This article reviews the nosological criteria and functional neuroanatomical basis for brain death, coma, vegetative state, minimally conscious state, and locked-in syndrome. Functional neuroimaging techniques, such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and electrophysiological methods, provide new insights into cerebral activity in patients with severe brain damage. These techniques can help identify residual brain function, but their use is methodologically complex and requires careful quantitative analysis and interpretation. Ethical frameworks for research in these patient populations need further development. Currently, clinical examinations remain the standard for accurate diagnosis and prognosis. Neuroimaging techniques are promising tools for clinical research, aiming to enhance our understanding of the underlying mechanisms of these disorders. The article also discusses the challenges and ethical considerations in using these techniques, emphasizing the importance of balancing research advancements with protections for vulnerable patient populations.This article reviews the nosological criteria and functional neuroanatomical basis for brain death, coma, vegetative state, minimally conscious state, and locked-in syndrome. Functional neuroimaging techniques, such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and electrophysiological methods, provide new insights into cerebral activity in patients with severe brain damage. These techniques can help identify residual brain function, but their use is methodologically complex and requires careful quantitative analysis and interpretation. Ethical frameworks for research in these patient populations need further development. Currently, clinical examinations remain the standard for accurate diagnosis and prognosis. Neuroimaging techniques are promising tools for clinical research, aiming to enhance our understanding of the underlying mechanisms of these disorders. The article also discusses the challenges and ethical considerations in using these techniques, emphasizing the importance of balancing research advancements with protections for vulnerable patient populations.