Victor Vorobyev | PubMed Health

PubMed2006

Functional brain imaging, clinical and neurophysiological outcome of visual rehabilitation in a chronic stroke patient.

PURPOSE: To study rehabilitation outcome in a chronic visual field defect patient using positron emission tomography (PET) imaging, clinical, and neurophysiological measures. METHODS: A patient with chronic visual field defect was rehabilitated using a computer program over a three-month period. Evaluations of rehabilitation effects were done before and after training, and after a three-month follow-up with perimetry, visual evoked potentials (VEP), subjective questionnaire, and PET activation studies of regional cerebral blood flow (rCBF). RESULTS: In perimetry, the visual field increased during the training, and the patient also experienced subjective improvement. In VEP, a previously absent P100 component was identified after the training. In PET, increases in rCBF were diffuse immediately after the training, and more occipital after the late follow-up. A significant positive correlation between the increase in rCBF and improvement in clinical measures was found in the lingual gyrus in the contralesional hemisphere. CONCLUSIONS: All clinical measures showed improvement after rehabilitation, and this was maintained during the follow-up. In PET, a more generalized effect, found at the beginning, later concentrated in the occipital cortex. The results suggest that visual training may cause plastic changes in the brain, and that these changes can be detected both with clinical measures and with functional imaging.

Brain↗

PubMed2005

Naming of newly learned objects: a PET activation study.

The present study tracked the naming-related brain activity by positron emission tomography (PET) when successfully learned unfamiliar objects were named. Ten Finnish-speaking subjects participated in the study. Prior to the PET scan, each subject underwent a 4-day long training period in which 40 names of rare unfamiliar objects were taught. The stimulus categories were as follows: unfamiliar but real objects for which both the name and the definition were given during training, only the name was given, no information was given. In addition, familiar objects and visual noise patterns were used. The unfamiliar items mainly represented ancient domestic tools unknown to modern-day people. As semantic support did not affect the PET results, all trained items were pooled together. The trained objects vs. familiar objects contrast revealed rCBF increases in the left inferior frontal cortex (Broca's area), the left anterior temporal area, and the cerebellum. Likewise, the trained objects vs. unfamiliar objects (for which no information was given) contrast revealed more extensive left frontal (roughly Broca's area) and cerebellar rCBF increases, while anterior temporal activation was bilateral. Familiar objects, contrasted with both visual noise patterns and a rest condition, elicited activation increases in expected areas, i.e., bilateral occipital regions and the fusiform gyrus. Our results indicate that the naming of newly learned objects recruits more extensive brain areas than the naming of familiar items, namely a network that includes left-dominant frontotemporal areas and cerebellum. Its activity is tentatively related to enhanced lexical-semantic and lexical-phonological retrieval, as well as associative memory processes.

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