@article{MTMT:1611469, title = {Complex Propagation Patterns Characterize Human Cortical Activity during Slow-Wave Sleep}, url = {https://m2.mtmt.hu/api/publication/1611469}, author = {Hangya, Balázs and Tihanyi, Benedek and Entz, László and Fabó, Dániel and Erőss, Loránd and Wittner, Lucia and Jakus, R and Varga, Viktor and Freund, Tamás and Ulbert, István}, doi = {10.1523/JNEUROSCI.1498-11.2011}, journal-iso = {J NEUROSCI}, journal = {JOURNAL OF NEUROSCIENCE}, volume = {31}, unique-id = {1611469}, issn = {0270-6474}, abstract = {Cortical electrical activity during nonrapid eye movement (non- REM) sleep is dominated by slow-wave activity (SWA). At larger spatial scales ( approximately 2-30 cm), investigated by scalp EEG recordings, SWA has been shown to propagate globally over wide cortical regions as traveling waves, which has been proposed to serve as a temporal framework for neural plasticity. However, whether SWA dynamics at finer spatial scales also reflects the orderly propagation has not previously been investigated in humans. To reveal the local, finer spatial scale ( approximately 1-6 cm) patterns of SWA propagation during non- REM sleep, electrocorticographic (ECoG) recordings were conducted from subdurally implanted electrode grids and a nonlinear correlation technique [mutual information (MI)] was implemented. MI analysis revealed spatial maps of correlations between cortical areas demonstrating SWA propagation directions, speed, and association strength. Highest correlations, indicating significant coupling, were detected during the initial positive-going deflection of slow waves. SWA propagated predominantly between adjacent cortical areas, albeit spatial noncontinuities were also frequently observed. MI analysis further uncovered significant convergence and divergence patterns. Areas receiving the most convergent activity were similar to those with high divergence rate, while reciprocal and circular propagation of SWA was also frequent. We hypothesize that SWA is characterized by distinct attributes depending on the spatial scale observed. At larger spatial scales, the orderly SWA propagation dominates; at the finer scale of the ECoG recordings, non-REM sleep is characterized by complex SWA propagation patterns.}, year = {2011}, eissn = {1529-2401}, pages = {8770-8779}, orcid-numbers = {Tihanyi, Benedek/0000-0003-2422-9355; Fabó, Dániel/0000-0001-5141-5351; Erőss, Loránd/0000-0002-5796-5546; Wittner, Lucia/0000-0001-6800-0953; Ulbert, István/0000-0001-9941-9159} } @article{MTMT:1606036, title = {Intrinsic functional architecture predicts electrically evoked responses in the human brain.}, url = {https://m2.mtmt.hu/api/publication/1606036}, author = {Keller, CJ and Bickel, S and Entz, László and Ulbert, István and Milham, MP and Kelly, C and Mehta, AD}, doi = {10.1073/pnas.1019750108}, journal-iso = {P NATL ACAD SCI USA}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {108}, unique-id = {1606036}, issn = {0027-8424}, abstract = {Adaptive brain function is characterized by dynamic interactions within and between neuronal circuits, often occurring at the time scale of milliseconds. These complex interactions between adjacent and noncontiguous brain areas depend on a functional architecture that is maintained even in the absence of input. Functional MRI studies carried out during rest (R-fMRI) suggest that this architecture is represented in low-frequency (<0.1 Hz) spontaneous fluctuations in the blood oxygen level-dependent signal that are correlated within spatially distributed networks of brain areas. These networks, collectively referred to as the brain's intrinsic functional architecture, exhibit a remarkable correspondence with patterns of task-evoked coactivation as well as maps of anatomical connectivity. Despite this striking correspondence, there is no direct evidence that this intrinsic architecture forms the scaffold that gives rise to faster processes relevant to information processing and seizure spread. Here, we demonstrate that the spatial distribution and magnitude of temporally correlated low-frequency fluctuations observed with R-fMRI during rest predict the pattern and magnitude of corticocortical evoked potentials elicited within 500 ms after single-pulse electrical stimulation of the cerebral cortex with intracranial electrodes. Across individuals, this relationship was found to be independent of the specific regions and functional systems probed. Our findings bridge the immense divide between the temporal resolutions of these distinct measures of brain function and provide strong support for the idea that the low-frequency signal fluctuations observed with R-fMRI maintain and update the intrinsic architecture underlying the brain's repertoire of functional responses.}, year = {2011}, eissn = {1091-6490}, pages = {10308-10313}, orcid-numbers = {Ulbert, István/0000-0001-9941-9159} } @article{MTMT:1362087, title = {Laminar analysis of slow wave activity in humans}, url = {https://m2.mtmt.hu/api/publication/1362087}, author = {Csercsa, Richárd and Dombovári, Balázs Gábor and Fabó, Dániel and Wittner, Lucia and Erőss, Loránd and Entz, László and Solyom, A and Rasonyi, G and Szűcs, Anna and Kelemen, Anna and Jakus, R and Juhos, V and Grand, László and Magony, Andor Dániel and Halász, Péter and Freund, Tamás and Maglóczky, Zsófia and Cash, SS and Papp, L and Karmos, György and Halgren, E and Ulbert, István}, doi = {10.1093/brain/awq169}, journal-iso = {BRAIN}, journal = {BRAIN}, volume = {133}, unique-id = {1362087}, issn = {0006-8950}, abstract = {Brain electrical activity is largely composed of oscillations at characteristic frequencies. These rhythms are hierarchically organized and are thought to perform important pathological and physiological functions. The slow wave is a fundamental cortical rhythm that emerges in deep non-rapid eye movement sleep. In animals, the slow wave modulates delta, theta, spindle, alpha, beta, gamma and ripple oscillations, thus orchestrating brain electrical rhythms in sleep. While slow wave activity can enhance epileptic manifestations, it is also thought to underlie essential restorative processes and facilitate the consolidation of declarative memories. Animal studies show that slow wave activity is composed of rhythmically recurring phases of widespread, increased cortical cellular and synaptic activity, referred to as active- or up-state, followed by cellular and synaptic inactivation, referred to as silent- or down-state. However, its neural mechanisms in humans are poorly understood, since the traditional intracellular techniques used in animals are inappropriate for investigating the cellular and synaptic/transmembrane events in humans. To elucidate the intracortical neuronal mechanisms of slow wave activity in humans, novel, laminar multichannel microelectrodes were chronically implanted into the cortex of patients with drug-resistant focal epilepsy undergoing cortical mapping for seizure focus localization. Intracortical laminar local field potential gradient, multiple-unit and single-unit activities were recorded during slow wave sleep, related to simultaneous electrocorticography, and analysed with current source density and spectral methods. We found that slow wave activity in humans reflects a rhythmic oscillation between widespread cortical activation and silence. Cortical activation was demonstrated as increased wideband (0.3-200 Hz) spectral power including virtually all bands of cortical oscillations, increased multiple- and single-unit activity and powerful inward transmembrane currents, mainly localized to the supragranular layers. Neuronal firing in the up-state was sparse and the average discharge rate of single cells was less than expected from animal studies. Action potentials at up-state onset were synchronized within +/-10 ms across all cortical layers, suggesting that any layer could initiate firing at up-state onset. These findings provide strong direct experimental evidence that slow wave activity in humans is characterized by hyperpolarizing currents associated with suppressed cell firing, alternating with high levels of oscillatory synaptic/transmembrane activity associated with increased cell firing. Our results emphasize the major involvement of supragranular layers in the genesis of slow wave activity.}, year = {2010}, eissn = {1460-2156}, pages = {2814-2829}, orcid-numbers = {Fabó, Dániel/0000-0001-5141-5351; Wittner, Lucia/0000-0001-6800-0953; Erőss, Loránd/0000-0002-5796-5546; Szűcs, Anna/0000-0002-9990-5787; Kelemen, Anna/0000-0003-3942-3409; Ulbert, István/0000-0001-9941-9159} } @article{MTMT:1234812, title = {The human K-complex represents an isolated cortical down-state.}, url = {https://m2.mtmt.hu/api/publication/1234812}, author = {Cash, SS and Halgren, E and Dehghani, N and Rossetti, AO and Thesen, T and Wang, C and Devinsky, O and Kuzniecky, R and Doyle, W and Madsen, JR and Bromfield, E and Erőss, Loránd and Halász, Péter and Karmos, György and Csercsa, Richárd and Wittner, Lucia and Ulbert, István}, doi = {10.1126/science.1169626}, journal-iso = {SCIENCE}, journal = {SCIENCE}, volume = {324}, unique-id = {1234812}, issn = {0036-8075}, abstract = {The electroencephalogram (EEG) is a mainstay of clinical neurology and is tightly correlated with brain function, but the specific currents generating human EEG elements remain poorly specified because of a lack of microphysiological recordings. The largest event in healthy human EEGs is the K- complex (KC), which occurs in slow-wave sleep. Here, we show that KCs are generated in widespread cortical areas by outward dendritic currents in the middle and upper cortical layers, accompanied by decreased broadband EEG power and decreased neuronal firing, which demonstrate a steep decline in network activity. Thus, KCs are isolated "down-states," a fundamental cortico-thalamic processing mode already characterized in animals. This correspondence is compatible with proposed contributions of the KC to sleep preservation and memory consolidation.}, year = {2009}, eissn = {1095-9203}, pages = {1084-1087}, orcid-numbers = {Erőss, Loránd/0000-0002-5796-5546; Wittner, Lucia/0000-0001-6800-0953; Ulbert, István/0000-0001-9941-9159} } @article{MTMT:208107, title = {Neuronavigation and fluoroscopy-assisted subdural strip electrode positioning: a simple method to increase intraoperative accuracy of strip localization in epilepsy surgery}, url = {https://m2.mtmt.hu/api/publication/208107}, author = {Erőss, Loránd and Bagó, Attila György and Entz, László and Fabó, Dániel and Halász, Péter and Balogh, Attila and Fedorcsák, Imre}, doi = {10.3171/2008.6.JNS17611}, journal-iso = {J NEUROSURG}, journal = {JOURNAL OF NEUROSURGERY}, volume = {110}, unique-id = {208107}, issn = {0022-3085}, year = {2009}, eissn = {1933-0693}, pages = {327-331}, orcid-numbers = {Erőss, Loránd/0000-0002-5796-5546; Fabó, Dániel/0000-0001-5141-5351} }