Biomedical subjects

Pascal Vianin

Publications and source records attributed to Pascal Vianin.

7 recordsLinked to original sources

PubMed2006

A first step toward cognitive remediation of voices: a case study.

Several studies have shown that source-monitoring errors are related to verbal hallucinations in schizophrenia. An exploratory pilot study has been carried out to investigate the possibility of training patients in how to avoid errors in source-monitoring. One patient with paranoid schizophrenia and persistent thought insertions was trained for 6 hours to use mnemonic techniques to compensate specific deficits in source-monitoring. Results show that the patient was able to improve his performance and maintain the acquired progress at a 1-month follow-up assessment. These preliminary results are interesting for developing a larger controlled study of cognitive remediation of source-monitoring deficits.

Adult↗

PubMed2005

Event-related potentials during rule processing in schizophrenia.

Several studies have shown that schizophrenia is characterized by impaired frontal lobe functions, functions that are responsible, for example, for the management of rules, strategic reasoning, and selective attention. Using event-related potentials (ERP), we assessed the brain's electrical activity in a group of patients with schizophrenia (n=11) and a healthy control group (n=14) during a reaction time task requiring the use of a rule. ERP waves were compared with those elicited in a similar task based on a direct sensory association. In the control group, ERP analyses showed a negative wave moving from the posterior to the anterior regions of the scalp in a latency range of 250-400 ms. Then, the negativity remained at the frontal scalp region in a latency range of 400-800 ms. In this group, the amplitude was higher during the rule operation than during the sensory association task. In schizophrenic patients, the anteroposterior component of the negative wave was totally absent in both tasks, and we did not find a modulation of the ERP by the task. Frontal scalp negativity was observed, but its latency was longer and its amplitude lower than in the control group. We discuss these findings in terms of the frontoposterior disconnection hypothesis.

Adult↗

PubMed2004

Distance estimation in a dynamic simulated environment: a visual field dependence problem?

Egocentric distance estimation implies that the subject perceives his own location in the environment. In a simulated environment, subjects have to transpose perceptively their own observation point in order to assume their virtual body position. As only visual information specifies this position, their ability to perceive the camera viewpoint should be linked to the field dependence independence factor (FDI). Field-independent subjects underestimated the mid-distance between their own virtual body position and a far-located target; their bisection was located between the projective (2-D) and the simulated (3-D) mid-distance which indicates their difficulty in considering the in-depth simulated spatial references. High correlations between the vertical estimation in the rod-and-frame test and the egocentric-distance-estimation task (with shifted camera) suggest a similar perceptive process in both tasks. This result is confirmed by the better performances of the field-dependent subjects in this condition. In conclusion, we discuss the relationship between FDI and the sense of presence in virtual environments.

Adult↗

PubMed2004

[Cognitive remediation: a new approach for treating schizophrenia].

Two years ago, the "E. Minkowski" section of the "Département Universitaire de Psychiatrie Adulte" in Lausanne (DUPA) developed a cognitive remediation program for young schizophrenic patients. Preliminary results indicate a significant improvement in cognitive performance in most patients. Despite encouraging results, cognitive remediation therapies for patients with schizophrenia are rarely used in our country. The importance of cognitive deficits contrasts with the lack of resources engaged for their remediation. Some hypotheses are discussed for understanding why the treatment of cognitive deficits in schizophrenia has been delayed.

Cognition Disorders↗

PubMed2003

Stimulus and response ERP analyses of a two-level reaction time task.

Higher cognitive processes include the ability to reliably transform sensory or mnemonic information. These processes either occur automatically or they are consciously controlled. To compare these two types of information processing, we developed a reaction time task that requires either a rule operation or else a direct sensory association. We were interested in evaluating the brain's electrical activity corresponding to both tasks, using event-related potentials (ERPs). In order to gain complete insight into the electrical activity of a stimulus-response segment, we analyzed the ERPs corresponding to the processing of the stimulus and the ERPs corresponding to the preparation of the response. To complete the analysis, we also evaluated the lateralized readiness potential (LRP) matched to the stimulus and to the response onset. Compared with the sensory association task, rule operation generated a higher negative potential field at frontocentral scalp areas in a latency range of 312-512 ms after the stimulus. In contrast, the LRP showed a negative component in the sensory association task which was absent during the rule operation; the latency of the difference was in the range 374-532 ms after the stimulus. The ERP component obtained by the response onset analysis was more negative in the rule condition up to a latency of -214 ms before the generation of the movement; the effect was localized at frontal and central scalp regions. We failed to find any significant difference in the LRP matched to the response onset. These results suggest that the brain computation of the rule operation takes place approximately in the middle of the stimulus-response time interval and that it is an additive process to the sensory association response.

Adult↗

PubMed2003

Augmentation of induced visual gamma activity by increased task complexity.

Recently the study of induced gamma band oscillations has focused on their modulation by top-down processes, mainly attention. Numerous studies have observed an increase in induced gamma band energy with increases in covert selective attention and visual perception. The current study investigated the modulation of visually induced gamma band oscillations by top-down processes associated with task complexity. Fourteen human subjects performed a reaction time task under two experimental conditions that differed in task complexity. In one, subjects simply had to press one of four buttons that corresponded to a colour stimulus shown to the subject. In the second, the stimulus response mapping was altered by the implementation of a rule, thus increasing task complexity. Cortical electrical activity was recorded using a 65 electrode whole scalp electroencephalographic (EEG) net. The EEG activity was analysed using Morlet wavelets to produce time-frequency maps. Although induced gamma band activity was observed in both conditions, there was significantly greater energy during the rule-operation condition at approximately 276 ms after the appearance of the stimulus. This increase was localized to electrodes overlying the right-central parietal scalp. The results of this study show that top-down processes modulate the level of induced gamma band activity. We discuss these findings in terms of the role of gamma oscillations in the construction of a sensory representation useful for a correct motor response.

Adolescent↗

PubMed2002

Reduced P300 amplitude in a visual recognition task in patients with schizophrenia.

We studied top-down visual processes in schizophrenia by analyzing visual event-related potentials (ERPs) during a gestalt recognition task, after subjects (patients with schizophrenia, n = 10; controls, n = 14) were trained to perceive three different geometrical shapes. Recognition performance of patients was poorer under both the figure and the nonfigure conditions then that of normal controls. ERPs analysis indicated that P300 amplitudes of the patients were significantly smaller than those of controls during correct figure detection trials. Moreover, topographical analysis of the differences in ERPs during the figure vs the nonfigure condition showed an earlier, more positive and more widely distributed P300 in controls than in patients with schizophrenia. Our study supports the misconnection hypothesis of schizophrenia and highlights the difficulty of the patients to refer to previous experience in order to filter incoming information. In a visual recognition task, this misconnection syndrome might induce a failure to integrate information stored in the frontal and prefrontal sites with incoming stimuli.

Adult↗