Conjugate eye movements and gamma power modulation of the EEG in persistent vegetative state

Balazs, Susanne; Stepan, Christoph; Binder, Heinrich; Gizycki, Hans von; Avitable, M.; Obersteiner, Armin; Rattay, Frank; Selesnick, Ivan; Bódis-Wollner, Iván

doi:10.1016/j.jns.2006.02.007

Cited by 13 publications

(13 citation statements)

References 21 publications

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“…By taking into account that, first, the recovery of the functions of consciousness and the activation of precuneus are synchronous with the anatomofunctional restoration of long‐range corticocortical and/or corticothalamic connections [Laureys et al, ; Silva et al, ; Voss et al, ] and, second, the importance of slow oscillations as elements of long‐range connectivity [Sarnthein et al, ; von Stein and Sarnthein, ], we are led to speculate that the emergence and consolidation of coherent delta oscillations at mid‐parietal site of subjects who are coming out from VS reflect the progress of these same phenomena of reconnection. Moreover, despite the diversity of our approach to the problem, we can agree with Balazs et al and Hildebrandt et al , that the emergence from the VS is somehow characterized by the recovery of primary visual and/or visual associative areas (paravisual cortices) and probably deals with a regained (or better) awareness of the environment, perhaps in view of future interaction with it.…”

Section: Discussionsupporting

confidence: 79%

Cortical source of blink-related delta oscillations and their correlation with levels of consciousness

et al. 2012

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Recently, blink-related delta oscillations (delta BROs) have been observed in healthy subjects during spontaneous blinking at rest. Delta BROs have been linked with continuous gathering of information from the surrounding environment, which is classically attributed to the precuneus. Furthermore, fMRI studies have shown that precuneal activity is reduced or missing when consciousness is low or absent. We therefore hypothesized that the source of delta BROs in healthy subjects could be located in the precuneus and that delta BROs could be absent or reduced in patients with disorders of consciousness (DOC). To test these hypotheses, electroencephalographic (EEG) activity at rest was recorded in 12 healthy controls and nine patients with DOC (four vegetative states, and five minimally conscious states). Three-second-lasting EEG epochs centred on each blink instance were analyzed in both time- (BROs) and frequency domains (event-related spectral perturbation or ERSP and intertrial coherence or ITC). Cortical sources of the maximum blink-related delta power, corresponding to the positive peak of the delta BROs, were estimated by standardized Low Resolution Electromagnetic Tomography. In control subjects, as expected, the source of delta BROs was located in the precuneus, whereas in DOC patients, delta BROs were not recognizable and no precuneal localization was possible. Furthermore, we observed a direct relationship between spectral indexes and levels of cognitive functioning in all subjects participating in the study. This reinforces the hypothesis that delta BROs reflect neural processes linked with awareness of the self and of the environment.

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Section: Discussionsupporting

confidence: 79%

Cortical source of blink-related delta oscillations and their correlation with levels of consciousness

et al. 2012

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“…Such EEG properties are shared by many comatose and even minimally conscious state (MCS) patients. Gamma activity has been found to be present in all tested PVS patients [ 17 ], however, an increase of gamma power together with conjugate eye movements, a sign of voluntary movement in healthy subjects, was only seen in "less severe" cases [ 17 ]. To our knowledge, only one EEG study (quantitative electric tomography, QEEGt) detected specific activity changes in the EEG spectrum of an 8 year old PVS patient in response to his mothers voice [ 18 ].…”

Section: Introductionmentioning

confidence: 99%

Does any aspect of mind survive brain damage that typically leads to a persistent vegetative state? Ethical considerations

Panksepp

Fuchs

García

et al. 2007

Philos Ethics Humanit Med

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Recent neuroscientific evidence brings into question the conclusion that all aspects of consciousness are gone in patients who have descended into a persistent vegetative state (PVS). Here we summarize the evidence from human brain imaging as well as neurological damage in animals and humans suggesting that some form of consciousness can survive brain damage that commonly causes PVS. We also raise the issue that neuroscientific evidence indicates that raw emotional feelings (primary-process affects) can exist without any cognitive awareness of those feelings. Likewise, the basic brain mechanisms for thirst and hunger exist in brain regions typically not damaged by PVS. If affective feelings can exist without cognitive awareness of those feelings, then it is possible that the instinctual emotional actions and pain "reflexes" often exhibited by PVS patients may indicate some level of mentality remaining in PVS patients. Indeed, it is possible such raw affective feelings are intensified when PVS patients are removed from life-supports. They may still experience a variety of primary-process affective states that could constitute forms of suffering. If so, withdrawal of life-support may violate the principle of nonmaleficence and be tantamount to inflicting inadvertent "cruel and unusual punishment" on patients whose potential distress, during the process of dying, needs to be considered in ethical decision-making about how such individuals should be treated, especially when their lives are ended by termination of life-supports. Medical wisdom may dictate the use of more rapid pharmacological forms of euthanasia that minimize distress than the de facto euthanasia of life-support termination that may lead to excruciating feelings of pure thirst and other negative affective feelings in the absence of any reflective awareness.

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“…However, reliable measurement of saccades in response to memory or novel visual stimuli is difficult in DOC patients because many experimental paradigms require conscious awareness. There has been little research looking specifically at saccadic measures in DOC, except for quick saccadic oscillations (39). Microsaccades (small involuntary jerks of the eye) may be useful as an alternative for eye movement assessment of visual attention in the future (48–50), but their role in DOC, if any, have yet to be established.…”

Section: Reviewmentioning

confidence: 99%

Eye Movement Measurement in Diagnostic Assessment of Disorders of Consciousness

2014

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We review the literature to appraise the evidence supporting or disputing the use of eye movement measurement in disorders of consciousness (DOC) with low levels of arousal or awareness, such as minimally conscious state (MCS), vegetative state (VS), and coma for diagnostic and prognostic purposes. We will focus on the effectiveness of each technique in the diagnostic classification of these patients and the gradual trend in research from manual to computerized tracking methods. New tools have become available at clinicians’ disposal to assess eye movements with high spatial and temporal fidelity. The close relationship between eye movement generation and organic dysfunction in the brain allows these tools to be applied to the assessment of severe DOC as a unique supplementary toolset. We posit that eye tracking can improve clinical diagnostic precision for DOC, a key component of assessment that often dictates the course of clinical care in DOC patients. We see the emergence of long-term eye-tracking studies with seamless integration of technology in the future to improve the performance of clinical assessment in DOC.

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Conjugate eye movements and gamma power modulation of the EEG in persistent vegetative state

Cited by 13 publications

References 21 publications

Cortical source of blink-related delta oscillations and their correlation with levels of consciousness

Cortical source of blink-related delta oscillations and their correlation with levels of consciousness

Does any aspect of mind survive brain damage that typically leads to a persistent vegetative state? Ethical considerations

Eye Movement Measurement in Diagnostic Assessment of Disorders of Consciousness

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