@article{MTMT:2717967,
	title = {Evoked effective connectivity of the human neocortex},
	url = {https://m2.mtmt.hu/api/publication/2717967},
	author = {Entz, László and Tóth, Emília and Keller, CJ and Bickel, S and Groppe, DM and Fabó, Dániel and Kozák, Lajos Rudolf and Erőss, Loránd and Ulbert, István and Mehta, AD},
	doi = {10.1002/hbm.22581},
	journal-iso = {HUM BRAIN MAPP},
	journal = {HUMAN BRAIN MAPPING},
	volume = {35},
	unique-id = {2717967},
	issn = {1065-9471},
	abstract = {The role of cortical connectivity in brain function and pathology is increasingly being recognized. While in vivo magnetic resonance imaging studies have provided important insights into anatomical and functional connectivity, these methodologies are limited in their ability to detect electrophysiological activity and the causal relationships that underlie effective connectivity. Here, we describe results of cortico-cortical evoked potential (CCEP) mapping using single pulse electrical stimulation in 25 patients undergoing seizure monitoring with subdural electrode arrays. Mapping was performed by stimulating adjacent electrode pairs and recording CCEPs from the remainder of the electrode array. CCEPs reliably revealed functional networks and showed an inverse relationship to distance between sites. Coregistration to Brodmann areas (BA) permitted group analysis. Connections were frequently directional with 43% of early responses and 50% of late responses of connections reflecting relative dominance of incoming or outgoing connections. The most consistent connections were seen as outgoing from motor cortex, BA6-BA9, somatosensory (SS) cortex, anterior cingulate cortex, and Broca's area. Network topology revealed motor, SS, and premotor cortices along with BA9 and BA10 and language areas to serve as hubs for cortical connections. BA20 and BA39 demonstrated the most consistent dominance of outdegree connections, while BA5, BA7, auditory cortex, and anterior cingulum demonstrated relatively greater indegree. This multicenter, large-scale, directional study of local and long-range cortical connectivity using direct recordings from awake, humans will aid the interpretation of noninvasive functional connectome studies. Hum Brain Mapp, 2014. (c) 2014 Wiley Periodicals, Inc.},
	year = {2014},
	eissn = {1097-0193},
	pages = {5736-5753},
	orcid-numbers = {Fabó, Dániel/0000-0001-5141-5351; Kozák, Lajos Rudolf/0000-0003-0368-3663; Erőss, Loránd/0000-0002-5796-5546; Ulbert, István/0000-0001-9941-9159}
}

@article{MTMT:2736859,
	title = {Mapping human brain networks with cortico-cortical evoked potentials},
	url = {https://m2.mtmt.hu/api/publication/2736859},
	author = {Keller, CJ and Honey, CJ and Mégevand, P and Entz, László and Ulbert, István and Mehta, AD},
	doi = {10.1098/rstb.2013.0528},
	journal-iso = {PHILOS T ROY SOC B},
	journal = {PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B - BIOLOGICAL SCIENCES},
	volume = {369},
	unique-id = {2736859},
	issn = {0962-8436},
	abstract = {The cerebral cortex forms a sheet of neurons organized into a network of interconnected modules that is highly expanded in humans and presumably enables our most refined sensory and cognitive abilities. The links of this network form a fundamental aspect of its organization, and a great deal of research is focusing on understanding how information flows within and between different regions. However, an often-overlooked element of this connectivity regards a causal, hierarchical structure of regions, whereby certain nodes of the cortical network may exert greater influence over the others. While this is difficult to ascertain non-invasively, patients undergoing invasive electrode monitoring for epilepsy provide a unique window into this aspect of cortical organization. In this review, we highlight the potential for corticocortical evoked potential (CCEP) mapping to directly measure neuronal propagation across large-scale brain networks with spatio-temporal resolution that is superior to traditional neuroimaging methods.We first introduce effective connectivity and discuss the mechanisms underlying CCEP generation. Next, we highlight how CCEP mapping has begun to provide insight into the neural basis of non-invasive imaging signals. Finally, we present a novel approach to perturbing and measuring brain network function during cognitive processing. The direct measurement of CCEPs in response to electrical stimulation represents a potentially powerful clinical and basic science tool for probing the large-scale networks of the human cerebral cortex. © 2014 The Author(s) Published by the Royal Society. All rights reserved.},
	keywords = {STIMULATION; electrocorticography; Graph theory; Effective connectivity; Cortico-cortical evoked potential},
	year = {2014},
	eissn = {1471-2970},
	orcid-numbers = {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}
}