundamentally, establishing what they can experience-is ethically and clinically impactful. Patient behaviors may unreliably reflect their level of consciousness: a subset of unresponsive patients demonstrate covert consciousness by willfully modulating their brain activity to commands through fMRI or EEG. However, current paradigms for assessing covert consciousness remain fundamentally limited because they are insensitive, rely on imperfect assumptions of functional neuroanatomy, and do not reflect the spectrum of conscious experience. Neural decoding, in which stimuli and concepts are reconstructed from brain activity, offers a novel approach to covert consciousness assessment that overcomes many of these limitations. In this article, we discuss the current state of covert consciousness assessments, their shortcomings, the state of the science in neural decoding, the potential application of neural decoding to disorders of consciousness, and future directions that may help realize this potential. To do so, we searched PubMed and Google Scholar databases for pertinent articles published between January 1990 and September 2024, using the search terms "covert consciousness," "cognitive motor dissociation," "neural decoding," and "semantic decoding." Redefining covert consciousness with neural decoding may improve sensitivity, enhance granularity, and more directly address the question of what patients can experience after brain injury.