02268nas a2200337 4500008004100000022001400041245011100055210006900166260001200235300001100247490000800258520124200266653002501508653001001533653000901543653001701552653002001569653001801589653002601607653002501633653001101658653001101669653000901680653001601689100002301705700003201728700001901760700001901779700001901798856011301817 2021 eng d a1095-957200aModulation in cortical excitability disrupts information transfer in perceptual-level stimulus processing.0 aModulation in cortical excitability disrupts information transfe c11/2021 a1184980 v2433 a

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.

10aAcoustic Stimulation10aAdult10aAged10aAlpha Rhythm10aAuditory Cortex10aBrain Mapping10aCortical Excitability10aElectrocorticography10aFemale10aHumans10aMale10aMiddle Aged1 aMoheimanian, Ladan1 aParaskevopoulou, Sivylla, E1 aAdamek, Markus1 aSchalk, Gerwin1 aBrunner, Peter uhttps://neurotechcenter.org/publications/2021/modulation-cortical-excitability-disrupts-information-transfer03596nas a2200505 4500008004100000022001400041245010700055210006900162260001200231300001300243490000700256520217800263653002502441653001502466653001002481653002502491653001802516653001602534653002002550653002402570653002702594653001302621653002202634653001102656653001102667653000902678653001602687653002902703653002302732653002302755653001802778653002202796653001702818653001502835100002202850700001802872700002902890700002402919700002002943700001802963700002302981700001903004700001903023856004803042 2011 eng d a1529-240100aNonuniform high-gamma (60-500 Hz) power changes dissociate cognitive task and anatomy in human cortex.0 aNonuniform highgamma 60500 Hz power changes dissociate cognitive c02/2011 a2091-1000 v313 a

High-gamma-band (>60 Hz) power changes in cortical electrophysiology are a reliable indicator of focal, event-related cortical activity. Despite discoveries of oscillatory subthreshold and synchronous suprathreshold activity at the cellular level, there is an increasingly popular view that high-gamma-band amplitude changes recorded from cellular ensembles are the result of asynchronous firing activity that yields wideband and uniform power increases. Others have demonstrated independence of power changes in the low- and high-gamma bands, but to date, no studies have shown evidence of any such independence above 60 Hz. Based on nonuniformities in time-frequency analyses of electrocorticographic (ECoG) signals, we hypothesized that induced high-gamma-band (60-500 Hz) power changes are more heterogeneous than currently understood. Using single-word repetition tasks in six human subjects, we showed that functional responsiveness of different ECoG high-gamma sub-bands can discriminate cognitive task (e.g., hearing, reading, speaking) and cortical locations. Power changes in these sub-bands of the high-gamma range are consistently present within single trials and have statistically different time courses within the trial structure. Moreover, when consolidated across all subjects within three task-relevant anatomic regions (sensorimotor, Broca's area, and superior temporal gyrus), these behavior- and location-dependent power changes evidenced nonuniform trends across the population. Together, the independence and nonuniformity of power changes across a broad range of frequencies suggest that a new approach to evaluating high-gamma-band cortical activity is necessary. These findings show that in addition to time and location, frequency is another fundamental dimension of high-gamma dynamics.

10aAcoustic Stimulation10aAdolescent10aAdult10aAnalysis of Variance10aBrain Mapping10aBrain Waves10aCerebral Cortex10aCognition Disorders10aElectroencephalography10aEpilepsy10aEvoked Potentials10aFemale10aHumans10aMale10aMiddle Aged10aNeuropsychological Tests10aNonlinear Dynamics10aPhotic Stimulation10aReaction Time10aSpectrum Analysis10aTime Factors10aVocabulary1 aGaona, Charles, M1 aSharma, Mohit1 aFreudenberg, Zachary, V.1 aBreshears, Jonathan1 aBundy, David, T1 aRoland, Jarod1 aBarbour, Dennis, L1 aSchalk, Gerwin1 aLeuthardt, E C uhttp://www.ncbi.nlm.nih.gov/pubmed/2130724604454nas a2200433 4500008004100000022001400041245010500055210006900160260001200229300001100241490000700252520325900259653002503518653001503543653001003558653001803568653002003586653002803606653002703634653001303661653001103674653001103685653000903696653002203705653001603727653002303743653001103766653002003777653001603797100001603813700002303829700001903852700001803871700001803889700002403907700002203931700001903953856004803972 2010 eng d a1524-404000aElectrocorticographic frequency alteration mapping for extraoperative localization of speech cortex.0 aElectrocorticographic frequency alteration mapping for extraoper c02/2010 aE407-90 v663 a

OBJECTIVE: 

Electrocortical stimulation (ECS) has long been established for delineating eloquent cortex in extraoperative mapping. However, ECS is still coarse and inefficient in delineating regions of functional cortex and can be hampered by afterdischarges. Given these constraints, an adjunct approach to defining motor cortex is the use of electrocorticographic (ECoG) signal changes associated with active regions of cortex. The broad range of frequency oscillations are categorized into 2 main groups with respect to sensorimotor cortex: low-frequency bands (LFBs) and high-frequency bands (HFBs). The LFBs tend to show a power reduction, whereas the HFBs show power increases with cortical activation. These power changes associated with activated cortex could potentially provide a powerful tool in delineating areas of speech cortex. We explore ECoG signal alterations as they occur with activated region of speech cortex and its potential in clinical brain mapping applications.

METHODS: 

We evaluated 7 patients who underwent invasive monitoring for seizure localization. Each had extraoperative ECS mapping to identify speech cortex. Additionally, all subjects performed overt speech tasks with an auditory or a visual cue to identify associated frequency power changes in regard to location and degree of concordance with ECS results.

RESULTS: 

Electrocorticographic frequency alteration mapping (EFAM) had an 83.9% sensitivity and a 40.4% specificity in identifying any language site when considering both frequency bands and both stimulus cues. Electrocorticographic frequency alteration mapping was more sensitive in identifying the Wernicke area (100%) than the Broca area (72.2%). The HFB is uniquely suited to identifying the Wernicke area, whereas a combination of the HFB and LFB is important for Broca localization.

CONCLUSION: 

The concordance between stimulation and spectral power changes demonstrates the possible utility of EFAM as an adjunct method to improve the efficiency and resolution of identifying speech cortex.

10aAcoustic Stimulation10aAdolescent10aAdult10aBrain Mapping10aCerebral Cortex10aChi-Square Distribution10aElectroencephalography10aEpilepsy10aFemale10aHumans10aMale10aMass Spectrometry10aMiddle Aged10aPhotic Stimulation10aSpeech10aVerbal Behavior10aYoung Adult1 aWu, Melinda1 aWisneski, Kimberly1 aSchalk, Gerwin1 aSharma, Mohit1 aRoland, Jarod1 aBreshears, Jonathan1 aGaona, Charles, M1 aLeuthardt, E C uhttp://www.ncbi.nlm.nih.gov/pubmed/20087111