Bjørn Erik Juel

• Albantakis, Larissa; Barbosa, Leonardo; Findlay, Graham; Grasso, Matteo; Haun, Andrew M. & Marshall, William [Vis alle 16 forfattere av denne artikkelen] (2023). Integrated information theory (IIT) 4.0: Formulating the properties of phenomenal existence in physical terms. PLoS Computational Biology. ISSN 1553-734X. 19(10). doi: 10.1371/journal.pcbi.1011465. Fulltekst i vitenarkiv
• Aamodt, Arnfinn; Nilsen, Andre Sevenius; Markhus, Rune; Kusztor, Aniko; Hasanzadehmoghadam, Fatemeh & Kauppi, Nils [Vis alle 9 forfattere av denne artikkelen] (2023). EEG Lempel-Ziv complexity varies with sleep stage, but does not seem to track dream experience. Frontiers in Human Neuroscience. ISSN 1662-5161. 16, s. 1–19. doi: 10.3389/fnhum.2022.987714. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Thürer, Benjamin; Aamodt, Arnfinn & Storm, Johan Frederik (2022). Are we really unconscious in “unconscious” states? Common assumptions revisited. Frontiers in Human Neuroscience. ISSN 1662-5161. 16. doi: 10.3389/fnhum.2022.987051. Fulltekst i vitenarkiv
• Arena, Alessandro; Juel, Bjørn Erik; Comolatti, Renzo; Thon, Sarah & Storm, Johan Frederik (2022). Capacity for consciousness under ketamine anaesthesia is selectively associated with activity in posteromedial cortex in rats. Neuroscience of Consciousness. ISSN 2057-2107. 2022(1), s. 1–15. doi: 10.1093/nc/niac004. Fulltekst i vitenarkiv Vis sammendrag

  It remains unclear how specific cortical regions contribute to the brain’s overall capacity for consciousness. Clarifying this could help distinguish between theories of consciousness. Here, we investigate the association between markers of regionally specific (de)activation and the brain’s overall capacity for consciousness. We recorded electroencephalographic responses to cortical electrical stimulation in six rats and computed Perturbational Complexity Index state-transition (PCIST), which has been extensively validated as an index of the capacity for consciousness in humans. We also estimated the balance between activation and inhibition of specific cortical areas with the ratio between high and low frequency power from spontaneous electroencephalographic activity at each electrode. We repeated these measurements during wakefulness, and during two levels of ketamine anaesthesia: with the minimal dose needed to induce behavioural unresponsiveness and twice this dose. We found that PCIST was only slightly reduced from wakefulness to light ketamine anaesthesia, but dropped significantly with deeper anaesthesia. The high-dose effect was selectively associated with reduced high frequency/low frequency ratio in the posteromedial cortex, which strongly correlated with PCIST. Conversely, behavioural unresponsiveness induced by light ketamine anaesthesia was associated with similar spectral changes in frontal, but not posterior cortical regions. Thus, activity in the posteromedial cortex correlates with the capacity for consciousness, as assessed by PCIST, during different depths of ketamine anaesthesia, in rats, independently of behaviour. These results are discussed in relation to different theories of consciousness.

• Arena, Alessandro; Juel, Bjørn Erik; Comolatti, Renzo; Thon, Sarah Kriebel & Storm, Johan (2021). Does the posteromedial cortex play a primary role for the capacity for consciousness in rats? bioRxiv. ISSN 2692-8205. doi: 10.1101/2021.01.22.427747. Vis sammendrag

  It remains unclear how specific cortical regions contribute to the brain’s overall capacity for consciousness. Clarifying this could help distinguish between theories of consciousness. Here, we investigate the association between markers of regionally specific (de)activation and the brain’s overall capacity for consciousness. We recorded electroencephalographic (EEG) responses to cortical electrical stimulation in 6 rats, and computed Perturbational Complexity Index state-transition (PCIST), which has been extensively validated as an index of the capacity for consciousness in humans. We also estimated the balance between activation and inhibition of specific cortical areas with the ratio between high and low frequency power (HF/LF) from spontaneous EEG activity at each electrode. We repeated these measurements during wakefulness, and under the influence of ketamine anaesthesia at two doses: the minimal dose needed to induce behavioural unresponsiveness and twice this dose. We found that PCIST was only slightly reduced from wakefulness to light ketamine anaesthesia, but dropped significantly down with deeper anaesthesia. The high-dose effect was selectively associated with reduced HF/LF ratio in the posteromedial cortex, which strongly correlated with PCIST. Conversely, behavioural unresponsiveness induced by light ketamine anaesthesia, was associated with similar spectral changes in frontal, but not posterior cortical regions. These findings seem to support the claim that the posteromedial cortex may play a primary role for the capacity for consciousness. Such region-specific associations between cortical activation and the overall capacity for consciousness must be accounted for by theories of consciousness.

• Aamodt, Arnfinn; Nilsen, Andre Sevenius; Thürer, Benjamin; Moghadam, Fatemeh Hasanzadeh; Kauppi, Nils & Juel, Bjørn Erik [Vis alle 7 forfattere av denne artikkelen] (2021). EEG Signal Diversity Varies With Sleep Stage and Aspects of Dream Experience. Frontiers in Psychology. ISSN 1664-1078. 12. doi: 10.3389/fpsyg.2021.655884. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Thürer, Benjamin & Storm, Johan Frederik (2020). Proposed EEG measures of consciousness: asystematic, comparative review. PsyArXiv. doi: 10.31234/osf.io/sjm4a.
• Halder, Sebastian; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Raghavan, L Venkat & Storm, Johan Frederik (2020). Changes in measures of consciousness during anaesthesia of one hemisphere (Wada test). NeuroImage. ISSN 1053-8119. 226. doi: 10.1016/j.neuroimage.2020.117566. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Farnes, Nadine; Romundstad, Luis Georg & Storm, Johan Frederik (2020). Behavioral effects of sub-anesthetic ketamine in a go/no-go task. Journal of Psychedelic Studies. ISSN 2559-9283. 4(3), s. 156–162. doi: 10.1556/2054.2020.00126. Fulltekst i vitenarkiv
• Juel, Bjørn Erik; Romundstad, Luis Georg; Storm, Johan Frederik & Larsson, Pål Gunnar (2020). Validation of a new approach for distinguishing anesthetized from awake state in patients using directed transfer function applied to raw EEG. Journal of clinical monitoring and computing. ISSN 1387-1307. s. 1–14. doi: 10.1007/s10877-020-00603-x. Fulltekst i vitenarkiv Vis sammendrag

  We test whether a measure based on the directed transfer function (DTF) calculated from short segments of electroencephalography (EEG) time-series can be used to monitor the state of the patients also during sevoflurane anesthesia as it can for patients undergoing propofol anesthesia. We collected and analyzed 25-channel EEG from 7 patients (3 females, ages 41–56 years) undergoing surgical anesthesia with sevoflurane, and quantified the sensor space directed connectivity for every 1-s epoch using DTF. The resulting connectivity parameters were compared to corresponding parameters from our previous study (n = 8, patients anesthetized with propofol and remifentanil, but otherwise using a similar protocol). Statistical comparisons between and within studies were done using permutation statistics, a data driven algorithm based on the DTF-parameters was employed to classify the epochs as coming from awake or anesthetized state. According to results of the permutation tests, DTF-parameter topographies were significantly different between the awake and anesthesia state at the group level. However, the topographies were not significantly different when comparing results computed from sevoflurane and propofol data, neither in the awake nor in anesthetized state. Optimizing the algorithm for simultaneously having high sensitivity and specificity in classification yielded an accuracy of 95.1% (SE = 0.96%), with sensitivity of 98.4% (SE = 0.80%) and specificity of 94.8% (SE = 0.10%). These findings indicate that the DTF changes in a similar manner when humans undergo general anesthesia caused by two distinct anesthetic agents with different molecular mechanisms of action.

• Farnes, Nadine; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Romundstad, Luis Georg & Storm, Johan Frederik (2020). Increased signal diversity/complexity of spontaneous EEG, but not evoked EEG responses, in ketamine-induced psychedelic state in humans. PLOS ONE. ISSN 1932-6203. 15:e024056(11), s. 1–21. doi: 10.1371/journal.pone.0242056. Fulltekst i vitenarkiv Vis sammendrag

  Objective How and to what extent electrical brain activity is affected in pharmacologically altered states of consciousness, where it is mainly the phenomenological content rather than the level of consciousness that is altered, is not well understood. An example is the moderately psychedelic state caused by low doses of ketamine. Therefore, we investigated whether and how measures of evoked and spontaneous electroencephalographic (EEG) signal diversity are altered by sub-anaesthetic levels of ketamine compared to normal wakefulness, and how these measures relate to subjective assessments of consciousness. Methods High-density electroencephalography (EEG, 62 channels) was used to record spontaneous brain activity and responses evoked by transcranial magnetic stimulation (TMS) in 10 healthy volunteers before and after administration of sub-anaesthetic doses of ketamine in an open-label within-subject design. Evoked signal diversity was assessed using the perturbational complexity index (PCI), calculated from the global EEG responses to local TMS perturbations. Signal diversity of spontaneous EEG, with eyes open and eyes closed, was assessed by Lempel Ziv complexity (LZc), amplitude coalition entropy (ACE), and synchrony coalition entropy (SCE). Results Although no significant difference was found in the index of TMS-evoked complexity (PCI) between the sub-anaesthetic ketamine condition and normal wakefulness, all the three measures of spontaneous EEG signal diversity showed significantly increased values in the sub-anaesthetic ketamine condition. This increase in signal diversity also correlated with subjective assessment of altered states of consciousness. Moreover, spontaneous signal diversity was significantly higher when participants had eyes open compared to eyes closed, both during normal wakefulness and during influence of sub-anaesthetic ketamine doses. Conclusion The results suggest that PCI and spontaneous signal diversity may be complementary and potentially measure different aspects of consciousness. Thus, our results seem compatible with PCI being indicative of the brain’s ability to sustain consciousness, as indicated by previous research, while it is possible that spontaneous EEG signal diversity may be indicative of the complexity of conscious content. The observed sensitivity of the latter measures to visual input seems to support such an interpretation. Thus, sub-anaesthetic ketamine may increase the complexity of both the conscious content (experience) and the brain activity underlying it, while the level, degree, or general capacity of consciousness remains largely unaffected.

• Juel, Bjørn Erik; Comolatti, Renzo; Albantakis, Larissa & Tononi, Giulio (2019). When is an action caused from within? Quantifying the causal chain leading to actions in simulated agents. ALIFE : Proceedings of the Artificial Life Conference. ISSN 2693-1508. doi: 10.1162/isal_a_00207. Fulltekst i vitenarkiv
• Nilsen, Andre Sevenius; Juel, Bjørn Erik & Marshall, William (2019). Evaluating approximations and heuristic measures of integrated information. Entropy. ISSN 1099-4300. 21(5), s. 1–23. doi: 10.3390/e21050525. Fulltekst i vitenarkiv
• Kusztor, Aniko; Raud, Liisa; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Storm, Johan Frederik & Huster, Rene (2019). Sleep deprivation differentially affects subcomponents of cognitive control . Sleep. ISSN 0161-8105. 42(4). doi: 10.1093/sleep/zsz016.
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2018). Distinguishing anesthetized from awake state in patients: A new approach using one second segments of raw EEG. Frontiers in Human Neuroscience. ISSN 1662-5161. 12:40, s. 1–14. doi: 10.3389/fnhum.2018.00040. Fulltekst i vitenarkiv

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• Murphy, Ricardo; Nilsen, Andre Sevenius; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2019). A multiarea Hill-Tononi thalamocortical network model evaluated with proposed measures of consciousness.
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Marshall, William & Storm, Johan Frederik (2019). Estimating Integrated Information: How noise, sampling, and perturbations affect Phi.
• Murphy, Ricardo; Nilsen, Andre Sevenius; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2018). Implementation of the Hill-Tononi thalamocortical network model in the neural simulator NEST.
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2018). Changes in EEG captured by Directed Transfer Function is sufficient to accurately classify the state of wakefulness in patients undergoing sevoflurane anesthesia in accordance with the clinician’s judgement .
• Juel, Bjørn Erik; Nilsen, Andre Sevenius; Murphy, Ricardo & Storm, Johan Frederik (2018). Thalamocortical model for studying the effects of neuromodulation on network properties .
• Juel, Bjørn Erik; Nilsen, Andre Sevenius; Gosseries, Olivia; Sarasso, Simone; Larsson, Pål Gunnar & Boly, Malanie [Vis alle 9 forfattere av denne artikkelen] (2018). Measures of connectivity, complexity and signal diversity in EEG distinguish conscious from unconscious state during anesthesia.
• Nilsen, Andre Sevenius; Juel, Bjørn Erik & Storm, Johan Frederik (2018). Attentional Modulation on Measures of Conscious States.
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Marshall, William & Storm, Johan Frederik (2018). Calculating conscious capacity: approximations, analogues, and correlates of PHI.
• Halder, Sebastian; Venkat Raghavan, L; Juel, Bjørn Erik; Nilsen, Andre Sevenius & Storm, Johan Frederik (2018). Effects of intracarotid sodium amobarbital procedure (ISAP) on cortical complexity.
• Farnes, Nadine; Juel, Bjørn Erik; Nilsen, Andre Sevenius; Romundstad, Luis Georg; Larsson, Pål Gunnar & Engstrøm, Morten [Vis alle 7 forfattere av denne artikkelen] (2017). Integrated information in sub-anaesthetic ketamine measured by TMS and EEG.
• Bremnes, Thomas Rene; Juel, Bjørn Erik; Sarasso, Simone; Boly, Melanie; Casarotto, Silvia & Casali, Adenauer G. [Vis alle 12 forfattere av denne artikkelen] (2017). Unresponsive states with and without report of conscious experience show distinct patterns of EEG-based effective brain connectivity in humans.
• Nilsen, Andre Sevenius; Arena, Alessandro; Juel, Bjørn Erik; Storm, Johan Frederik; Murphy, Ricardo & Hu, Hua [Vis alle 7 forfattere av denne artikkelen] (2017). Forsknigstorget: Hvordan kan hjernen skape bevissthet.
• Juel, Bjørn Erik; Bremnes, Thomas Rene; Larsson, Pål Gunnar & Storm, Johan Frederik (2017). Classifying states of (un)consciousness based on one second of raw EEG.
• Juel, Bjørn Erik; Kusztor, Aniko; Nilsen, Andre Sevenius; Farnes, Nadine; Larsson, Pål Gunnar & Romundstad, Luis Georg [Vis alle 7 forfattere av denne artikkelen] (2017). Changes in electrophysiological markers of consciousness in response to various anesthetics.
• Nilsen, Andre Sevenius; Storm, Johan Frederik & Juel, Bjørn Erik (2017). Attentional Modulation on Measures of Conscious States.
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Storm, Johan Frederik; Romundstad, Luis Georg & Larsson, Pål Gunnar (2017). Markers of consciousness before, during, and after anesthesia .
• Nilsen, Andre Sevenius; Juel, Bjørn Erik; Storm, Johan Frederik; Murphy, Ricardo; Plesser, Hans Ekkehard & Hill, Sean [Vis alle 8 forfattere av denne artikkelen] (2017). Implementation of the Hill-Tononi thalamocortical network model in the neural simulator NEST .
• Juel, Bjørn Erik; Nilsen, Andre Sevenius; Farnes, Nadine & Storm, Johan Frederik (2017). Comparing electrophysiological markers of consciousness between physiologically distinct states of wakefulness.
• Nilsen, Andre Sevenius; Juel, Bjørn Erik & Storm, Johan Frederik (2017). Proxies for integrated information of microscale networks Is it possible to predict PHI? .
• Murphy, Ricardo; Nilsen, Andre Sevenius; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2017). Implementation of the Hill-Tononi thalamocortical network model in the neural simulator NEST.
• Nilsen, Andre Sevenius; Murphy, Ricardo; Juel, Bjørn Erik; Plesser, Hans Ekkehard; Hill, Sean & Nieus, Thierry [Vis alle 8 forfattere av denne artikkelen] (2017). Simulating deep sleep and awake states in a mammalian thalamocortical model.
• Juel, Bjørn Erik; Bremnes, Thomas Rene; Larsson, Pål Gunnar & Storm, Johan Frederik (2016). Comparing Potential Objective Measures of Human Consciousness: the Perturbational Complexity Index and the Directed Transfer Function.
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2016). Differences in effective connectivity can be used to separate conscious from unconscious states in patients undergoing general anesthesia.
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2015). Can We Monitor Consciousness in Real Time with EEG?
• Juel, Bjørn Erik; Romundstad, Luis Georg; Kolstad, Frode; Storm, Johan Frederik & Larsson, Pål Gunnar (2015). Monitoring Brain Connectivity to Predict Patients’ Level of Awareness.

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