@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:3359005, title = {Cortico-cortical evoked potentials and stimulation-elicited gamma activity preferentially propagate from lower- to higher-order visual areas.}, url = {https://m2.mtmt.hu/api/publication/3359005}, author = {Matsuzaki, N and Juhász, Csaba and Asano, E}, doi = {10.1016/j.clinph.2013.02.007}, journal-iso = {CLIN NEUROPHYSIOL}, journal = {CLINICAL NEUROPHYSIOLOGY}, volume = {124}, unique-id = {3359005}, issn = {1388-2457}, abstract = {OBJECTIVE: The lower-order visual cortex in the medial-occipital region is suggested to send feed-forward signals to the higher-order visual cortex including ventral-occipital-temporal and dorsal-occipital regions. We determined how stimulation-elicited cortical-signals propagate between lower- and higher-order visual cortices, and whether the magnitudes of stimulation-elicited cortical-signals recorded in the higher-order visual cortex differed from those recorded in the lower-order one. METHODS: We studied 10 patients with focal epilepsy who underwent extraoperative electrocorticography recording. Trains of 1-Hz stimuli with an intensity of 3 mA were delivered to an electrode pair within the medial-occipital region; then, cortico-cortical evoked-potential (CCEP) and stimulation-elicited gamma-activity at 80-150 Hz were measured in the ventral-occipital-temporal and dorsal-occipital regions. Likewise, CCEP and stimulation-elicited gamma-activity, driven by stimuli within the higher-order visual cortex, were measured in the lower-order visual cortex. RESULTS: CCEPs generated, via feed-forward propagations, in the higher-order visual cortex were significantly larger than those generated, via feed-back propagations, in the lower-order visual cortex. Stimulation of the lower-order visual cortex elicited augmentation of gamma-activity in the higher-order visual cortex after the preceding CCEP subsided. CONCLUSION: The propagation manners of stimulation-elicited cortical-signals differ between feed-forward and feed-back directions in the human occipital lobe. SIGNIFICANCE: : Such difference may need to be taken into consideration for future clinical application of CCEPs and stimulation-elicited gamma-augmentation in presurgical evaluation for epilepsy surgery.}, keywords = {Adolescent; Female; Male; Humans; Child; Electrodes, Implanted; Electric Stimulation; Epilepsy/*pathology; Functional Laterality; Electroencephalography; Reaction Time; Biophysics; *Brain Mapping; Neural Pathways/*physiopathology; Evoked Potentials/*physiology; Visual Cortex/*physiopathology; Nerve Net/*physiopathology}, year = {2013}, eissn = {1872-8952}, pages = {1290-1296} } @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} }