Biomedical subjects

Stéphanie Dubal

Publications and source records attributed to Stéphanie Dubal.

4 recordsLinked to original sources

PubMed2006

Cognitive inhibition of number/length interference in a Piaget-like task in young adults: evidence from ERPs and fMRI.

We sought to determine whether the neural traces of a previous cognitive developmental stage could be evidenced in young adults. In order to do so, 12 young adults underwent two functional imaging acquisitions (EEG then fMRI). During each session, two experimental conditions were applied: a Piaget-like task with number/length interference (INT), and a reference task with number/length covariation (COV). To succeed at Piaget's numerical task, which children under the age of 7 years usually fail, the subjects had to inhibit a misleading strategy, namely, the visuospatial length-equals-number bias, a quantification heuristic that is often relevant and that continues to be used through adulthood. Behavioral data confirmed that although there was an automation in the young adult subjects as assessed by the very high number of accurate responses (>97%), the inhibition of the "length equals number strategy" had a cognitive cost, as the reaction times were significantly higher in INT than in COV (with a difference of 230 ms). The event-related potential results acquired during the first session showed electrophysiological markers of the cognitive inhibition of the number/length interference. Indeed, the frontal N2 was greater during INT than during COV, and a P3(late)/P6 was detected only during INT. During the fMRI session, a greater activation of unimodal areas (the right middle and superior occipital cortex) and in the ventral route (the left inferior temporal cortex) was observed in INT than in COV. These results seem to indicate that when fully automated in adults, inhibition processes might take place in unimodal areas.

Adult↗

PubMed2005

Intact hemispheric specialization for spatial and shape working memory in schizophrenia.

OBJECTIVE: Using functional MRI, we investigated whether, like healthy subjects, patients with schizophrenia show a relative hemispheric specialization in ventrolateral prefrontal cortex (PFC) for spatial and shape working memory (WM). We hypothesized that reduced specialization in schizophrenia would reflect a failure to adopt optimal domain-specific strategies and would contribute to WM deficits. METHODS: Twelve healthy subjects and 16 schizophrenia patients performed spatial and shape WM tasks and a non-WM control task. Direct comparisons of the spatial and shape WM tasks assessed specialization. RESULTS: Despite deficient WM performance, both patients and controls showed a relative hemispheric specialization in ventrolateral PFC for spatial (right) and shape (left) WM and did not differ in this regard. CONCLUSIONS: The finding of intact hemispheric specialization in ventrolateral PFC suggests that patients employ the same domain-specific strategies as healthy subjects during spatial and shape WM. Rather than reflecting a failure to adopt the optimal strategy, we hypothesize that WM deficits in schizophrenia reflect impairments of executive processes that are required for WM performance regardless of domain. These processes are associated with activity in the dorsolateral PFC, a region that has been repeatedly implicated in studies of WM.

Adult↗

PubMed2004

Time-on-task effect in trait anhedonia.

The capacity to sustain attention was explored in a sample of anhedonic subjects according to the Chapman physical anhedonia scale. Sustained attention was determined by studying task-induced changes over the duration of the Eriksen response competition task [Percept. Psychophys. 16 (1974) 143]. Anhedonic subjects had longer reaction times (RTs), but missed no more targets than control subjects. Anhedonic subject RTs got longer with time-on-task (TOT) and displayed greater intra-subject variability. These results confirm those of a previous study indicating that anhedonic subjects may have developed a more conservative response strategy [Psychophysiology 37 (2000) 711] and suggest that this strategy may result in a more rapid decrease in energetical resources. Moreover, the greater intra-subject variability demonstrates the importance of assessing performance over time and its relationship to the variability of responses in the cognitive performance of anhedonic subjects.

Adolescent↗

PubMed2004

Hemispheric specialization of the lateral prefrontal cortex for strategic processing during spatial and shape working memory.

OBJECTIVE: We investigated whether spatial working memory (WM) is associated with functional specialization of the right prefrontal cortex (PFC) relative to WM for shapes. We designed spatial and shape WM tasks that are relatively easy to perform and that minimize both task-switching and manipulation demands. The tasks use identical stimuli and require the same motor response. METHODS: We presented 12 subjects with target shapes that appeared in particular locations. Subjects maintained either the location or the shape of the targets in WM and responded to each probe by indicating whether it was a target. During a non-WM control task, subjects indicated whether the probe appeared on the right or left side of the screen. Subjects were scanned with a 3.0 T Siemens scanner and data were analyzed using SPM99. The WM tasks were compared to identify PFC activation that was different for spatial versus shape WM. Each WM task was also compared to the control task. RESULTS: compared with shape WM, spatial WM performance was faster and more accurate and was associated with increased right ventrolateral and frontopolar PFC activation. In contrast, compared to spatial WM, shape WM was associated with increased left ventrolateral PFC activity. CONCLUSIONS: These findings demonstrate hemispheric specialization for spatial versus shape WM in the ventrolateral PFC. The increased activity in the right PFC for spatial WM cannot be attributed to increased task difficulty, the stimuli used, or the response requirements. Rather, we propose that differences in performance and activation reflect the use of configural processing strategies for spatial WM.

Adult↗