Neurophysiologische Korrelate von Restwahrnehmung nach Läsion des primär visuellen Kortex

Zusammenfassung

Einleitung: In dieser Studie wurden die neurophysiologischen Korrelate der bewussten Restwahrnehmung für Bewegungsreize bei einem Patienten mit einer Läsion des primären Kortex nach einem Insult im Versorgungsgebiet der A. cerebri posterior untersucht. Methodik: Das durch Bewegungsreize im hemianopen Gesichtsfeld evozierte Aktivitätsmuster wurde mit Magnetenzephalographie und funktioneller Kernspintomographie untersucht. Ergebnisse: Die funktionelle Kernspintomographie zeigte, dass Bewegungsreize im hemianopen Gesichtsfeld Aktivierungen im extrastriären visuellen Kortex der geschädigten Hemisphäre hervorgerufen haben. Die Magnetenzephalographie zeigte, dass zunächst die hierarchisch höhere Region V5 und danach die hierarchisch niedrigeren Regionen V2/V3 in der Nähe der Läsion aktiviert wurden. Diskussion: Die Ergebnisse zeigen, dass Restwahrnehmung für Bewegung durch subkortikale Bahnen vermittelt werden kann, die den primär visuellen Kortex umgehen.

Abstract

Introduction: The neurophysiological correlates of preserved vision for motion associated with awareness were studied in a patient with a lesion of the striate cortex following a posterior cerebral artery stroke. Method: Magnetencephalography was employed in conjunction with functional magnetic resonance imaging to investigate the spatio-temporal pattern of neural activity elicited by moving stimuli presented to the hemianopic field of the patient. Results: Functional magnetic resonance imaging showed that motion stimuli presented to the hemianopic field produced activation in several extrastriate areas of the lesioned hemisphere. Magnetoencephalographic recordings indicated that evoked activity occurred earlier in the higher-tier visual area V5 than in the lower-tier areas V2/V3 adjacent to the lesion. Discussion: The results suggest that preserved vision for motion is mediated by subcortical pathways that bypass the primary visual cortex.

Key words

Riddoch syndrome - blindsight - PCA stroke - motion - MEG - fMRI

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