Radial frequency tuning in human visual cortex
Radial frequency tuning in human visual cortex
复制标题
人类视觉皮层的径向频率调谐
DOI：
10.1167/17.10.293
复制
发表时间：
2017
影响因子：
1.8
通讯作者：
Morland A
中科院分区：
文献类型：
--
作者：
Morland A
径向频率（RF）模式是由圆半径的正弦调制定义的形状刺激。低频RF模式，周围的调制很少，由全球，中级形状机制处理，然而，这些机制在人类的神经轨迹还没有很好地理解。我们使用功能磁共振成像来测量神经反应的大范围的RF，并模拟神经调谐RF在早期，外侧和腹侧的视觉皮层。响应由在RF空间中定义的高斯神经模型建模，其中每个体素对RF的调谐由生成最佳预测fMRI数据的响应的模型定义。为了量化这种模式，我们测量了视觉区域V1，V2，V3，V4，VO1，VO2，LO1，LO2和对象选择性反射的RF调谐曲线。在所有受试者中，低的、全局处理的RF调谐定位于外侧枕叶皮质（LO）。具体来说，调整到全局RF首先出现在视野图LO1和LO2中，并持续到100。此外，我们将来自每个区域的RF调谐曲线与刺激对比能量和由圆形度定义的形状相关联。只有LO2和LO2曲线通过对形状的敏感性比对比能量更好地解释。所有的早期和腹侧地区调谐到高，局部处理的RF和更强烈的相关性与刺激对比能量的形状。我们使用控制刺激集复制了我们的结果，其中所有RF与相同的高频轮廓调制相结合，以匹配低水平差异的刺激，显示LO响应由低RF的全局形状驱动，其在两个刺激集之间保持恒定。我们的研究结果表明，通过外侧枕叶皮层，全球形状表征在LO2形成的形状处理途径，可能提供输入到大脑，在那里形成更复杂的对象表示。
Radial frequency (RF) patterns are shape stimuli defined by a sinusoidal modulation of a circle's radius. Low frequency RF patterns, with few modulations around the perimeter, are processed by global, mid-level shape mechanisms, however the neural locus of these mechanisms in humans is not well understood. We used fMRI to measure neural responses to a large range of RFs, and modeled neural tuning to RF in early, lateral and ventral visual cortex. Responses were modeled by a Gaussian neural model defined in RF space, where each voxel's tuning to RF was defined by the model which generated a response that best predicted the fMRI data. To quantify this pattern, we measured tuning profiles to RF for visual areas V1, V2, V3, V4, VO1, VO2, LO1, LO2 and object-selective LOC. Low, globally processed RF tuning was localised to lateral occipital cortex (LO) in all subjects. Specifically, tuning to global RFs first emerged in visual field maps LO1 and LO2, and persisted through LOC. In addition, we correlated RF tuning profiles from each area against stimulus contrast energy and shape defined by circularity. Only LO2 and LOC profiles were significantly better explained by sensitivity to shape over contrast energy. All early and ventral areas showed tuning to high, locally processed RFs and were more strongly correlated with stimulus contrast energy over shape. We replicated our results using a control stimulus set where all RFs were combined with the same high-frequency contour modulations to match stimuli for low-level differences, showing LO responses were driven by the global shape of low RFs which remained constant across both stimulus sets. Our results suggest a shape processing pathway through lateral occipital cortex, where global shape representations are formed in LO2, likely providing input to LOC where more complex representations of objects are formed.