Inter-individual variability in dorsal stream dynamics during word production.

The current standard model of language production involves a sensorimotor dorsal stream connecting areas in the temporo-parietal junction with those in the inferior frontal gyrus and lateral premotor cortex. These regions have been linked to various aspects of word production such as phonological processing or articulatory programming, primarily through neuropsychological and functional imaging group studies. Most if not all the theoretical descriptions of this model imply that the same network should be identifiable across individual speakers.

An open-source toolbox for Multi-patient Intracranial EEG Analysis (MIA).

Intracranial EEG (iEEG) performed during the pre-surgical evaluation of refractory epilepsy provides a great opportunity to investigate the neurophysiology of human cognitive functions with exceptional spatial and temporal precisions. A difficulty of the iEEG approach for cognitive neuroscience, however, is the potential variability across patients in the anatomical location of implantations and in the functional responses therein recorded. In this context, we designed, implemented, and tested a user-friendly and efficient open-source toolbox for Multi-Patient Intracranial data Analysis (MIA), which can be used as standalone program or as a Brainstorm plugin.

What déjà vu and the "dreamy state" tell us about episodic memory networks.

Illusions of inappropriate familiarity with the current experience or hallucinatory recall of memories are reported in temporal lobe seizures. Pathophysiological hypotheses have been proposed, involving temporal limbic regions (Hughlings-Jackson), temporal neocortex ("interpretive cortex", Penfield), or both (Bancaud). Recent data acquired from presurgical investigations using intracerebral electrode recordings, demonstrate a critical role for the sub- and para-hippocampal cortices.

Functional Topography of Auditory Areas Derived From the Combination of Electrophysiological Recordings and Cortical Electrical Stimulation.

The posterior part of the superior temporal gyrus (STG) has long been known to be a crucial hub for auditory and language processing, at the crossroad of the functionally defined ventral and dorsal pathways. Anatomical studies have shown that this "auditory cortex" is composed of several cytoarchitectonic areas whose limits do not consistently match macro-anatomic landmarks like gyral and sulcal borders. The only method to record and accurately distinguish neuronal activity from the different auditory sub-fields of primary auditory cortex, located in the tip of Heschl and deeply buried in the Sylvian fissure, is to use stereotaxically implanted depth electrodes (Stereo-EEG) for pre-surgical evaluation of patients with epilepsy.

Contributions of electrophysiology for identifying cortical language systems in patients with epilepsy.

A crucial element of the surgical treatment of medically refractory epilepsy is to delineate cortical areas that must be spared in order to avoid clinically relevant neurological and neuropsychological deficits postoperatively. For each patient, this typically necessitates determining the language lateralization between hemispheres and language localization within hemisphere. Understanding cortical language systems is complicated by two primary challenges: the extent of the neural tissue involved and the substantial variability across individuals, especially in pathological populations.

Converging intracortical signatures of two separated processing timescales in human early auditory cortex.

Neural oscillations in auditory cortex are argued to support parsing and representing speech constituents at their corresponding temporal scales. Yet, how incoming sensory information interacts with ongoing spontaneous brain activity, what features of the neuronal microcircuitry underlie spontaneous and stimulus-evoked spectral fingerprints, and what these fingerprints entail for stimulus encoding, remain largely open questions. We used a combination of human invasive electrophysiology, computational modeling and decoding techniques to assess the information encoding properties of brain activity and to relate them to a plausible underlying neuronal microarchitecture.

Asymmetric sampling in human auditory cortex reveals spectral processing hierarchy.

Speech perception is mediated by both left and right auditory cortices but with differential sensitivity to specific acoustic information contained in the speech signal. A detailed description of this functional asymmetry is missing, and the underlying models are widely debated. We analyzed cortical responses from 96 epilepsy patients with electrode implantation in left or right primary, secondary, and/or association auditory cortex (AAC).

Neural processes of auditory perception in Heschl's gyrus for upcoming acoustic stimuli in humans.

In the natural environment, attended sounds tend to be perceived much better than unattended sounds. However, the physiological mechanism of how our neural systems direct the state of perceptual attention to prepare for the detection of upcoming acoustic stimuli before auditory stream segregation remains elusive. In this study, based on the direct intracerebral recordings from the auditory cortex in eight epileptic patients with refractory focal seizures, we investigated the neural processing of auditory attention by comparing the local field potentials before 'attentional' and 'distracted' conditions.

Cortical Dynamics of Semantic Priming and Interference during Word Production: An Intracerebral Study.

Language production requires that semantic representations are mapped to lexical representations on the basis of the ongoing context to select the appropriate words. This mapping is thought to generate two opposing phenomena, "semantic priming," where multiple word candidates are activated, and "interference," where these word activities are differentiated to make a goal-relevant selection. In previous neuroimaging and neurophysiological research, priming and interference have been associated to activity in regions of a left frontotemporal network.

An intracerebral exploration of functional connectivity during word production.

Language is mediated by pathways connecting distant brain regions that have diverse functional roles. For word production, the network includes a ventral pathway, connecting temporal and inferior frontal regions, and a dorsal pathway, connecting parietal and frontal regions. Despite the importance of word production for scientific and clinical purposes, the functional connectivity underlying this task has received relatively limited attention, and mostly from techniques limited in either spatial or temporal resolution.

The different patterns of seizure-induced aphasia in temporal lobe epilepsies.

Objectives: Ictal language disturbances may occur in dominant hemisphere temporal lobe epilepsy (TLE), but little is known about the precise anatomoelectroclinical correlations. This study investigated the different facets of ictal aphasia in intracerebrally recorded TLE.

Methods: Video-stereoelectroencephalography (SEEG) recordings of 37 seizures in 17 right-handed patients with drug-resistant TLE were analyzed; SEEG electroclinical correlations between language disturbance and involvement of temporal lobe structures were assessed.

The Role of Associative Cortices and Hippocampus during Movement Perturbations.

Although motor control has been extensively studied, most research involving neural recordings has focused on primary motor cortex, pre-motor cortex, supplementary motor area, and cerebellum. These regions are involved during normal movements, however, associative cortices and hippocampus are also likely involved during perturbed movements as one must detect the unexpected disturbance, inhibit the previous motor plan, and create a new plan to compensate. Minimal data is available on these brain regions during such "robust" movements.

Estimating Parallel Processing in a Language Task Using Single-Trial Intracerebral Electroencephalography.

We provide a quantitative assessment of the parallel-processing hypothesis included in various language-processing models. First, we highlight the importance of reasoning about cognitive processing at the level of single trials rather than using averages. Then, we report the results of an experiment in which the hypothesis was tested at an unprecedented level of granularity with intracerebral data recorded during a picture-naming task.

Hippocampus duality: Memory and novelty detection are subserved by distinct mechanisms.

The hippocampus plays a pivotal role both in novelty detection and in long-term memory. The physiological mechanisms underlying these behaviors have yet to be understood in humans. We recorded intracerebral evoked potentials within the hippocampus of epileptic patients (n = 10) during both memory and novelty detection tasks (targets in oddball tasks).

How functional coupling between the auditory cortex and the amygdala induces musical emotion: a single case study.

Music is a sound structure of remarkable acoustical and temporal complexity. Although it cannot denote specific meaning, it is one of the most potent and universal stimuli for inducing mood. How the auditory and limbic systems interact, and whether this interaction is lateralized when feeling emotions related to music, remains unclear.

High frequency gamma activity in the left hippocampus predicts visual object naming performance.

Access to an object's name requires the retrieval of an arbitrary association between it's identity and a word-label. The hippocampus is essential in retrieving arbitrary associations, and thus could be involved in retrieving the link between an object and its name. To test this hypothesis we recorded the iEEG signal from epileptic patients, directly implanted in the hippocampus, while they performed a picture naming task.

Single-trial EEG-informed fMRI reveals spatial dependency of BOLD signal on early and late IC-ERP amplitudes during face recognition.

Simultaneous EEG-fMRI has opened up new avenues for improving the spatio-temporal resolution of functional brain studies. However, this method usually suffers from poor EEG quality, especially for evoked potentials (ERPs), due to specific artifacts. As such, the use of EEG-informed fMRI analysis in the context of cognitive studies has particularly focused on optimizing narrow ERP time windows of interest, which ignores the rich diverse temporal information of the EEG signal.

Simultaneous recording of MEG, EEG and intracerebral EEG during visual stimulation: from feasibility to single-trial analysis.

Electroencephalography (EEG), magnetoencephalography (MEG), and intracerebral stereotaxic EEG (SEEG) are the three neurophysiological recording techniques, which are thought to capture the same type of brain activity. Still, the relationships between non-invasive (EEG, MEG) and invasive (SEEG) signals remain to be further investigated. In early attempts at comparing SEEG with either EEG or MEG, the recordings were performed separately for each modality.

How familiarization and repetition modulate the picture naming network.

A common strategy to reveal the components of the speech production network is to use psycholinguistic manipulations previously tested in behavioral protocols. This often disregards how implementation aspects that are nonessential for interpreting behavior may affect the neural response. We compared the electrophysiological (EEG) signature of two popular picture naming protocols involving either unfamiliar pictures without repetitions or repeated familiar pictures.

Action monitoring and medial frontal cortex: leading role of supplementary motor area.

The capacity to evaluate the outcomes of our actions is fundamental for adapting and optimizing behavior and depends on an action-monitoring system that assesses ongoing actions and detects errors. The neuronal network underlying this executive function, classically attributed to the rostral cingulate zone, is poorly characterized in humans, owing to the limited number of direct neurophysiological data. Using intracerebral recordings, we show that the leading role is played by the supplementary motor area (SMA), which rapidly evaluates successful and erroneous actions.

Ventral and dorsal pathways of speech perception: an intracerebral ERP study.

Recent theory of physiology of language suggests a dual stream dorsal/ventral organization of speech perception. Using intra-cerebral Event-related potentials (ERPs) during pre-surgical assessment of twelve drug-resistant epileptic patients, we aimed to single out electrophysiological patterns during both lexical-semantic and phonological monitoring tasks involving ventral and dorsal regions respectively. Phonological information processing predominantly occurred in the left supra-marginal gyrus (dorsal stream) and lexico-semantic information occurred in anterior/middle temporal and fusiform gyri (ventral stream).

Emotion processing in words: a test of the neural re-use hypothesis using surface and intracranial EEG.

This study investigates the spatiotemporal brain dynamics of emotional information processing during reading using a combination of surface and intracranial electroencephalography (EEG). Two different theoretical views were opposed. According to the standard psycholinguistic perspective, emotional responses to words are generated within the reading network itself subsequent to semantic activation.

Asymmetric function of theta and gamma activity in syllable processing: an intra-cortical study.

Low-gamma (25-45 Hz) and theta (4-8 Hz) oscillations are proposed to underpin the integration of phonemic and syllabic information, respectively. How these two scales of analysis split functions across hemispheres is unclear. We analyzed cortical responses from an epileptic patient with a rare bilateral electrode implantation (stereotactic EEG) in primary (A1/BA41 and A2/BA42) and association auditory cortices (BA22).

Intra-cranial recordings of brain activity during language production.

Recent findings in the neurophysiology of language production have provided a detailed description of the brain network underlying this behavior, as well as some indications about the timing of operations. Despite their invaluable utility, these data generally suffer from limitations either in terms of temporal resolution, or in terms of spatial localization. In addition, studying the neural basis of speech is complicated by the presence of articulation artifacts such as electro-myographic activity that interferes with the neural signal.

Hyperactivation of parahippocampal region and fusiform gyrus associated with successful encoding in medial temporal lobe epilepsy.

Purpose: Performance in recognition memory differs among patients with medial temporal lobe epilepsy (MTLE). We aimed to determine if distinct recognition performances (normal vs. impaired) could be related to distinct patterns of brain activation during encoding.