Spatio-temporal dynamics of working memory maintenance and scanning of verbal information

ObjectiveDuring verbal communication, humans briefly maintain mental representations of speech sounds conveying verbal information, and constantly scan these representations for comparison to incoming information. We determined the spatio-temporal dynamics of such short-term maintenance and subsequent scanning of verbal information, by intracranially measuring high-gamma activity at 70–110 Hz during a working memory task.MethodsPatients listened to a stimulus set of two or four spoken letters and were instructed to remember those letters over a two-second interval, following which they were asked to determine if a subsequent target letter had been presented earlier in that trial’s stimulus set.ResultsAuditory presentation of letter stimuli sequentially elicited high-gamma augmentation bilaterally in the superior-temporal and pre-central gyri. During the two-second maintenance period, high-gamma activity was augmented in the left pre-central gyrus, and this effect was larger during the maintenance of stimulus sets consisting of four compared to two letters. During the scanning period following target presentation, high-gamma augmentation involved the left inferior-frontal and supra-marginal gyri.ConclusionsShort-term maintenance of verbal information is, at least in part, supported by the left pre-central gyrus, whereas scanning by the left inferior-frontal and supra-marginal gyri.SignificanceThe cortical structures involved in short-term maintenance and scanning of speech stimuli were segregated with an excellent temporal resolution.     

A distributed network supports spatiotemporal cerebral dynamics of visual naming

ObjectiveCerebral spatiotemporal dynamics of visual naming were investigated in epilepsy patients undergoing stereo-electroencephalography (SEEG) monitoring.MethodsBrain networks were defined by Parcel-Activation-Resection-Symptom matching (PARS) approach by matching high-gamma (50–150 Hz) modulations (HGM) in neuroanatomic parcels during visual naming, with neuropsychological outcomes after resection/ablation of those parcels. Brain parcels with >50% electrode contacts simultaneously showing significant HGM were aligned, to delineate spatiotemporal course of naming-related HGM.ResultsIn 41 epilepsy patients, neuroanatomic parcels showed sequential yet temporally overlapping HGM course during visual naming. From bilateral occipital lobes, HGM became increasingly left lateralized, coursing through limbic system. Bilateral superior temporal HGM was noted around response time, and right frontal HGM thereafter. Correlations between resected/ablated parcels, and post-surgical neuropsychological outcomes showed specific regional groupings.ConclusionsConvergence of data from spatiotemporal course of HGM during visual naming, and functional role of specific parcels inferred from neuropsychological deficits after resection/ablation of those parcels, support a model with six cognitive subcomponents of visual naming having overlapping temporal profiles.SignificanceCerebral substrates supporting visual naming are bilaterally distributed with relative hemispheric contribution dependent on cognitive demands at a specific time. PARS approach can be extended to study other cognitive and functional brain networks.     

The dynamics of language-related high-gamma activity assessed on a spatially-normalized brain

ObjectiveWe developed a novel technique of spatial normalization of subdural electrode positions across subjects and assessed the spatial–temporal dynamics of high-gamma activity (HGA) in the dominant hemisphere elicited by three distinct language tasks.MethodsThe normalization process was applied to 1512 subdural electrodes implanted in 21 patients with intractable epilepsy. We projected each task-related HGA profile onto a normalized brain.ResultsThe word interpretation task initially elicited HGA augmentation in the bilateral fusiform gyri at 100 ms after stimulus onsets, subsequently in the left posterior middle temporal gyrus, in the left ventral premotor cortex at 200 ms and in the left middle and left inferior frontal gyri at 300 ms and after. The picture naming task elicited HGA augmentation in few sites in the left frontal lobe. The verb generation task elicited HGA in the left superior temporal gyrus at 100–600 ms. Common HGA augmentation elicited by all three tasks was noted in the left posterior-middle temporal and left ventral premotor cortices.ConclusionsThe spatial–temporal dynamics of language-related HGA were demonstrated on a spatially-normalized brain template.SignificanceThis study externally validated the spatial and temporal dynamics of language processing suggested by previous neuroimaging and electrophysiological studies.     

Brain network dynamics in the human articulatory loop

Objective

The articulatory loop is a fundamental component of language function, involved in the short-term buffer of auditory information followed by its vocal reproduction. We characterized the network dynamics of the human articulatory loop, using invasive recording and stimulation.

Gamma activity modulated by picture and auditory naming tasks: Intracranial recording in patients with focal epilepsy

ObjectiveWe measured the spatial, temporal and developmental patterns of gamma activity augmented by picture- and auditory-naming tasks and determined the clinical significance of naming-related gamma-augmentation.MethodsWe studied 56 epileptic patients (age: 4–56 years) who underwent extraoperative electrocorticography. The picture-naming task consisted of naming of a visually-presented object; the auditory-naming task consisted of answering an auditorily-presented sentence question.ResultsNaming-related gamma-augmentation at 50–120 Hz involved the modality-specific sensory cortices during stimulus presentation and inferior-Rolandic regions during responses. Gamma-augmentation in the bilateral occipital and inferior/medial-temporal regions was more intense in the picture-naming than auditory-naming task, whereas that in the bilateral superior-temporal, left middle-temporal, left inferior-parietal, and left frontal regions was more intense in the auditory-naming task. Patients above 10 years old, compared to those younger, showed more extensive gamma-augmentation in the left dorsolateral-premotor region. Resection of sites showing naming-related gamma-augmentation in the left hemisphere assumed to contain essential language function was associated with increased risk of post-operative language deficits requiring speech therapy (p < 0.05).ConclusionsMeasurement of gamma-augmentation elicited by either naming task was useful to predict postoperative language deficits.SignificanceA smaller degree of frontal engagement in the picture-naming task can be explained by no requirement of syntactic processing or less working memory load. More extensive gamma-augmentation in the left dorsolateral-premotor region in older individuals may suggest more proficient processing by the mature brain.     

Lesion analysis of language production deficits in aphasia

Background: Three aspects of language production are impaired to different degrees in individuals with post-stroke aphasia: ability to repeat words and nonwords, name pictures, and produce sentences. These impairments often persist into the chronic stages, and the neuroanatomical distribution of lesions associated with chronicity of each of these impairments is incompletely understood.

Aims: The primary objective of this study was to investigate the lesion correlates of picture naming, sentence production, and nonword repetition deficits in the same participant group because most prior lesion studies have mapped single language impairments. The broader goal of this study was to investigate the extent and degree of overlap and uniqueness among lesions resulting in these deficits in order to advance the current understanding of functional subdivision of neuroanatomical regions involved in language production.

Methods & Procedures: In this study, lesion-symptom mapping was used to determine if specific cortical regions are associated with nonword repetition, picture naming, and sentence production scores. Structural brain images and behavioural performance of 31 individuals with post-stroke left hemisphere lesions and a diagnosis of aphasia were used in the lesion analysis.

Outcomes & Results: Each impairment was associated with mostly unique, but a few shared lesions. Overall, sentence and repetition deficits were associated with left anterior perisylvian lesions, including the pars opercularis and triangularis of the inferior frontal lobe, anterior superior temporal gyrus, anterior portions of the supramarginal gyrus, the putamen, and anterior portions of the insula. In contrast, impaired picture naming was associated with posterior perisylvian lesions including major portions of the inferior parietal lobe and middle temporal gyrus. The distribution of lesions in the insula was consistent with this antero-posterior perisylvian gradient. Significant voxels in the posterior planum temporale were associated with a combination of all three deficits.

Conclusions: These findings emphasise the participation of each perisylvian region in multiple linguistic functions, suggesting a many(functions)-to-many(networks) framework while also identifying functional subdivisions within each region.     

Cortical gamma‐oscillations modulated by auditory–motor tasks‐intracranial recording in patients with epilepsy

Human activities often involve hand‐motor responses following external auditory–verbal commands. It has been believed that hand movements are predominantly driven by the contralateral primary sensorimotor cortex, whereas auditory–verbal information is processed in both superior temporal gyri. It remains unknown whether cortical activation in the superior temporal gyrus during an auditory–motor task is affected by laterality of hand‐motor responses. Here, event‐related γ‐oscillations were intracranially recorded as quantitative measures of cortical activation; we determined how cortical structures were activated by auditory‐cued movement using each hand in 15 patients with focal epilepsy. Auditory–verbal stimuli elicited augmentation of γ‐oscillations in a posterior portion of the superior temporal gyrus, whereas hand‐motor responses elicited γ‐augmentation in the pre‐ and postcentral gyri. The magnitudes of such γ‐augmentation in the superior temporal, precentral, and postcentral gyri were significantly larger when the hand contralateral to the recorded hemisphere was required to be used for motor responses, compared with when the ipsilateral hand was. The superior temporal gyrus in each hemisphere might play a greater pivotal role when the contralateral hand needs to be used for motor responses, compared with when the ipsilateral hand does. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.     

Monaural 40-Hz auditory steady-state magnetic responses can be useful for identifying epileptic focus in mesial temporal lobe epilepsy

ObjectivePatients with mesial temporal lobe epilepsy (mTLE) often exhibit central auditory processing (CAP) dysfunction. Monaural 40-Hz auditory steady-state magnetic responses (ASSRs) were recorded to explore the pathophysiology of mTLE.MethodsEighteen left mTLE patients, 11 right mTLE patients and 16 healthy controls (HCs) were examined. Monaural clicks were presented at a rate of 40 Hz. Phase-locking factor (PLF) and power values were analyzed within bilateral Heschl’s gyri.ResultsMonaural 40-Hz ASSR demonstrated temporal frequency dynamics in both PLF and power data. Symmetrical hemispheric contralaterality was revealed in HCs. However, predominant contralaterality was absent in mTLE patients. Specifically, right mTLE patients exhibited a lack of contralaterality in response to left ear but not right ear stimulation, and vice versa in left mTLE patients.ConclusionThis is the first study to use monaural 40-Hz ASSR with unilateral mTLE patients to clarify the relationship between CAP and epileptic focus. CAP dysfunction was characterized by a lack of contralaterality corresponding to epileptic focus.SignificanceMonaural 40-Hz ASSR can provide useful information for localizing epileptic focus in mTLE patients.     

Spontaneous modulations of high-frequency cortical activity

ObjectiveWe clarified the clinical and mechanistic significance of physiological modulations of high-frequency broadband cortical activity associated with spontaneous saccadic eye movements during a resting state.MethodsWe studied 30 patients who underwent epilepsy surgery following extraoperative electrocorticography and electrooculography recordings. We determined whether high-gamma activity at 70–110 Hz preceding saccade onset would predict upcoming ocular behaviors. We assessed how accurately the model incorporating saccade-related high-gamma modulations would localize the primary visual cortex defined by electrical stimulation.ResultsThe dynamic atlas demonstrated transient high-gamma suppression in the striatal cortex before saccade onset and high-gamma augmentation subsequently involving the widespread posterior brain regions. More intense striatal high-gamma suppression predicted the upcoming saccade directed to the ipsilateral side and lasting longer in duration. The bagged-tree-ensemble model demonstrated that intense saccade-related high-gamma modulations localized the visual cortex with an accuracy of 95%.ConclusionsWe successfully animated the neural dynamics supporting saccadic suppression, a principal mechanism minimizing the perception of blurred vision during rapid eye movements. The primary visual cortex per se may prepare actively in advance for massive image motion expected during upcoming prolonged saccades.SignificanceMeasuring saccade-related electrocorticographic signals may help localize the visual cortex and avoid misperceiving physiological high-frequency activity as epileptogenic.     

Damage to left anterior temporal cortex predicts impairment of complex syntactic processing: A lesion‐symptom mapping study

Sentence processing problems form a common consequence of left‐hemisphere brain injury, in some patients to such an extent that their pattern of language performance is characterized as “agrammatic”. However, the location of left‐hemisphere damage that causes such problems remains controversial. It has been suggested that the critical site for syntactic processing is Broca's area of the frontal cortex or, alternatively, that a more widely distributed network is responsible for syntactic processing. The aim of this study was to identify brain regions that are required for successful sentence processing. Voxel‐based lesion‐symptom mapping (VLSM) was used to identify brain regions where injury predicted impaired sentence processing in 50 native speakers of Icelandic with left‐hemisphere stroke. Sentence processing was assessed by having individuals identify which picture corresponded to a verbally presented sentence. The VLSM analysis revealed that impaired sentence processing was best predicted by damage to a large left‐hemisphere temporo‐parieto‐occipital area. This is likely due to the multimodal nature of the sentence processing task, which involves auditory and visual analysis, as well as lexical and syntactic processing. Specifically impaired processing of noncanonical sentence types, when compared with canonical sentence processing, was associated with damage to the left‐hemisphere anterior superior and middle temporal gyri and the temporal pole. Anterior temporal cortex, therefore, appears to play a crucial role in syntactic processing, and patients with brain damage to this area are more likely to present with receptive agrammatism than patients in which anterior temporal cortex is spared. Hum Brain Mapp 34:2715–2723, 2013. © 2012 Wiley Periodicals, Inc.     

Hearing suppression induced by electrical stimulation of human auditory cortex

In the course of performing electrical stimulation functional mapping (ESFM) in neurosurgery patients, we identified three subjects who experienced hearing suppression during stimulation of sites within the superior temporal gyrus (STG). One of these patients had long standing tinnitus that affected both ears. In all subjects, auditory event related potentials (ERPs) were recorded from chronically implanted intracranial electrodes and the results were used to localize auditory cortical fields within the STG. Hearing suppression sites were identified within anterior lateral Heschl's gyrus (HG) and posterior lateral STG, in what may be auditory belt and parabelt fields. Cortical stimulation suppressed hearing in both ears, which persisted beyond the period of electrical stimulation. Subjects experienced other stimulation-evoked perceptions at some of these same sites, including symptoms of vestibular activation and alteration of audio-visual speech processing. In contrast, stimulation of presumed core auditory cortex within posterior medial HG evoked sound perceptions, or in one case an increase in tinnitus intensity, that affected the contralateral ear and did not persist beyond the period of stimulation. The current results confirm a rarely reported experimental observation, and correlate the cortical sites associated with hearing suppression with physiologically identified auditory cortical fields.     

Single-fiber electromyography-based diagnosis of CACNA1A mutation in children: A potential role of the electrodiagnosis in the era of whole exome sequencing

IntroductionA loss-of-function mutation in CACNA1A, which encodes P/Q-type Ca channels, causes various diseases. As most of the Ca channels at neuromuscular junctions are of the P/Q type, patients with loss-of-function CACNA1A mutations exhibit disturbed neuromuscular transmission. The associated jitters and blocking in such patients can be detected by single-fiber electromyography (SFEMG).CasesWe report two cases with different phenotypes, which were predicted to harbor loss-of-function mutations of CACNA1A, by using axonal stimulation SFEMG. One case involved a 2-year-old boy with episodic ataxia type 2. The other case involved a 7-year-old girl diagnosed with epileptic encephalopathy. SFEMG results revealed jitters and blocking in both cases. Moreover, whole exome sequencing (WES) revealed a heterozygous CACNA1A mutation, c.5251C>T, p.Arg1751Trp, in the former case and a novel de novo CACNA1A mutation, c.2122G>A, p.Val708Met, in the latter.ConclusionsOur cases indicate that SFEMG is a potentially useful diagnostic tool for patients with CACNA1A mutation, especially in pediatric cases where trio analysis is difficult or novel mutations are present.     

Transcortical sensory aphasia: Dissociation between naming and comprehension

Abstract

Although anomia in transcortical sensory aphasia (TSA) is usually described as a semantically based deficit (naming and recognition are equally affected), dissociations in naming performance have occasionally been reported. We report a two-part study: in Study 1 the pattern of preserved and impaired language abilities was examined in five patients with TSA and intact object naming; in Study 2 the neural mechanism(s) underlying preserved visual confrontation naming in TSA was examined. Demographic factors, severity of language deficits, lesion volume and location, and cerebral asymmetries of patients with TSA and intact naming (TSA-intact) (n = 6) were compared with those of patients with TSA and impaired naming (TSA-impaired) (n = 6), anomic aphasia (Anomia) (n = 6), and left hemisphere damage without aphasia (Control). The results of Study 1 revealed that all five patients had a relative preservation of oral production (spontaneous speech, repetition, naming and reading aloud), but impaired auditory and written (sentence-level) comprehension. Object/picture naming was significantly better than auditory comprehension of the same targets, and naming was also preserved in tactile and auditory (verbal definitions and non-verbal sounds) modalites, but written naming was impaired. In four patients oral reading showed a pattern of phonological dyslexia. The results of Study 2 failed to demonstrate significant differences between the groups with preserved naming (TSA-intact and control) and those with impaired naming (TSA-impaired and anomia) in non-language variables that might explain the selective preservation or impairment of naming. These results are discussed in terms of the functional and anatomical independence of the neural systems responsible for object naming and comprehension.     

Chasing language through the brain: Successive parallel networks

ObjectiveTo describe the spatio-temporal dynamics and interactions during linguistic and memory tasks.MethodsEvent-related electrocorticographic (ECoG) spectral patterns obtained during cognitive tasks from 26 epilepsy patients (aged: 9–60 y) were analyzed in order to examine the spatio-temporal patterns of activation of cortical language areas. ECoGs (1024 Hz/channel) were recorded from 1567 subdural electrodes and 510 depth electrodes chronically implanted over or within the frontal, parietal, occipital and/or temporal lobes as part of their surgical work-up for intractable seizures. Six language/memory tasks were performed, which required responding verbally to auditory or visual word stimuli. Detailed analysis of electrode locations allowed combining results across patients.ResultsTransient increases in induced ECoG gamma power (70–100 Hz) were observed in response to hearing words (central superior temporal gyrus), reading text and naming pictures (occipital and fusiform cortex) and speaking (pre-central, post-central and sub-central cortex).ConclusionsBetween these activations there was widespread spatial divergence followed by convergence of gamma activity that reliably identified cortical areas associated with task-specific processes.SignificanceThe combined dataset supports the concept of functionally-specific locally parallel language networks that are widely distributed, partially interacting in succession to serve the cognitive and behavioral demands of the tasks.     

Four-dimensional map of the human early visual system

Objective

We generated a large-scale, four-dimensional map of neuronal modulations elicited by full-field flash stimulation.

Broca's Area Damage is Necessary but not Sufficient to Induce After-effects of cathodal tDCS on the Unaffected Hemisphere in Post-stroke Aphasia

BackgroundThe inter-individual variability of behavioral effects after tDCS applied to the unaffected right hemisphere in stroke may be related to factors such as the lesion location.Objective/hypothesisWe investigated the effect of left Broca's area (BA) damage on picture naming in aphasic patients after cathodal tDCS applied over the right BA.MethodsWe conducted a study using pre-interventional diffusion and resting state functional MRI (rsfMRI) and two cross-over tDCS sessions (TYPE: sham and cathodal) over the right homologous BA in aphasic stroke patients with ischemic lesions involving the left BA (BA+) or other left brain areas (BA−). Picture naming accuracy was assessed after each session. Inter-hemispheric (IH) functional balance was investigated via rsfMRI connectivity maps using the right BA as a seed. Probabilistic tractography was used to study the integrity of language white matter pathways.ResultstDCS had different effects on picture naming accuracy in BA+ and BA− patients (TYPE × GROUP interaction, F(1,19): 4.6, P: 0.04). All BA− patients except one did not respond to tDCS and demonstrated normal IH balance between the right and left BA when compared to healthy subjects. BA+ patients were improved by tDCS in 36% and had decreased level of functional IH balance. Improvement in picture naming after cathodal tDCS was associated with the integrity of the arcuate fasciculus in BA+ patients.ConclusionsBehavioral effects of cathodal tDCS on the unaffected right hemisphere differ depending on whether BA and the arcuate fasciculus are damaged. Therefore, IH imbalance could be a direct consequence of anatomical lesions.     

Enhancing language performance with non-invasive brain stimulation--a transcranial direct current stimulation study in healthy humans

In humans, transcranial direct current stimulation (tDCS) can be used to induce, depending on polarity, increases or decreases of cortical excitability by polarization of the underlying brain tissue. Cognitive enhancement as a result of tDCS has been reported. The purpose of this study was to test whether weak tDCS (current density, 57 microA/cm(2)) can be used to modify language processing. Fifteen healthy subjects performed a visual picture naming task before, during and after tDCS applied over the posterior perisylvian region (PPR), i.e. an area which includes Wernicke's area [BA 22]. Four different sessions were carried out: (1) anodal and (2) cathodal stimulation of left PPR and, for control, (3) anodal stimulation of the homologous region of the right hemisphere and (4) sham stimulation. We found that subjects responded significantly faster following anodal tDCS to the left PPR (p<0.01). No decreases in performance were detected. Our finding of a transient improvement in a language task following the application of tDCS together with previous studies which investigated the modulation of picture naming latency by transcranial magnetic stimulation (TMS) and repetitive TMS (rTMS) suggest that tDCS applied to the left PPR (including Wernicke's area [BA 22]) can be used to enhance language processing in healthy subjects. Whether this safe, low cost, and easy to use brain stimulation technique can be used to ameliorate deficits of picture naming in aphasic patients needs further investigations.     

The pace of prosodic phrasing couples the listener's cortex to the reader's voice

We studied online coupling between a reader's voice and a listener's cortical activity using a novel, ecologically valid continuous listening paradigm. Whole‐scalp magnetoencephalographic (MEG) signals were recorded from 10 right‐handed, native French‐speaking listeners in four conditions: a female (Exp1f) and a male (Exp1m) reading the same text in French; a male reading a text in Finnish (Exp 2), a language incomprehensible for the subjects, and a male humming Exp1 text (Exp 3). The fundamental frequency (f0) of the reader's voice was recorded with an accelerometer attached to the throat, and coherence was computed between f0 time‐course and listener's MEG. Similar levels of right‐hemisphere‐predominant coherence were found at ?0.5 Hz in Exps 1–3. Dynamic imaging of coherent sources revealed that the most coherent brain regions were located in the right posterior superior temporal sulcus (pSTS) and posterior superior temporal gyrus (pSTG) in Exps 1–2 and in the right supratemporal auditory cortex in Exp 3. Comparison between speech rhythm and phrasing suggested a connection of the observed coherence to pauses at the sentence level both in the spoken and hummed text. These results demonstrate significant coupling at ～0.5 Hz between reader's voice and listener's cortical signals during listening to natural continuous voice. The observed coupling suggests that voice envelope fluctuations, due to prosodic rhythmicity at the phrasal and sentence levels, are reflected in the listener's cortex as rhythmicity of about 2‐s cycles. The predominance of the coherence in the right pSTS and pSTG suggests hemispherical asymmetry in processing of speech sounds at subsentence time scales. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.     

Contrasting treatments for severe impairments of picture naming

Abstract

Little is known about the treatment of object naming impairments in patients with multiple loci of deficit in the cognitive processes underlying picture naming. We evaluated the outcome of naming treatment in two such patients. We developed two treatments on the basis of a cognitive neuropsychological assessment of naming and contrasted their effectiveness with that of simple verbal rehearsal. In Treatment Programme 1, we targeted presumed impairment at the level of lexical retrieval by attempting to train subjects to use a phonological cueing hierarchy during a name to auditory definition task. In Treatment Programme 2, we targeted presumed impairment of visual-semantic processing by attempting to train subjects to use a visual-semantic cueing hierarchy during an oral picture naming task. Treatment Programme 3 was designed to determine if improvement in oral naming could result from simple rehearsal. All three treatment programmes improved naming abilities of the two subjects to some degree, particularly Treatment Programmes 1 and 2. We discuss various factors that may have contributed to these results. Although this report does not conclusively demonstrate efficacy of naming treatment in subjects with inordinate picture naming impairment due to multiple loci of disruption within the naming process, it suggests that cognitive processes implicated in this disorder are sensitive to these interventions.     

Multimodality language mapping in patients with left-hemispheric language dominance on Wada test

Objective

We determined the utility of electrocorticography (ECoG) and stimulation for detecting language-related sites in patients with left-hemispheric language-dominance on Wada test.

Methods

We studied 13 epileptic patients who underwent language mapping using event-related gamma-oscillations on ECoG and stimulation via subdural electrodes. Sites showing significant gamma-augmentation during an auditory-naming task were defined as language-related ECoG sites. Sites at which stimulation resulted in auditory perceptual changes, failure to verbalize a correct answer, or sensorimotor symptoms involving the mouth were defined as language-related stimulation sites. We determined how frequently these methods revealed language-related sites in the superior-temporal, inferior-frontal, dorsolateral-premotor, and inferior-Rolandic regions.

Results

Language-related sites in the superior-temporal and inferior-frontal gyri were detected by ECoG more frequently than stimulation (p < 0.05), while those in the dorsolateral-premotor and inferior-Rolandic regions were detected by both methods equally. Stimulation of language-related ECoG sites, compared to the others, more frequently elicited language symptoms (p < 0.00001). One patient developed dysphasia requiring in-patient speech therapy following resection of the dorsolateral-premotor and inferior-Rolandic regions containing language-related ECoG sites not otherwise detected by stimulation.

Conclusions

Language-related gamma-oscillations may serve as an alternative biomarker of underlying language function in patients with left-hemispheric language-dominance.

Significance

Measurement of language-related gamma-oscillations is warranted in presurgical evaluation of epileptic patients.