Cassanello Carlos R, Ferrera Vincent P
Columbia University, Department of Psychiatry, Center for Neurobiology and Behavior, David Mahoney Center for Brain and Behavior Research, New York, NY, USA.
Neural Comput. 2007 Sep;19(9):2353-86. doi: 10.1162/neco.2007.19.9.2353.
Saccadic eye movements remain spatially accurate even when the target becomes invisible and the initial eye position is perturbed. The brain accomplishes this in part by remapping the remembered target location in retinal coordinates. The computation that underlies this visual remapping is approximated by vector subtraction: the original saccade vector is updated by subtracting the vector corresponding to the intervening eye movement. The neural mechanism by which vector subtraction is implemented is not fully understood. Here, we investigate vector subtraction within a framework in which eye position and retinal target position signals interact multiplicatively (gain field). When the eyes move, they induce a spatial modulation of the firing rates across a retinotopic map of neurons. The updated saccade metric can be read from the shift of the peak of the population activity across the map. This model uses a quasi-linear (half-rectified) dependence on the eye position and requires the slope of the eye position input to be negatively proportional to the preferred retinal position of each neuron. We derive analytically this constraint and study its range of validity. We discuss how this mechanism relates to experimental results reported in the frontal eye fields of macaque monkeys.
即使目标变得不可见且初始眼位受到干扰，扫视眼动在空间上仍保持精确。大脑部分通过在视网膜坐标中重新映射记忆中的目标位置来实现这一点。这种视觉重新映射背后的计算可通过向量减法近似：原始扫视向量通过减去与中间眼动对应的向量来更新。实现向量减法的神经机制尚未完全理解。在这里，我们在眼位和视网膜目标位置信号以乘法方式相互作用（增益场）的框架内研究向量减法。当眼睛移动时，它们会在神经元的视网膜拓扑图上诱导放电率的空间调制。更新后的扫视度量可以从群体活动峰值在图上的移动中读取。该模型对眼位采用准线性（半整流）依赖，并且要求眼位输入的斜率与每个神经元的偏好视网膜位置成负比例。我们通过分析得出这个约束并研究其有效性范围。我们讨论这种机制与猕猴额叶眼区报道的实验结果有何关系。
