Biomedical subjects

J Bruno Debruille

Publications and source records attributed to J Bruno Debruille.

8 recordsLinked to original sources

PubMed2006

Delusions and processing of discrepant information: an event-related brain potential study.

One possible explanation for why delusions persist despite the awareness of contradictory information is that the new information fails to be integrated. Interestingly, the amplitude of the N400 event-related brain potential (ERP) has been proposed as an index of the integration of information that is discrepant with expectancies whatever the task in which the potential is found. Thus, delusions may persist because of a deficit in integration as indexed by the N400. To test this hypothesis, ERPs were recorded in 35 schizophrenia patients (mean age=30.5+/-5.6 years) and 26 normal controls during a task in which they either had to decide whether or not each target word could be integrated into the category "animal", or had no decision to make, according to the prompt "animal?" or the prompt "inaction". In these conditions, the amplitudes of the N400s to target words that were discrepant with the category were found to be negatively correlated with delusion severity. The patient group was then dichotomized according to a median split of delusion severity, excluding the 5 patients with delusion scores at the median. Mean age, sex ratio, and severity of conceptual disorganization and hallucinations of the two subgroups differed. Controlling for these 4 covariates, the N400s for discrepant targets were found smaller in the 14 More-Delusional patients than in the 16 Less-Delusional patients. These results support the hypothesis that delusions are associated with smaller N400s in patients. Further studies should thus be done to test whether a deficit of N400 processes could have a causal role in the persistence of delusions.

Adolescent↗

PubMed2006

Effect of connectivity and bistability on the visual potentials evoked by illusory figures.

The present study aimed at testing functional hypotheses regarding two brain potentials elicited by illusory figures. Accordingly, the N1 potential indexes mechanisms connecting the separate parts of the illusory form, whereas a subsequent negative potential indexes compensatory processes triggered by perceptual difficulty. Here, perceptual difficulty was induced by bistability; that is, by equating the probability of perceiving the illusory form to that of perceiving the independent separate parts. We compared the brain potentials evoked by a strongly connected illusory square, with almost no bistability, with those evoked by a weakly connected illusory square presenting strong bistability. Consistent with our hypotheses, the latter figure evoked the smallest N1 and a larger negative component peaking at 360 ms (N360). These results strengthen the link between N1 and connection and between negativity to perceptual difficulty and perceptual difficulty.

Adult↗

PubMed2005

The effect of interpolation and perceptual difficulty on the visual potentials evoked by illusory figures.

Completion is the process by which the brain unifies and segregates the parts of an incomplete form. It is qualified as amodal when the form is placed behind an obstacle and modal when the form is at the foreground and closed by illusory contours. The N1, and sometimes the N2, deflections of the visual evoked potentials are known to be larger for modal figures, such as the Kanizsa triangle, than for control figures. This result is generally linked to completion or illusory contours, but it could also be related to a third process: the interpolation of the form by connecting its separate parts. To test the influence of interpolation, a modal triangle, an amodal triangle, a figure with outlined inducers, and a no-triangle figure were randomly presented to 26 subjects. The N1 evoked by the three triangle figures were all larger than the N1 to the no-triangle figure. These results suggest that the N1 amplitude is largely determined by the possibility of interpolating a form in the figure. The greatest N1 to the modal figure further suggests that interpolation may be increased by modal completion and decreased by the features that diminish the saliency of triangle in the amodal figure and the figure with outlined inducers. On the other hand, the largest N2 was evoked by the amodal figure. This effect may index processes activated in response to the great difficulty in perceiving the triangle in the amodal figure, a difficulty that is initially caused by a conflict of perceptions characterizing this figure.

Adult↗

PubMed2005

The correlation between positive symptoms and left temporal event-related potentials in the P300 time window is auditory specific and training sensitive.

One of the strongest correlations found between clinical symptoms and a biological index is that between the severity of positive symptoms of schizophrenia and the amplitude of the event-related potential (ERP) in the time window of the P300 deflection at left temporal scalp sites. The functional significance of the ERP component at stake is yet unknown. The present study aims at addressing this issue by testing whether or not the correlation a) is found in both the auditory and the visual modality, b) is restricted to the time window of the P300 deflection, and c) is stable over time. 12 patients suffering from schizophrenia were recorded 6 times at two month intervals in two oddball protocols, an auditory and a visual one. The correlation between the scores for the thought disturbance cluster of the PANSS (a cluster including most positive symptoms, i.e., conceptual disorganization, unusual thought content, grandiosity and hallucinations) and the P300 amplitude at left temporal sites was found 1) to occur only in the auditory modality, which, together with the late timing of the component, constrains its functional significance, 2) to appear in a time window adjacent to that of the P300 including at additional electrode sites, which would have to be confirmed by further studies, 3) to vanish along with the repetition of the recording sessions, which suggests that it is related to a processing difficulty that disappears with training.

Acoustic Stimulation↗

PubMed2004

Semantics and N400: insights for schizophrenia.

Thought disorder is a hallmark symptom of schizophrenia, which often leads to deficits in social functioning. Some aspects of this cognitive dysfunction are the result of abnormal characteristics in the semantic processes of patients. These abnormalities exist not only at the discourse production level, but at the discourse comprehension level as well. The recording and analysis of event-related potentials has greatly advanced the investigation of the processing of linguistic information. One particular component of event-related potentials, N400, indexes semantic processing. Whereas all meaningful words elicit an N400, the amplitude of this component is much greater in response to words that are unexpected in a given context. As such, it is thought to reflect processes involved in contextual integration, which is the key to correct comprehension. N400 has been found to be abnormal in patients with schizophrenia when compared with healthy controls and, thus, may point toward the underlying cause of semantic deficits of patients with thought disorder.

Cognition Disorders↗

PubMed2003

The cognitive and anatomo-functional basis of reality distortion in schizophrenia: a view from memory event-related potentials.

This study investigated the neural and cognitive correlates of reality distortion in schizophrenia by using event-related potentials (ERPs) recorded in a recognition memory task for face. This task has been chosen because previous studies have shown that it provides distinct indices related to specific cognitive processes and to the functioning of specific brain regions. ERPs have been recorded in controls and schizophrenia patients separated into high scorers (RD+) and low-scorers (RD-) according to their Reality Distortion score (hallucination and delusion SAPS subscales). The results indicate that RD+ presents abnormalities on various cognitive processes. First, RD+ are deficient at interference inhibition and knowledge integration (reduced P2a and N400 effect). The similar impairments found in RD- suggest that they represent basic traits of the illness. Second, RD+ showed inappropriate stimulus categorization and contextual integration (larger N300 and fronto-central effect). Third, RD+ showed a late index (P600 effect) not different from controls, but larger than in RD-. This result is consistent with a qualitative, rather than quantitative, impairment of mnemonic binding processes (inappropriate binding) in RD+. Since each of the ERP abnormalities observed represents associated with distinct brain dysfunction, the results are further discussed in regard of the respective contribution of the parietal, frontal and hippocampal structures to reality distortion symptoms.

Adult↗

PubMed2003

Visual evoked potentials to line- and luminance-defined triangles.

Processing of line- and luminance-defined triangles was investigated by studying visual potentials (VEPs) evoked by triangles. Twenty-six subjects were randomly presented with line, grey, and illusory triangles. Relative to VEPs elicited by grey and illusory triangles, VEPs to line triangles included P220s that were smaller at frontal sites but larger at occipital sites, and N260s that were smaller over both temporal and occipital sites. It is proposed that, in contrast to triangle defined by a line, illusory and luminance-defined triangles include information involved in the processing of surface.

Adult↗

PubMed2002

The dimensional symptom structure of schizophrenia and its association with temperament and character.

Recent studies suggest that personality may influence symptom expression and social functioning in schizophrenia. This study investigated the relationships between personality and symptom dimensions in schizophrenia patients. Fifty-two schizophrenia patients and 25 five healthy subjects were assessed using the Temperament and Character Inventory (TCI). The patients were also assessed for positive and negative symptoms using SAPS and SANS and scored according to Andreasen's (1995: Andreasen, N.C., Arndt, S., Alliger, R., Miller, D., Flaum, M. 1995. Symptoms of schizophrenia. Methods, meanings, and mechanisms. Arch. Gen. Psychiatry, 52, 341-351) classical three dimensional model and by the five dimensional model of Toomey et al. (1997: Toomey, R., Kremen, W.S., Simpson J.C., Samson, J.A., Seidman, L.J., Lyons, M.J., Faraone, S.V., Tsuang, M.T. 1997. Revisiting the factor structure for positive and negative symptoms: evidence from a large heterogeneous group of psychiatric patients. Am. J. Psychiatry, 154, 371-377). Comparisons between patients and controls revealed significant differences on various TCI scores consistent with a global disorganization of personality in schizophrenia involving both basic neurophysiological and potentially genetically determined traits (i.e. temperament) and developmental aspects of personality (i.e. character). Correlation analysis showed distinct associations between symptoms and personality dimensions. The results suggest that the negative and disorganized dimensions of schizophrenia are related temperamental factors, whereas the psychotic symptoms are more related to characterological abnormalities. The observed patterns of associations also underline the heterogeneity of the classical negative and positive dimensions of schizophrenia.

Adult↗