Damien Gabriel - Academia.edu (original) (raw)

Papers by Damien Gabriel

!e present study investigates the interaction between prosodic and lexical information in express... more !e present study investigates the interaction between prosodic and lexical information in expressing and recognising emotional states in the encoding and decoding of speech. !e study deals with the processing of interjections in English and is based on previous studies using German data (Dietrich et al., 2006), where it was found that listeners classify interjections into two categories with respect to lexical ambiguity. In the current investigation, behavioural data indicate that interjections can be classified into the two major categories: interjections with low or high lexical information. High lexical information has been demonstrated to facilitate recognition of emotion due to the redundancy in the prosodic and lexical information, e.g. yuk can only be classified as disgust. Items with low lexical content in contrast are ambiguous and may be used to express different emotions, e.g. a single–vowel like /a/ may express happiness, surprise, or anger. !e intended meaning and its c...

PLOS ONE, 2015

The ability to develop successful long-term strategies in uncertain situations relies on complex ... more The ability to develop successful long-term strategies in uncertain situations relies on complex neural mechanisms. Although lesion studies have shown some of the mechanisms involved, it is still unknown why some healthy subjects are able to make the right decision whereas others are not. The aim of our study was to investigate neurophysiological differences underlying this ability to develop a successful strategy in a group of healthy subjects playing a monetary card game called the Iowa Gambling Task (IGT). In this task, subjects have to win and earn money by choosing between four decks of cards, two were advantageous in the long term and two disadvantageous. Twenty healthy right-handed subjects performed the IGT while their cerebral activity was recorded by electroencephalography. Based on their behavioral performances, two groups of subjects could clearly be distinguished: one who selected the good decks and thus succeeded in developing a Favorable strategy (9 subjects) and one who remained Undecided (11 subjects). No neural difference was found between each group before the selection of a deck, but in both groups a greater negativity was found emerging from the right superior frontal gyrus 600 ms before a disadvantageous selection. During the processing of the feedback, an attenuation of the P200 and P300 waveforms was found for the Undecided group, and a P300 originating from the medial frontal gyrus was found in response to a loss only in the Favorable group. Our results suggest that undecided subjects are hyposensitive to the valence of the cards during gambling, which affects the feedback processing.

Neuroscience, 2015

Assessment of awareness in patients with disorders of consciousness such as patients in a vegetat... more Assessment of awareness in patients with disorders of consciousness such as patients in a vegetative state (unresponsive wakefulness syndrome, UWS) and patients in a minimally conscious state (MCS) remains difficult, with a high rate of misdiagnosis (around 40%). While patients with UWS have no awareness, patients with MCS have partial preservation of conscious awareness. To improve the assessment of awareness in these patients, recent functional neuroimaging protocols have been developed. However, does the complexity of realizing and interpreting these functional magnetic resonance imaging (fMRI) investigation protocols, which are currently carried out by only a few specialist teams, permit generalizable use in clinical routine? In this study, 32 healthy volunteers, by definition perfectly conscious and able to efficiently communicate, performed the protocol proposed by Monti et al. in 2010. Four methods (comprising the method proposed by Monti et al., a mean squared error-based method, a correlation-based method, and a support vector machine-based method) were tested for correctly and accurately interpreting the communication task. Firstly, the different instructions for the localizer and the communication tasks had no effect on activations. Secondly, 25% of participants (8/32) did not provide the expected patterns of activations during fMRI tasks (four for each imagery task). However, this did not necessarily prevent the classification methods from correctly guessing the answers during the communication task. Conversely, these classification methods may fail to detect the correct answers even though participants activated the expected brain areas. None of the four methods produced 100% correct detection during the communication phases. The correlation-based method obtained the best results with an error rate of 4.2%. The results of this study demonstrate that fMRI-based communication paradigms may not be robust enough to reliably detect awareness in all aware patients. There is still a need to develop new statistical and analytical methods before considering their generalization in clinical routine.

Frontiers in human neuroscience, 2015

Neuroscience, Jan 2, 2015

To improve the assessment of awareness in patients with disorders of consciousness, recent protoc... more To improve the assessment of awareness in patients with disorders of consciousness, recent protocols using functional Magnetic Resonance Imaging (fMRI) have been developed, and led some specialized coma centers to use this method on a routine basis. Recently, promising results have also been observed with electroencephalography (EEG), a less expensive and widely available technique. However, since the spatiotemporal nature of the recorded signal differs between both EEG and fMRI, the question of whether one method could substitute or should complement the other method is a matter of debate. In this study, we compared the neural processes of two well-known EEG and fMRI mental imagery protocols to define the relative place of each method in the assessment of awareness. A group of 20 healthy volunteers performed both EEG and fMRI command-following and communication tasks. Distinct command following was found with both EEG and fMRI for five subjects, only with fMRI for 12 subjects, and ...

Clinical EEG and Neuroscience, 2014

Recent studies have evidenced serious difficulties in detecting covert awareness with electroence... more Recent studies have evidenced serious difficulties in detecting covert awareness with electroencephalography-based techniques both in unresponsive patients and in healthy control subjects. This work reproduces the protocol design in two recent mental imagery studies with a larger group comprising 20 healthy volunteers. The main goal is assessing if modifications in the signal extraction techniques, training-testing/cross-validation routines, and hypotheses evoked in the statistical analysis, can provide solutions to the serious difficulties documented in the literature. The lack of robustness in the results advises for further search of alternative protocols more suitable for machine learning classification and of better performing signal treatment techniques. Specific recommendations are made using the findings in this work.

Plasticity and Signal Representation in the Auditory System, 2005

Overall results confirm the improvement in frequency discrimination performance around the cutoff... more Overall results confirm the improvement in frequency discrimination performance around the cutoff frequency in subjects with steeply sloping hearing loss. This effect does not appear to depend on the pattern of the hearing loss, as it can be observed in subjects with low-frequency, as well as notched hearing losses. Our findings, pointing to the steepness of the hearing loss and

Journal of Psycholinguistic Research, 2012

Several studies have shown that maintaining in memory some attributes of speech, such as the cont... more Several studies have shown that maintaining in memory some attributes of speech, such as the content or pitch of an interlocutor&amp;amp;amp;#39;s message, is markedly reduced in the presence of background sounds made of spectrotemporal variations. However, experimental paradigms showing this interference have only focused on one attribute of speech at a time, and thus differ from real-life situations in which several attributes have to be memorized and maintained simultaneously. It is possible that the interference is even greater in such a case and can occur for a broader range of background sounds. We developed a paradigm in which participants had to maintain the content, pitch and speaker size of auditorily presented speech information and used various auditory distractors to generate interference. We found that only distractors with spectrotemporal variations impaired the detection, which shows that similar interference mechanisms occur whether there are one or more speech attributes to maintain in memory. A high percentage of false alarms was observed with these distractors, suggesting that spectrotemporal variations not only weaken but also modify the information maintained in memory. Lastly, we found that participants were unaware of the interference. These results are similar to those observed in the visual modality.

International Journal of Audiology, 2006

The aim of the present study was to investigate the simple reaction time (RT) performance of pati... more The aim of the present study was to investigate the simple reaction time (RT) performance of patients with steeply sloping sensorineural hearing loss. This kind of hearing loss has the particularity of inducing a reorganization of the primary auditory cortex (Dietrich et al, 2001), the edge frequency of the loss being over-represented. It is assumed that a consequence of this plasticity could be reflected in an improvement in frequency discrimination performances around the edge of the loss (McDermott et al, 1998). In the present study we used pure tones equalized in loudness to investigate whether RT might be altered at the cut-off frequency (Fc) of the loss, or at the frequency that presented the best discrimination-limen-for-frequency (bDLF). The effect of auditory rehabilitation on RT was also studied. A great variability in RT was noted in all our subjects. Our results demonstrated that RT was unmodified at Fc or bDLF, be it before or after hearing aid fitting. However, an improvement in the correlation between RT and frequency discrimination performance was observed at three months post-rehabilitation.

Hearing Research, 2004

The aim of the present study was to investigate the functional organization of the auditory corte... more The aim of the present study was to investigate the functional organization of the auditory cortex for pure tones of 1, 2, 4, 6, 8 and 12 kHz. Ten subjects were tested with a whole-head magnetometer (151 channels). The location, latency and amplitude of the generators of the N1m (the main component of the response, peaking approximately at 100 ms) were explored simultaneously in the right and left hemispheres under monaural stimulation. Our results revealed that tonotopy is a rather complex functional organization of the auditory cortex. From 1 to 12 kHz, tonotopic maps were found for contralateral as well as for ipsilateral stimulation: N1m generators were found to be tonotopically organized mainly in an anterior-posterior direction in both hemispheres, whatever the stimulated ear, but also in an inferior-superior direction in the right hemisphere. Furthermore, latencies were longer in the left than in the right hemisphere. Two different representations of spectral distribution were found in the right auditory cortex: one for ipsilateral and one for contralateral stimulation.

Hearing Research, 2007

Cochlear damages have been shown to induce changes in tonotopic maps in the central auditory syst... more Cochlear damages have been shown to induce changes in tonotopic maps in the central auditory system of animals; neurons deprived from peripheral inputs start to respond to stimuli with frequencies close to the cutoff frequency (Fc) or ''edge'' of the hearing loss, which then become over-represented at the neural level. Here, we review findings, which reveal a possible psychophysical correlate of such central over-representation in human listeners with sensorineural hearing loss. These findings concur to demonstrate a local improvement in difference limens for frequency (DLFs) at or near Fc. This effect has now been observed in several studies and subjects with varied audiometric characteristics, including high-and low-frequency, and symmetric and asymmetric hearing losses. The presence of cochlear dead region or a steeply sloping hearing loss appear as a necessary condition for its occurrence. The effect cannot be explained simply by more prominent loudness cues or spontaneous otoacoustic emissions (SOAEs) near the audiogram edge. Overall, the data are consistent with local changes in pitch discrimination performance near the hearing-loss cutoff frequency being a result of the neural over-representation of that frequency region in the central auditory system. Further work is needed to confirm this hypothesis, and investigate other possible perceptual correlates of injury-related cortical plasticity in both humans and animals.

Hearing Research, 2006

Several studies have already demonstrated that patients with steeply sloping hearing loss of coch... more Several studies have already demonstrated that patients with steeply sloping hearing loss of cochlear origin exhibit an improvement in frequency discrimination performance at or around the cut-oV frequency. This enhancement cannot be explained in terms of peripheral mechanisms and should rather be interpreted in terms of central reorganization: i.e., injury-induced cortical plasticity. However, the reversibility and time course of such reorganization has not yet been described. The main goal of the present study was therefore to investigate the occurrence of rehabilitation plasticity associated with hearing-aid Wtting in human subjects. Nine subjects with steeply sloping hearing loss and who were candidates for auditory rehabilitation were tested. Discrimination-limen-for-frequency (DLF) enhancement was investigated at the frequency with the best DLF (bDLF) for each individual subject before and during auditory rehabilitation (at 1 month, 3 months and 6 months). From 1 month on, frequency discrimination performance decreased signiWcantly at the bDLF frequency, while remaining stable at other frequencies. This normalization may reXect a new central reorganization reversing the initial injury-induced changes in the cortical map. A correlation between subject's age and alteration in DLF at 1 month was also found, suggesting that plasticity operates faster in younger patients.

Brain Topography, 2014

The neural correlate of anterograde amnesia in Wernicke-Korsakoff syndrome (WKS) is still debated... more The neural correlate of anterograde amnesia in Wernicke-Korsakoff syndrome (WKS) is still debated. While the capacity to learn new information has been associated with integrity of the medial temporal lobe (MTL), previous studies indicated that the WKS is associated with diencephalic lesions, mainly in the mammillary bodies and anterior or dorsomedial thalamic nuclei. The present study tested the hypothesis that amnesia in WKS is associated with a disrupted neural circuit between diencephalic and hippocampal structures. High-density evoked potentials were recorded in four severely amnesic patients with chronic WKS, in five patients with chronic alcoholism without WKS, and in ten age matched controls. Participants performed a continuous recognition task of pictures previously shown to induce a left medial temporal lobe dependent positive potential between 250 and 350 ms. In addition, the integrity of the fornix was assessed using diffusion tensor imaging (DTI). WKS, but not alcoholic patients without WKS, showed absence of the early, left MTL dependent positive potential following immediate picture repetitions. DTI indicated disruption of the fornix, which connects diencephalic and hippocampal structures. The findings support an interpretation of anterograde amnesia in WKS as a consequence of a disconnection between diencephalic and MTL structures with deficient contribution of the MTL to rapid consolidation.

Cerebral Cortex, 2011

Memory verification is crucial for meaningful behavior. Orbitofrontal damage may impair verificat... more Memory verification is crucial for meaningful behavior. Orbitofrontal damage may impair verification and induce confabulation and inappropriate acts. The strategic retrieval account explains this state by deficient monitoring of memories&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; precise content, whereas the reality filter hypothesis explains it by a failure of an orbitofrontal mechanism suppressing the interference of memories that do not pertain to reality. The distinctiveness of these mechanisms has recently been questioned. Here, we juxtaposed these 2 mechanisms using high-resolution evoked potentials in healthy subjects who performed 2 runs of a continuous recognition task which contained pictures that precisely matched or only resembled previous pictures. We found behavioral and electrophysiological dissociation: Strategic content monitoring was maximally challenged by stimuli resembling previous ones, whereas reality filtering was maximally challenged by identical stimuli. Evoked potentials dissociated at 200-300 ms: Strategic monitoring induced a strong frontal negativity and a distinct cortical map configuration, which were particularly weakly expressed in reality filtering. Recognition of real repetitions was expressed at 300-400 ms, associated with ventromedial prefrontal activation. Thus, verification of a memory&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s concordance with the past (its content) dissociates from the verification of its concordance with the present. The role of these memory control mechanisms in the generation of confabulations and disorientation is discussed.

PLOS One, 2011

Acute lesions of the posterior medial orbitofrontal cortex (OFC) in humans may induce a state of ... more Acute lesions of the posterior medial orbitofrontal cortex (OFC) in humans may induce a state of reality confusion marked by confabulation, disorientation, and currently inappropriate actions. This clinical state is strongly associated with an inability to abandon previously valid anticipations, that is, extinction capacity. In healthy subjects, the filtering of memories according to their relation with ongoing reality is associated with activity in posterior medial OFC (area 13) and electrophysiologically expressed at 220-300 ms. These observations indicate that the human OFC also functions as a generic reality monitoring system. For this function, it is presumably more important for the OFC to evaluate the current behavioral appropriateness of anticipations rather than their hedonic value. In the present study, we put this hypothesis to the test. Participants performed a reversal learning task with intermittent absence of reward delivery. High-density evoked potential analysis showed that the omission of expected reward induced a specific electrocortical response in trials signaling the necessity to abandon the hitherto reward predicting choice, but not when omission of reward had no such connotation. This processing difference occurred at 200-300 ms. Source estimation using inverse solution analysis indicated that it emanated from the posterior medial OFC. We suggest that the human brain uses this signal from the OFC to keep thought and behavior in phase with reality.

Brain Topography, 2010

Little is known about how human amnesia affects the activation of cortical networks during memory... more Little is known about how human amnesia affects the activation of cortical networks during memory processing. In this study, we recorded high-density evoked potentials in 12 healthy control subjects and 11 amnesic patients with various types of brain damage affecting the medial temporal lobes, diencephalic structures, or both. Subjects performed a continuous recognition task composed of meaningful designs. Using whole-scalp spatiotemporal mapping techniques, we found that, during the first 200 ms following picture presentation, map configuration of amnesics and controls were indistinguishable. Beyond this period, processing significantly differed. Between 200 and 350 ms, amnesic patients expressed different topographical maps than controls in response to new and repeated pictures. From 350 to 550 ms, healthy subjects showed modulation of the same maps in response to new and repeated items. In amnesics, by contrast, presentation of repeated items induced different maps, indicating distinct cortical processing of new and old information. The study indicates that cortical mechanisms underlying memory formation and re-activation in amnesia fundamentally differ from normal memory processing.

Neuroscience, 2010

Dopamine has long held a prominent role in the interpretation of schizophrenia and other psychose... more Dopamine has long held a prominent role in the interpretation of schizophrenia and other psychoses. Clinical studies on confabulation and disorientation, disorders marked by a confusion of reality in thinking, indicated that the ability to keep thinking in phase with reality depends on a process suppressing the interference of upcoming memories that do not refer to ongoing reality. A host of animal studies and a recent clinical study suggested that this suppression might correspond to the phasic inhibition of dopaminergic neurons in response to the absence of expected outcomes. In this study, we tested healthy subjects with a difficult version of a memory paradigm on which confabulating patients had failed. Subjects participated in three test sessions, in which they received in double-blind, randomized fashion L-dopa, risperidone, or placebo. We found that Ldopa, in comparison with risperidone, impaired performance in a highly specific way, which corresponded to the pattern of patients with reality confusion. Specifically, they had an increase of false positive responses, while overall memory performance and reaction times were unaffected. We conclude that dopaminergic transmission influences the ability to rapidly adapt thinking to ongoing reality.

Hippocampus, 2010

Diverse studies demonstrated that although immediately repeated stimuli are better and faster rec... more Diverse studies demonstrated that although immediately repeated stimuli are better and faster recognized than stimuli repeated after a delay, this comes at the price of less-efficient long-term retention. A recent-evoked potential study using source estimation of high-resolution scalp EEG indicated that while immediate repetition induced a strikingly different electrical activity than new items in the left-medial temporal lobe (MTL) after 200–300 ms, delayed repetition did not. In this study, we recorded evoked potentials in two epileptic patients with intracranial depth electrodes in diverse temporal and frontal areas as they performed the same task as in the previous study. We found that immediate repetition induced increase of neural activity specifically in the left MTL between 250 and 400 ms compared to new items and items repeated after a delay. The findings are important in two ways. First, they support our previous conclusion that novel information immediately initiates a consolidation process involving the left-hippocampal area, which remains vulnerable during active maintenance and increases its effectiveness during off-line processing. Second, they indicate that source estimation based on high-resolution scalp EEG correctly localizes the current source of electrical activity in midline structures like the MTL. © 2010 Wiley-Liss, Inc.