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Yoichiro Masuda, Hiroshi Horiguchi, Serge O. Dumoulin, Satoshi Nakadomari, Satoru Miyauchi, Shigeyuki Kan, Takahiko Koike, Ayumu Furuta, Hiroshi Tsuneoka, Brian A. Wandell; Population Receptive Field Estimates In Primary Visual Cortex Of Patients With Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4996.
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© ARVO (1962-2015); The Authors (2016-present)
BOLD responses can be elicited by task demands in regions of V1 deafferented due to retinal lesion. Our hypothesis is that task-dependent responses in the lesion projection zone (LPZ) arise from an imbalance between feed-forward gating signals and extrastriate feed-back signals (Masuda et al., 2008, 2010). Extrastriate feed-back neurons projecting to V1 have larger receptive fields (RF) than feed-forward signals. We used fMRI to measure the RF in the LPZ of retinitis pigmentosa (RP) patients and test the hypothesis that the RF size estimated from task-dependent LPZ signals is larger than the size estimated in corresponding V1 regions of healthy controls.
We measured RF size using moving-bar stimuli and a model-based analytical method (Dumoulin and Wandell, 2008). The subjects either viewed the stimuli passively or performed a stimulus judgment task. RP subjects had a peripheral visual field loss so that they had a visual field contraction within 10 degrees in radius. Control subjects were presented stimuli that simulated the peripheral visual field loss of the RP subject.
In all subjects during passive view we measured a response in the posterior calcarine sulcus, which is the functional retina projection zone (FPZ), and a large unresponsive zone in the anterior calcarine sulcus (LPZ). In control subjects there was no significant difference in the V1 signal between passive viewing and an attention-demanding task. However, in the RP subjects we observed a significant response in the LPZ in the attention-demanding task. The RF size estimated from the task-dependent BOLD was substantially larger than the typical RF size in this portion of anterior calcarine cortex.
The large RF size in the LPZ is consistent with the hypothesis that the task-dependent signals arise from extrastriate signals. We propose that in RP subjects, unlike controls, extrastriate feed-back signals are not gated by feed-forward retinal signals.
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