Biomedical subjects

François Guillem

Publications and source records attributed to François Guillem.

7 recordsLinked to original sources

PubMed2006

Use of the process dissociation procedure to study the contextual effects on face recognition in schizophrenia: familiarity, associative recollection and discriminative recollection.

Contextual effects were explored in schizophrenia patients and paired comparison subjects during a long-term face recognition task. The objective was to investigate the contextual effects on face recognition by manipulating, in the same experiment, the perceptual context of the face (intrinsic vs. extrinsic) and the task context (inclusion vs. exclusion instructions). The situation was derived from the Jacoby's [Jacoby, L.L., 1991. A process dissociation framework: separating automatic from intentional uses of memory. Journal of Memory and Language 30, 513-541] process dissociation procedure. The results showed that schizophrenia patients (N=20) presented lower performances than healthy controls (N=20) in the inclusion but not in the exclusion task. This observation emphasizes the heterogeneity of recollection and suggests that the memory impairment in schizophrenia reflects an imbalance between two mechanisms. The first is a deficit in "associative recollection", i.e., the failure to use efficiently associative information. The other is an enhanced "discriminative recollection" that impedes their capacity to process information separately from its perceptual context. In addition, correlation with symptoms suggest that the former is expressed in the loosening of associations characteristic of disorganization symptoms, whereas the latter reflects the lack of flexibility or the contextualization bias related to psychotic symptoms, i.e., delusions and hallucinations.

Adult↗

PubMed2005

The relationships between symptom dimensions and dysphoria in schizophrenia.

Previous studies have suggested that qualitatively distinct aspects of dysphoria (anxiety and depression) are related to specific dimension of schizophrenia symptomatology. Most of these studies used simple dimensions and dysphoria models, although finer distinctions could help defining specific relationships. This study examined the relationships of distinctive aspects of depression and anxiety (both state and trait) with symptom dimensions. Forty patients with a DSM-IV diagnosis of schizophrenia were assessed for symptoms (SAPS-SANS), trait and state anxiety (STAI) and depression (CDS). Symptoms ratings were summarized as dimensional scores according to a two-, three- or five-dimensional models proposed in the literature. The correlation analysis replicates previous observations that distinct aspects of dysphoria are associated with specific dimensions of schizophrenia, with the exception of disorganization. Moreover, controlling for intercorrelated variables revealed that schizophrenia and dysphoric symptoms might act in combination and/or through indirect links to contribute to illness expression. Our data further suggested that these associations may be best understood in terms of interactions between various processing biases alluded in the most recent cognitive accounts of schizophrenia symptoms.

Adult↗

PubMed2005

Are there common mechanisms in sensation seeking and reality distortion in schizophrenia? A study using memory event-related potentials.

A growing literature suggests that the characteristics of sensation seeking and reality distortion expressed in schizophrenia share several mechanisms. In a previous study, the comparison of patients with high vs. low reality distortion using event-related potentials (ERPs) recorded in a recognition memory task for unfamiliar faces identified neural and cognitive anomalies specifically related to the expression of these symptoms. As a follow-up, this study investigated the ERP correlates of sensation seeking in schizophrenia using the same recognition memory protocol. ERPs have been recorded in controls (N=21) and schizophrenia patients separated into high (HSS; N=13) and low (LSS; N=17) scorers according to Zuckerman's Sensation Seeking Scale. The results show a reduced P2a that was found unrelated to reality distortion in the previous study of reality distortion. It identifies interference inhibition impairment as being specifically related to sensation seeking. On the other hand, HSS scorers display enhanced fronto-central and normal P600 effects also found in high reality distortion patients. These results indicate inappropriate context processing and mnemonic binding common to sensation seeking and reality distortion. LSS scorers also display a reduced temporal N300 similar to that found in low reality distortion patients. This anomaly could reflect the lower reactivity to emotionally significant stimuli that underlies anhedonia symptoms. Finally, the N400 effect and a late frontal effect are found in both HSS and LSS. Since they were unrelated to reality distortion, these indices have been related to basic aspects of schizophrenia, e.g., deficient knowledge integration, or other mechanisms, e.g. anxiety or impulsivity. In summary, the present study examines the strategy of investigating variables, such as temperamental characteristics, in addition to symptoms, to show how discrete impairments may contribute to the expression of the illness.

Adult↗

PubMed2005

Gender differences in memory processing: evidence from event-related potentials to faces.

This study investigated gender differences on memory processing using event-related potentials (ERPs). Behavioral data and ERPs were recorded in 16 males and 10 females during a recognition memory task for faces. The behavioral data results showed that females performed better than males. Gender differences on ERPs were evidenced over anterior locations and involve the modulation of two spatially and temporally distinct components. These results are in general accordance with the view that males and females differ in the cognitive strategies they use to process information. Specifically, they could differ in their abilities to maintain information over interference and in the processing of the intrinsic contextual attributes of items, respectively, associated with the modulation of two anterior components. These interpretations lend support to the view that processing in females entails more detailed elaboration of information content than in males. Processing in males is more likely driven by schemas or overall information theme.

Adult↗

PubMed2005

Changes in the neuropsychological correlates of clinical dimensions between the acute and stable phase of schizophrenia.

This study was designed to investigate whether the neuropsychological correlates of the symptom dimensions of schizophrenia vary with the clinical state in patients followed from the acute to stable the phase of the illness. Fifteen patients were assessed for symptoms (SAPS-SANS) and undergone a complete neuropsychological assessment at two sessions. The first session (S1) was carried out within six days after admission, i.e., acute phase and the second (S2) at least two month after hospitalization, i.e., stable phase. The data were analyzed using stepwise regression models in which neuropsychological scores were in entered to predict each dimensional score. This analysis was applied on the S1 and S2 data as well as on the S2-S1 difference to assess the neuropsychological predictors of clinical changes. Generally, the results replicate the previous associations between neuropsychological and dimensional measures found in stable patients. In addition, this study shows if each dimension appears to rely on a key structure, symptom variations seems to involve changes in the spread of the dysfunction and/or changes in the connectivity between the key and other regions. The results also suggest that functional changes related to some symptoms dimensions occur to compensate for the dysfunction associated with other symptoms.

Acute Disease↗

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↗

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↗