Biomedical subjects

B Karoumi

Publications and source records attributed to B Karoumi.

5 recordsLinked to original sources

PubMed2001

Poor performance in smooth pursuit and antisaccadic eye-movement tasks in healthy siblings of patients with schizophrenia.

This study examines the area of eye movement dysfunctions as an indicator of vulnerability to schizophrenia. Eye movement performance was investigated with three different paradigms: Smooth Pursuit Eye Movements (SPEM); Visually Guided Saccades (VGS); and Antisaccades (AS) in 21 clinically stable patients with schizophrenia, 21 of their healthy, biological full siblings and 21 healthy control subjects. The three groups did not differ on VGS performance, whereas both patients and their siblings showed lower SPEM gain, an increased catch-up Saccades (CUS) rate, reduced AS accuracy and an increased number of AS errors in comparison to control subjects. In addition, patients with schizophrenia exhibited increased AS latency. Among the patients with schizophrenia, eye movement abnormalities did not correlate with age, gender, clinical state or duration of illness. These data suggest that abnormalities of SPEM and AS may represent neurobiological markers of the vulnerability to schizophrenia in individuals at high genetic risk for the disease.

Adult↗

PubMed2000

Alteration of event related potentials in siblings discordant for schizophrenia.

This study was aimed at confirming that auditory event related potential (ERP) abnormalities are indicators of vulnerability to schizophrenia. Auditory ERP performances were assessed at Fz, Cz, and Pz, with an oddball paradigm, in 21 clinically stable patients with schizophrenia, 21 of their healthy biological full siblings and 21 control subjects. The evoked response did not differ between the three groups on N200 waves. Compared to controls, patients with schizophrenia exhibited reduced amplitudes of N100 and P300, and prolonged latency of P300, while their siblings showed prolonged latency of P200 and P300. Among the patients with schizophrenia, ERP abnormalities did not correlate with age, clinical state, duration of illness or antipsychotic treatments. Although other conditions also accounted for alterations of the same type, ERP abnormalities may represent a neurobiological marker of the genetic vulnerability to schizophrenia, independent of phenotypic expression.

Adult↗

PubMed1998

Saccadic eye movements in schizophrenic patients.

The nature of saccadic abnormalities in schizophrenia was investigated in three different paradigms: (1) the visually guided saccade; (2) the antisaccade; and (3) the remembered saccade paradigm. Subjects comprised 14 schizophrenic patients and 14 normal volunteers. Deficits in the schizophrenic group were observed in the antisaccade and remembered saccade tasks, both of which were characterized by increased latency and reduced gain. Moreover, in the antisaccade task, schizophrenic patients showed an increased number of errors compared with control subjects. Saccadic abnormalities in the patients were correlated with impaired performance on the Wisconsin Card Sorting Test. These data suggest that schizophrenic patients have difficulty in inhibiting reflexive saccades and in producing voluntary saccades. The implications of these findings for a prefrontal cortex dysfunction involved in oculomotor control in schizophrenia are discussed.

Adult↗

PubMed1998

Predictive saccade behavior is enhanced in schizophrenia.

In this study, we investigated the ability of schizophrenic patients to produce predictive saccades in response to a visual target moving with predictable timing and location. The performance of visually guided saccades and predictive saccades (gain and latency) were analyzed in a group of 12 schizophrenic patients as compared with a group of ten control subjects. Our main finding was an enhancement of the predictive tracking ability in schizophrenics. In particular, the predictive tracking built-up and became installed as a steady pattern of highly anticipatory saccades (in terms of percentage of negative latency saccades) much faster in the schizophrenic group than in the control group. These data are discussed in terms of an involvement of the fronto-striatal system in this specific enhancement of predictive saccade behavior in schizophrenia.

Adult↗

PubMedDate not supplied

[Vulnerability to schizophrenia. II: Familial status of auditory evoked potential abnormalities].

The existence of a genetic background is well admitted in schizophrenia, but some individuals at genetic risk for that disease could never manifest it at a clinical level. However, several vulnerability models could help us to identify such individuals. According to them, when similar perturbations at a given task are observed both in clinically stable patients with schizophrenia and their nonschizophrenic first degree relatives, this task could be qualify as an indicator of the vulnerability to schizophrenia. In literature, that seems the case for auditory ERP late components in oddball paradigms. Our study was undertaken to replicate literature data. For that purpose, amplitude and latencies of auditory N100, P200, N200 and P300 wave-forms were assessed among 21 clinically, stable schizophrenics, 21 of their biological full siblings and 21 unrelated control subjects matched with the two others groups for several socio-demographic factors. Comparison were performed by non parametric analyses (Kruskal-Wallis one way ANOVA, and post-hoc Mann-Whitney). Compared to controls, delayed latencies and/or reduced amplitudes were observed for several ERP components--mainly with P300--in the sibling group. ERP values from this group did not statistically differ from those of the group with schizophrenia. In conclusion, results from the sibling group suggest that ERP impairments in auditory oddball paradigms may actually represent indicators of the genetic vulnerability to schizophrenia.

Adolescent↗