Casile Antonino, Rucci Michele
Laboratory for Action Representation and Learning, Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University Clinic, 72072 Tübingen, Germany.
Neural Comput. 2006 Mar;18(3):569-90. doi: 10.1162/089976606775623270.
Under natural viewing conditions, the physiological instability of visual fixation keeps the projection of the stimulus on the retina in constant motion. After eye opening, chronic exposure to a constantly moving retinal image might influence the experience-dependent refinement of cell response characteristics. The results of previous modeling studies have suggested a contribution of fixational instability to the Hebbian maturation of the receptive fields of V1 simple cells (Rucci, Edelman, & Wray, 2000; Rucci & Casile, 2004). This letter examines the origins of such a contribution. Using quasilinear models of lateral geniculate nucleus units and V1 simple cells, we derive analytical expressions for the second-order statistics of thalamocortical activity before and after eye opening. We show that in the presence of natural stimulation, fixational instability introduces a spatially uncorrelated signal in the retinal input, which strongly influences the structure of correlated activity in the model. This input signal produces a regime of thalamocortical activity similar to that present before eye opening and compatible with the Hebbian maturation of cortical receptive fields.
在自然观察条件下，视觉注视的生理不稳定性使刺激在视网膜上的投影处于不断运动中。睁眼后，长期暴露于不断移动的视网膜图像可能会影响依赖经验的细胞反应特性的精细化。先前建模研究的结果表明，注视不稳定性对V1简单细胞感受野的赫布式成熟有贡献（鲁奇、埃德尔曼和雷，2000年；鲁奇和卡西莱，2004年）。本信函探讨了这种贡献的来源。使用外侧膝状体核单元和V1简单细胞的准线性模型，我们推导了睁眼前后丘脑皮质活动二阶统计量的解析表达式。我们表明，在自然刺激存在的情况下，注视不稳定性在视网膜输入中引入了空间不相关信号，这强烈影响了模型中相关活动的结构。这种输入信号产生了一种类似于睁眼之前的丘脑皮质活动状态，并与皮质感受野的赫布式成熟相一致。
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