This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.V1 projection zone signals in human macular degeneration depend on task, not stimulusThere is a controversy about the degree to which the adult visual cortex adapts following retinal damage. We describe functional magnetic resonance imaging (fMRI) experiments in four adult human subjects with juvenile macular degeneration (JMD). In all subjects, the foveal retina or macular retina is damaged creating a central retinal lesion. We measured the fMRI signals in visual cortex elicited by a variety of stimuli. The subjects either viewed the stimulus passively or performed a task. In all JMD subjects we observed stimulus-synchronized fMRI signals in the cortical projection zones of their intact retina. In three out of four JMD subjects, we observed additional stimulus-synchronized signals within the cortical projection zone of the lesioned retina (lesion projection zone, LPZ).The stimulus-synchronized signals in the LPZ were observed only when the JMD subjects performed an active short-term memory task; the LPZ did not respond during passive viewing or unrelated tasks. We mimicked the viewing conditions of the JMD subjects in healthy subjects and we did not observe any signals in the simulated LPZ using identical stimuli and tasks. We propose that the absence of retinal input unmasks cortico-cortical task-dependent signals. The cortico-cortical signals are normally silenced by geniculo-cortical signals specifying zero image contrast.AuthorYoichiro Masuda1,2, Serge O. Dumoulin1, Satoshi Nakadomari2, and Brian A. Wandell1 1. Psychology, Stanford University, Stanford, CA, USA 94305 2. Jikei University, School of Medicine, Tokyo, Japan
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