A historical review of the representation of the visual field in primary visual cortex with special reference to the neural mechanisms underlying macular sparing

This article comprises a historical review of the literature pertaining to the representation of the visual field in human primary visual cortex. A brief survey of the anatomy of the visual system is followed by a critical evaluation of the key studies that have informed both the issue of the disproportionate representation of central vision within primary visual cortex, and the anatomical basis underlying the phenomena of macular sparing and macular splitting hemianopia.     

Foveal-to-peripheral priming in letter identification reflects response bias, not enhanced visibility

Several studies have suggested that it might be easier to identify a letter when its replication is simultaneously presented in the visual display. We have measured identification accuracy for a memorized target letter that was shown in the peripheral field in two conditions in which a letter either identical or different in shape was flashed simultaneously at fixation. The results of three forced-choice experiments showed that, contrary to Geiger and Lettvin's (1986) previous findings, an identity prime did not improve the visibility of a temporally backward masked target letter. However, the foveal prime letter could apparently bias the subject's decision so that he/she was much more ready to report the more visible prime letter as the peripheral target.     

利用反诱导消除McCollough效应

ＭｃＣｏｌｌｏｕｇｈ效应在完全黑暗和自然视觉条件下的消退过程很缓慢,而利用同频补色条栅来进行反诱导,能在十几分钟内消除显色效应。消除所用时间与反诱导条栅的亮度、颜色和栅条间距（空间频率）有关。进一步说明导致ＭｃＣｏｌｌｏｕｇｈ效应恢复平衡的主要因素跟网膜刺激方式有关。     

Visuomotor contribution to force variability in the plantarflexor and dorsiflexor muscles

The visual correction employed during isometric contractions of large proximal muscles contributes variability to the descending command and alters fluctuations in muscle force. This study explored the contribution of visuomotor correction to isometric force fluctuations for the more distal dorsiflexor (DF) and plantarflexor (PF) muscles of the ankle. Twenty-one healthy adults performed steady isometric contractions with the DF and PF muscles both with (VIS) and without (NOVIS) visual feedback of the force. The target forces exerted ranged from 2.5% to 80% MVC. The standard deviation (SD) and coefficient of variation (CV) of force was measured from the detrended (drift removed) VIS and NOVIS steadiness trials. Removal of VIS reduced the CV of force by 19% overall. The reduction in fluctuations without VIS was significant across a large range of target forces and was more consistent for the PF than the DF muscles. Thus, visuomotor correction contributes to the variability of force during isometric contractions of the ankle dorsiflexors and plantarflexors.     

Evaluation of the attentional capacities and working memory of early and late blind persons

Although attentional processes and working memory seem to be significantly involved in the daily activities (particularly during navigating) of persons who are blind and who use these abilities to compensate for their lack of vision, few studies have investigated these mechanisms in this population. The aim of this study is to evaluate the selective, sustained and divided attention, attentional inhibition and switching and working memory of blind persons. Early blind, late blind and sighted participants completed neuropsychological tests that were designed or adapted to be achievable in the absence of vision. The results revealed that the early blind participants outperformed the sighted ones in selective, sustained and divided attention and working memory tests, and the late blind participants outperformed the sighted participants in selective, sustained and divided attention. However, no differences were found between the blind groups and the sighted group in the attentional inhibition and switching tests. Furthermore, no differences were found between the early and late blind participants in this set of tests. These results suggest that early and late blind persons can compensate for the lack of vision by an enhancement of the attentional and working memory capacities.