BACKGROUND AND PURPOSE: Plasticity in extended, parallel, or reciprocal operating networks is well recognized. Changes in neuronal activity after lesions to distinct localized structures, such as the primary visual cortex, are less well characterized. We investigated the cortical reorganization in patients with poststroke visual field defects using blood oxygen level-dependent functional MRI. METHODS: Brain activation was measured in 7 patients with a single occipital cortical lesion and partially recovered hemianopia and in 7 age-matched control subjects. Differences in activation between rest and visual hemifield stimulation were assessed with statistical parametric mapping (SPM'99). RESULTS: In normal subjects, significant activation was found in the contralateral primary visual cortex and bilaterally in the extrastriate cortex. During hemifield stimulation of the unaffected side of stroke patients, a similar pattern was found compared with that seen in control subjects. During stimulation of the hemianopic side, bilateral activation was seen within the extrastriate cortex, stronger in the ipsilateral hemisphere. The primary visual cortex was not significantly activated in either hemisphere during stimulation of the hemianopic side. CONCLUSIONS: Visual field defects after stroke are associated with bilateral activation of the extrastriate visual cortex. This pattern of activation indicates altered neuronal activity in the visual system. Further investigation is necessary to determine the relationship between functional reorganization and recovery of lost visual function after poststroke hemianopia.
BACKGROUND AND PURPOSE: Plasticity in extended, parallel, or reciprocal operating networks is well recognized. Changes in neuronal activity after lesions to distinct localized structures, such as the primary visual cortex, are less well characterized. We investigated the cortical reorganization in patients with poststroke visual field defects using blood oxygen level-dependent functional MRI. METHODS: Brain activation was measured in 7 patients with a single occipital cortical lesion and partially recovered hemianopia and in 7 age-matched control subjects. Differences in activation between rest and visual hemifield stimulation were assessed with statistical parametric mapping (SPM'99). RESULTS: In normal subjects, significant activation was found in the contralateral primary visual cortex and bilaterally in the extrastriate cortex. During hemifield stimulation of the unaffected side of strokepatients, a similar pattern was found compared with that seen in control subjects. During stimulation of the hemianopic side, bilateral activation was seen within the extrastriate cortex, stronger in the ipsilateral hemisphere. The primary visual cortex was not significantly activated in either hemisphere during stimulation of the hemianopic side. CONCLUSIONS:Visual field defects after stroke are associated with bilateral activation of the extrastriate visual cortex. This pattern of activation indicates altered neuronal activity in the visual system. Further investigation is necessary to determine the relationship between functional reorganization and recovery of lost visual function after poststroke hemianopia.
Authors: Gereon Nelles; Anja Pscherer; Armin de Greiff; Horst Gerhard; Michael Forsting; Joachim Esser; H Christoph Diener Journal: J Neurol Date: 2010-06-10 Impact factor: 4.849
Authors: Mohamed L Seghier; François Lazeyras; Slava Zimine; Sonja Saudan-Frei; Avinoam B Safran; Petra S Huppi Journal: BMC Neurol Date: 2005-09-26 Impact factor: 2.474
Authors: Gereon Nelles; Armin de Greiff; Anja Pscherer; Philipp Stude; Michael Forsting; Andreas Hufnagel; Horst Gerhard; Joachim Esser; H Christoph Diener Journal: J Neurol Date: 2007-08-11 Impact factor: 4.849
Authors: Gereon Nelles; Anja Pscherer; Armin de Greiff; Michael Forsting; Horst Gerhard; Joachim Esser; H Christoph Diener Journal: J Neurol Date: 2009-02-25 Impact factor: 4.849