Dagmar Rachbauer | PubMed Health

PubMed2006

Differences in cerebral activation patterns in idiopathic inflammatory demyelination using the paced visual serial addition task: an fMRI study.

We performed a functional MRI (fMRI) study during the execution of the Paced Visual Serial Addition Task (PVSAT) in 9 patients with a clinically isolated syndrome suggestive of multiple sclerosis (CIS), 9 patients with clinically definite multiple sclerosis (CDMS), and 18 matched healthy control subjects. In controls, the PVSAT elicited a fronto-parietal network with cerebellar activation which we expected for this kind of working memory test and which indicates that this PVSAT version is an appropriate tool for measuring functional changes during a cognitive task. Although there were no significant differences in the actual test results of patients vs. controls, CDMS and CIS patients activated distinct cerebral networks in their attempt to solve the fMRI-PVSAT. Compared to CIS patients, CDMS patients showed increased hippocampal and parahippocampal activation, suggesting the need to additionally support their working memory. In contrast, compared to CDMS patients and healthy controls, CIS patients demonstrated stronger activation of the anterior cingulate cortex, which might indicate focused involvement of executive processes. On the PASAT (Paced Auditory Serial Addition Task) patients also performed similarly to controls but they showed decreased scores on most of the sub-tests of the Wechsler Memory Scale. Based on our observations using the fMRI-PVSAT, we hypothesize that distinct differences in cognitive processing occur with the evolution of MS and that, at these early stages of the disease, they cannot be detected with sufficient sensitivity using only the PASAT.

Adult↗

PubMedDate not supplied

Contextual and serial discriminations: a new learning paradigm to assess simultaneously the effects of acute stress on retrieval of flexible or stable information in mice.

The present study was aimed at simultaneously determining on the same subject, the effects of stress on retrieval of flexible (contextual or temporal) or stable (spatial) information. Three behavioral paradigms carried out in a four-hole board were designed as follows: (1) Simple Discrimination (SD), in which mice learned a single discrimination; (2) Contextual and Serial Discriminations (CSD), in which mice learned two successive discriminations on two different internal contexts; (3) Spatial Serial Discriminations (SSD), in which mice learned two successive discriminations on an identical internal context. The stressor (three inescapable electric footshocks) was delivered 5 min before retention, occurring 5 min or 24 h after acquisition. Results showed that this stressor increased plasmatic corticosterone levels and fear reactivity in an elevated-plus-maze, as compared with nonstressed mice. The stressor reversed the normal pattern of retrieval observed in nonstressed controls in the CSD task, this effect being context dependent, as it was not observed in the SSD task. Overall, our study shows that stress affected the retrieval of flexible and old information, but spared the retrieval of stable or recent ones. Therefore, these behavioral paradigms allow us to study simultaneously, on the same animal, the effects of stress on distinct forms of memory retrieval.

Acute Disease↗