Amano Kaoru, Edwards Mark, Badcock David R, Nishida Shin'ya
NTT Communication Science Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
Vision Res. 2009 Nov;49(23):2862-9. doi: 10.1016/j.visres.2009.08.026. Epub 2009 Sep 2.
Cortical neurons that initially extract motion signals have small receptive-fields, and narrow orientation- and bandpass-spatial-frequency tuning. Accurate extraction of the veridical motion of objects typically requires the global pooling of the output of multiple local-motion units across orientation and space. We examined whether the narrow spatial-frequency tuning present at the local-motion level is preserved at the global-motion-pooling stage. Stimuli consisted of numerous drifting Gabor or plaid elements that were either signal (carrier drift-speed consistent with a given global-motion vector) or noise (drift speed consistent with a random, noise vector). The carrier spatial-frequencies of the signal and noise elements were independently varied. Regardless of the frequency of the signal elements, broad low-pass masking functions were obtained for both Gabor (one-dimensional) and Plaid (two-dimensional) conditions when measuring the threshold signal ratio for identification of the global-motion direction. For the Gabor stimuli, this pattern of results was also independent of the relative orientations of the signal and noise elements. These results indicate that in the global-motion pooling of one-dimensional and two-dimensional signals, local-motion signals of all spatial frequencies are pooled into a single system that exhibits broadband, low-pass tuning.
最初提取运动信号的皮层神经元具有小的感受野，以及狭窄的方向和带通空间频率调谐。准确提取物体的真实运动通常需要跨方向和空间对多个局部运动单元的输出进行全局汇总。我们研究了在局部运动水平上存在的狭窄空间频率调谐在全局运动汇总阶段是否得以保留。刺激由大量漂移的Gabor或方格元素组成，这些元素要么是信号（载波漂移速度与给定的全局运动矢量一致），要么是噪声（漂移速度与随机噪声矢量一致）。信号和噪声元素的载波空间频率是独立变化的。在测量用于识别全局运动方向的阈值信号比时，无论信号元素的频率如何，对于Gabor（一维）和方格（二维）条件，都获得了宽泛的低通掩蔽函数。对于Gabor刺激，这种结果模式也与信号和噪声元素的相对方向无关。这些结果表明，在一维和二维信号的全局运动汇总中，所有空间频率的局部运动信号都被汇总到一个表现出宽带、低通调谐的单一系统中。
