@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:2716516,
	title = {Corticocortical evoked potentials reveal projectors and integrators in human brain networks.},
	url = {https://m2.mtmt.hu/api/publication/2716516},
	author = {Keller, CJ and Honey, CJ and Entz, László and Bickel, S and Groppe, DM and Tóth, Emília and Ulbert, István and Lado, FA and Mehta, AD},
	doi = {10.1523/JNEUROSCI.4289-13.2014},
	journal-iso = {J NEUROSCI},
	journal = {JOURNAL OF NEUROSCIENCE},
	volume = {34},
	unique-id = {2716516},
	issn = {0270-6474},
	abstract = {The cerebral cortex is composed of subregions whose 
		functional specialization is largely determined by their 
		incoming and outgoing connections with each other. In the 
		present study, we asked which cortical regions can exert the 
		greatest influence over other regions and the cortical 
		network as a whole. Previous research on this question has 
		relied on coarse anatomy (mapping large fiber pathways) or 
		functional connectivity (mapping inter-regional statistical 
		dependencies in ongoing activity). Here we combined direct 
		electrical stimulation with recordings from the cortical 
		surface to provide a novel insight into directed, inter-
		regional influence within the cerebral cortex of awake 
		humans. These networks of directed interaction were 
		reproducible across strength thresholds and across subjects. 
		Directed network properties included (1) a decrease in the 
		reciprocity of connections with distance; (2) major projector 
		nodes (sources of influence) were found in peri-Rolandic 
		cortex and posterior, basal and polar regions of the temporal 
		lobe; and (3) major receiver nodes (receivers of influence) 
		were found in anterolateral frontal, superior parietal, and 
		superior temporal regions. Connectivity maps derived from 
		electrical stimulation and from resting electrocorticography 
		(ECoG) correlations showed similar spatial distributions for 
		the same source node. However, higher-level network topology 
		analysis revealed differences between electrical stimulation 
		and ECoG that were partially related to the reciprocity of 
		connections. Together, these findings inform our 
		understanding of large-scale corticocortical influence as 
		well as the interpretation of functional connectivity 
		networks.},
	year = {2014},
	eissn = {1529-2401},
	pages = {9152-9163},
	orcid-numbers = {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}
}