%0 Journal Article %J Neuroimage %D 2021 %T Modulation in cortical excitability disrupts information transfer in perceptual-level stimulus processing. %A Moheimanian, Ladan %A Paraskevopoulou, Sivylla E %A Adamek, Markus %A Schalk, Gerwin %A Peter Brunner %K Acoustic Stimulation %K Adult %K Aged %K Alpha Rhythm %K Auditory Cortex %K Brain Mapping %K Cortical Excitability %K Electrocorticography %K Female %K Humans %K Male %K Middle Aged %X

Despite significant interest in the neural underpinnings of behavioral variability, little light has been shed on the cortical mechanism underlying the failure to respond to perceptual-level stimuli. We hypothesized that cortical activity resulting from perceptual-level stimuli is sensitive to the moment-to-moment fluctuations in cortical excitability, and thus may not suffice to produce a behavioral response. We tested this hypothesis using electrocorticographic recordings to follow the propagation of cortical activity in six human subjects that responded to perceptual-level auditory stimuli. Here we show that for presentations that did not result in a behavioral response, the likelihood of cortical activity decreased from auditory cortex to motor cortex, and was related to reduced local cortical excitability. Cortical excitability was quantified using instantaneous voltage during a short window prior to cortical activity onset. Therefore, when humans are presented with an auditory stimulus close to perceptual-level threshold, moment-by-moment fluctuations in cortical excitability determine whether cortical responses to sensory stimulation successfully connect auditory input to a resultant behavioral response.

%B Neuroimage %V 243 %P 118498 %8 11/2021 %G eng %R 10.1016/j.neuroimage.2021.118498 %0 Journal Article %J Neuroimage %D 2021 %T Within-subject reaction time variability: Role of cortical networks and underlying neurophysiological mechanisms. %A Paraskevopoulou, Sivylla E %A Coon, William G %A Peter Brunner %A Miller, Kai J %A Schalk, Gerwin %K Adult %K Algorithms %K Alpha Rhythm %K Cerebral Cortex %K Connectome %K Electrocorticography %K Female %K Gamma Rhythm %K Humans %K Male %K Middle Aged %K Nerve Net %K Psychomotor Performance %K Reaction Time %K Young Adult %X

Variations in reaction time are a ubiquitous characteristic of human behavior. Extensively documented, they have been successfully modeled using parameters of the subject or the task, but the neural basis of behavioral reaction time that varies within the same subject and the same task has been minimally studied. In this paper, we investigate behavioral reaction time variance using 28 datasets of direct cortical recordings in humans who engaged in four different types of simple sensory-motor reaction time tasks. Using a previously described technique that can identify the onset of population-level cortical activity and a novel functional connectivity algorithm described herein, we show that the cumulative latency difference of population-level neural activity across the task-related cortical network can explain up to 41% of the trial-by-trial variance in reaction time. Furthermore, we show that reaction time variance may primarily be due to the latencies in specific brain regions and demonstrate that behavioral latency variance is accumulated across the whole task-related cortical network. Our results suggest that population-level neural activity monotonically increases prior to movement execution, and that trial-by-trial changes in that increase are, in part, accounted for by inhibitory activity indexed by low-frequency oscillations. This pre-movement neural activity explains 19% of the measured variance in neural latencies in our data. Thus, our study provides a mechanistic explanation for a sizable fraction of behavioral reaction time when the subject's task is the same from trial to trial.

%B Neuroimage %V 237 %P 118127 %8 08/2021 %G eng %R 10.1016/j.neuroimage.2021.118127 %0 Journal Article %J J Neurooncol %D 2020 %T Potential differences between monolingual and bilingual patients in approach and outcome after awake brain surgery. %A ReFaey, Karim %A Tripathi, Shashwat %A Bhargav, Adip G %A Grewal, Sanjeet S %A Middlebrooks, Erik H %A Sabsevitz, David S %A Jentoft, Mark %A Peter Brunner %A Wu, Adela %A Tatum, William O %A Ritaccio, Anthony %A Chaichana, Kaisorn L %A Quinones-Hinojosa, Alfredo %K Brain Mapping %K Brain Neoplasms %K Craniotomy %K Female %K Follow-Up Studies %K Glioma %K Humans %K Incidence %K Language %K Male %K Middle Aged %K Monitoring, Intraoperative %K Prognosis %K Retrospective Studies %K Seizures %K United States %K Wakefulness %X

INTRODUCTION: 20.8% of the United States population and 67% of the European population speak two or more languages. Intraoperative different languages, mapping, and localization are crucial. This investigation aims to address three questions between BL and ML patients: (1) Are there differences in complications (i.e. seizures) and DECS techniques during intra-operative brain mapping? (2) Is EOR different? and (3) Are there differences in the recovery pattern post-surgery?

METHODS: Data from 56 patients that underwent left-sided awake craniotomy for tumors infiltrating possible dominant hemisphere language areas from September 2016 to June 2019 were identified and analyzed in this study; 14 BL and 42 ML control patients. Patient demographics, education level, and the age of language acquisition were documented and evaluated. fMRI was performed on all participants.

RESULTS: 0 (0%) BL and 3 (7%) ML experienced intraoperative seizures (P = 0.73). BL patients received a higher direct DECS current in comparison to the ML patients (average = 4.7, 3.8, respectively, P = 0.03). The extent of resection was higher in ML patients in comparison to the BL patients (80.9 vs. 64.8, respectively, P = 0.04). The post-operative KPS scores were higher in BL patients in comparison to ML patients (84.3, 77.4, respectively, P = 0.03). BL showed lower drop in post-operative KPS in comparison to ML patients (- 4.3, - 8.7, respectively, P = 0.03).

CONCLUSION: We show that BL patients have a lower incidence of intra-operative seizures, lower EOR, higher post-operative KPS and tolerate higher DECS current, in comparison to ML patients.

%B J Neurooncol %V 148 %P 587-598 %8 07/2020 %G eng %N 3 %R 10.1007/s11060-020-03554-0 %0 Journal Article %J J Neurosurg Pediatr %D 2014 %T Real-time functional mapping: potential tool for improving language outcome in pediatric epilepsy surgery. %A Korostenskaja, Milena %A Chen, Po-Ching %A Salinas, Christine M %A Westerveld, Michael %A Peter Brunner %A Gerwin Schalk %A Cook, Jane C %A Baumgartner, James %A Lee, Ki H %K Adolescent %K Anticonvulsants %K Brain Mapping %K Cerebral Cortex %K Electric Stimulation %K Electroencephalography %K Epilepsies, Partial %K Female %K Humans %K Language %K Neuropsychological Tests %K Sensitivity and Specificity %K Speech %X

Accurate language localization expands surgical treatment options for epilepsy patients and reduces the risk of postsurgery language deficits. Electrical cortical stimulation mapping (ESM) is considered to be the clinical gold standard for language localization. While ESM affords clinically valuable results, it can be poorly tolerated by children, requires active participation and compliance, carries a risk of inducing seizures, is highly time consuming, and is labor intensive. Given these limitations, alternative and/or complementary functional localization methods such as analysis of electrocorticographic (ECoG) activity in high gamma frequency band in real time are needed to precisely identify eloquent cortex in children. In this case report, the authors examined 1) the use of real-time functional mapping (RTFM) for language localization in a high gamma frequency band derived from ECoG to guide surgery in an epileptic pediatric patient and 2) the relationship of RTFM mapping results to postsurgical language outcomes. The authors found that RTFM demonstrated relatively high sensitivity (75%) and high specificity (90%) when compared with ESM in a "next-neighbor" analysis. While overlapping with ESM in the superior temporal region, RTFM showed a few other areas of activation related to expressive language function, areas that were eventually resected during the surgery. The authors speculate that this resection may be associated with observed postsurgical expressive language deficits. With additional validation in more subjects, this finding would suggest that surgical planning and associated assessment of the risk/benefit ratio would benefit from information provided by RTFM mapping.

%B J Neurosurg Pediatr %V 14 %P 287-95 %8 09/2014 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/24995815 %N 3 %R 10.3171/2014.6.PEDS13477 %0 Journal Article %J Neuroimage %D 2011 %T Spatiotemporal dynamics of electrocorticographic high gamma activity during overt and covert word repetition. %A Pei, Xiao-Mei %A Leuthardt, E C %A Charles M Gaona %A Peter Brunner %A Jonathan Wolpaw %A Gerwin Schalk %K Adolescent %K Adult %K Brain %K Brain Mapping %K Electroencephalography %K Female %K Humans %K Male %K Middle Aged %K Signal Processing, Computer-Assisted %K Verbal Behavior %X

Language is one of the defining abilities of humans. Many studies have characterized the neural correlates of different aspects of language processing. However, the imaging techniques typically used in these studies were limited in either their temporal or spatial resolution. Electrocorticographic (ECoG) recordings from the surface of the brain combine high spatial with high temporal resolution and thus could be a valuable tool for the study of neural correlates of language function. In this study, we defined the spatiotemporal dynamics of ECoG activity during a word repetition task in nine human subjects. ECoG was recorded while each subject overtly or covertly repeated words that were presented either visually or auditorily. ECoG amplitudes in the high gamma (HG) band confidently tracked neural changes associated with stimulus presentation and with the subject's verbal response. Overt word production was primarily associated with HG changes in the superior and middle parts of temporal lobe, Wernicke's area, the supramarginal gyrus, Broca's area, premotor cortex (PMC), primary motor cortex. Covert word production was primarily associated with HG changes in superior temporal lobe and the supramarginal gyrus. Acoustic processing from both auditory stimuli as well as the subject's own voice resulted in HG power changes in superior temporal lobe and Wernicke's area. In summary, this study represents a comprehensive characterization of overt and covert speech using electrophysiological imaging with high spatial and temporal resolution. It thereby complements the findings of previous neuroimaging studies of language and thus further adds to current understanding of word processing in humans.

%B Neuroimage %V 54 %P 2960-72 %8 02/2011 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/21029784 %N 4 %R 10.1016/j.neuroimage.2010.10.029 %0 Journal Article %J J Neural Eng %D 2010 %T Does the 'P300' speller depend on eye gaze?. %A Peter Brunner %A Joshi, S %A S Briskin %A Jonathan Wolpaw %A H Bischof %A Gerwin Schalk %K Adult %K Event-Related Potentials, P300 %K Eye Movements %K Female %K Humans %K Male %K Middle Aged %K Models, Neurological %K Photic Stimulation %K User-Computer Interface %K Young Adult %X

Many people affected by debilitating neuromuscular disorders such as amyotrophic lateral sclerosis, brainstem stroke or spinal cord injury are impaired in their ability to, or are even unable to, communicate. A brain-computer interface (BCI) uses brain signals, rather than muscles, to re-establish communication with the outside world. One particular BCI approach is the so-called 'P300 matrix speller' that was first described by Farwell and Donchin (1988 Electroencephalogr. Clin. Neurophysiol. 70 510-23). It has been widely assumed that this method does not depend on the ability to focus on the desired character, because it was thought that it relies primarily on the P300-evoked potential and minimally, if at all, on other EEG features such as the visual-evoked potential (VEP). This issue is highly relevant for the clinical application of this BCI method, because eye movements may be impaired or lost in the relevant user population. This study investigated the extent to which the performance in a 'P300' speller BCI depends on eye gaze. We evaluated the performance of 17 healthy subjects using a 'P300' matrix speller under two conditions. Under one condition ('letter'), the subjects focused their eye gaze on the intended letter, while under the second condition ('center'), the subjects focused their eye gaze on a fixation cross that was located in the center of the matrix. The results show that the performance of the 'P300' matrix speller in normal subjects depends in considerable measure on gaze direction. They thereby disprove a widespread assumption in BCI research, and suggest that this BCI might function more effectively for people who retain some eye-movement control. The applicability of these findings to people with severe neuromuscular disabilities (particularly in eye-movements) remains to be determined.

%B J Neural Eng %V 7 %P 056013 %8 10/2010 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/20858924 %N 5 %R 10.1088/1741-2560/7/5/056013 %0 Journal Article %J Epilepsy Behav %D 2009 %T A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans. %A Peter Brunner %A A L Ritaccio %A Lynch, Timothy M %A Emrich, Joseph F %A Adam J Wilson %A Williams, Justin C %A Aarnoutse, Erik J %A Ramsey, Nick F %A Leuthardt, E C %A H Bischof %A Gerwin Schalk %K Adult %K Brain Mapping %K Cerebral Cortex %K Electric Stimulation %K Electrodes, Implanted %K Electroencephalography %K Epilepsy %K Female %K Humans %K Male %K Middle Aged %K Practice Guidelines as Topic %K Signal Processing, Computer-Assisted %K Young Adult %X

Functional mapping of eloquent cortex is often necessary prior to invasive brain surgery, but current techniques that derive this mapping have important limitations. In this article, we demonstrate the first comprehensive evaluation of a rapid, robust, and practical mapping system that uses passive recordings of electrocorticographic signals. This mapping procedure is based on the BCI2000 and SIGFRIED technologies that we have been developing over the past several years. In our study, we evaluated 10 patients with epilepsy from four different institutions and compared the results of our procedure with the results derived using electrical cortical stimulation (ECS) mapping. The results show that our procedure derives a functional motor cortical map in only a few minutes. They also show a substantial concurrence with the results derived using ECS mapping. Specifically, compared with ECS maps, a next-neighbor evaluation showed no false negatives, and only 0.46 and 1.10% false positives for hand and tongue maps, respectively. In summary, we demonstrate the first comprehensive evaluation of a practical and robust mapping procedure that could become a new tool for planning of invasive brain surgeries.

%B Epilepsy Behav %V 15 %P 278-86 %8 07/2009 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/19366638 %N 3 %R 10.1016/j.yebeh.2009.04.001 %0 Journal Article %J Neuroimage %D 2008 %T Real-time detection of event-related brain activity. %A Gerwin Schalk %A Leuthardt, E C %A Peter Brunner %A Ojemann, J G %A Lester A Gerhardt %A Jonathan Wolpaw %K Adult %K Algorithms %K Brain Mapping %K Computer Systems %K Diagnosis, Computer-Assisted %K Electroencephalography %K Epilepsy %K Evoked Potentials %K Female %K Humans %K Male %K Pattern Recognition, Automated %K Reproducibility of Results %K Sensitivity and Specificity %X

The complexity and inter-individual variation of brain signals impedes real-time detection of events in raw signals. To convert these complex signals into results that can be readily understood, current approaches usually apply statistical methods to data from known conditions after all data have been collected. The capability to provide meaningful visualization of complex brain signals without the requirement to initially collect data from all conditions would provide a new tool, essentially a new imaging technique, that would open up new avenues for the study of brain function. Here we show that a new analysis approach, called SIGFRIED, can overcome this serious limitation of current methods. SIGFRIED can visualize brain signal changes without requiring prior data collection from all conditions. This capacity is particularly well suited to applications in which comprehensive prior data collection is impossible or impractical, such as intraoperative localization of cortical function or detection of epileptic seizures.

%B Neuroimage %V 43 %P 245-9 %8 11/2008 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/18718544 %N 2 %R 10.1016/j.neuroimage.2008.07.037