In vivo animation of auditory-language-induced gamma-oscillations in children with intractable focal epilepsy

Abstract

We determined if high-frequency gamma-oscillations (50- to 150-Hz) were induced by simple auditory communication over the language network areas in children with focal epilepsy. Four children (aged 7, 9, 10 and 16 years) with intractable left-hemispheric focal epilepsy underwent extraoperative electrocorticography (ECoG) as well as language mapping using neurostimulation and auditory-language-induced gamma-oscillations on ECoG. The audible communication was recorded concurrently and integrated with ECoG recording to allow for accurate time lock on ECoG analysis. In three children, who successfully completed the auditory-language task, high-frequency gamma-augmentation sequentially involved: i) the posterior superior temporal gyrus when listening to the question, ii) the posterior lateral temporal region and the posterior frontal region in the time interval between question completion and the patient's vocalization, and iii) the pre- and post-central gyri immediately preceding and during the patient's vocalization. The youngest child, with attention deficits, failed to cooperate during the auditory-language task, and high-frequency gamma-augmentation was noted only in the posterior superior temporal gyrus when audible questions were given. The size of language areas suggested by statistically significant high-frequency gamma-augmentation was larger than that defined by neurostimulation. The present method can provide in vivo imaging of electrophysiological activities over the language network areas during language processes. Further studies are warranted to determine whether recording of language-induced gamma-oscillations can supplement language mapping using neurostimulation in presurgical evaluation of children with focal epilepsy.

Scalp-Recorded Induced Gamma-Band Responses to Auditory Stimulation and Its Correlations with Saccadic Muscle-Activity

“…Reliable intracranial human and animal findings show that gamma-band activity is involved in auditory processing (Crone et al 2001;Lachaux et al 2007b;Lachaux et al 2007a;Brown et al 2008;Ray et al 2008;Towle et al 2008). Most intracranial findings show a broadband continuous gamma increase which onsets within 100 ms (Crone et al 2001) or even less (only a few miliseconds; Lachaux et al 2007a;Towle et al 2008) after stimulus presentation, and lasts for the duration of the stimulus or more (Trautner et al 2006).…”

Electrocorticographic Frequency Alteration Mapping for Extraoperative Localization of Speech Cortex

“…These high frequencies show an increase in amplitude in association with numerous motor, language, and cognitive tasks. [9][10][11][14][15][16] Gamma changes are thought to represent the cortical activity from smaller cortical assemblies of neurons involved in task performance. 13,17 Both low-and high-frequency amplitude changes have been shown to localize topographically over areas of active cortex.…”

“…13,17 Both low-and high-frequency amplitude changes have been shown to localize topographically over areas of active cortex. 8,9,11,14,15 Electrocorticography has been used to study the cortical physiology of motor and language function by multiple investigators. 8,9,11,14 Crone et al 11 showed mu and beta rhythms to have a reduced amplitude (termed event-related desynchronization) and gamma rhythms to have an increased amplitude with voluntary movement (termed event-related synchronization).…”

“…8,9,11,14,15 Electrocorticography has been used to study the cortical physiology of motor and language function by multiple investigators. 8,9,11,14 Crone et al 11 showed mu and beta rhythms to have a reduced amplitude (termed event-related desynchronization) and gamma rhythms to have an increased amplitude with voluntary movement (termed event-related synchronization). Crone et al 11 found changes associated with gamma activity to have a more localized topographic pattern and concluded that these rhythms were potentially more useful for mapping.…”

“…However, a recent study of auditory language in children showed the opposite effect: that gamma activation occurred over a larger area of cortex than that identified by ECS. 14 In the current study, the utility of EFAM for identification of language sites was investigated. Previously mentioned studies and others 18,19 indicate that different cortical areas are activated when different language modalities are used.…”