Normalization of neuronal responses in cortical area MT across signal strengths and motion directions.
Normalization of neuronal responses in cortical area MT across signal strengths and motion directions.
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皮质区 MT 中神经元反应在信号强度和运动方向上的标准化。
DOI：
10.1152/jn.00700.2013
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发表时间：
2014
影响因子：
2.5
通讯作者：
Huang,Xin
中科院分区：
文献类型：
--
作者：
Xiao,Jianbo;Niu,Yu-Qiong;Wiesner,Steven;Huang,Xin
多种视觉刺激在自然场景中很常见，但目前尚不清楚多种刺激如何相互作用以影响神经元反应。我们通过操纵在纹状中颞叶皮层神经元的感受野（RF）内同时移动的两个刺激的相对信号强度来研究这个问题。视觉刺激是重叠的随机点图案，在相隔 90° 的两个方向上移动。我们首先改变每个随机点图案的运动相干性，并在方向调谐曲线上表征由双向刺激和组成运动分量引起的神经元反应之间的关系。双向刺激的调谐曲线显示出响应归一化，并且可以通过对运动分量的响应的加权和来解释。允许两个分量响应之间的非线性、乘性相互作用显着改善了某些神经元的数据拟合，并且这种相互作用主要对神经元响应具有抑制作用。分量响应的权重不是固定的，而是取决于相对信号强度。当两个刺激成分以不同的相干性水平移动时，较高相干性成分的响应权重显着大于较低相干性成分的响应权重。我们还改变了两个相干移动刺激的相对亮度水平，发现较高亮度分量的 MT 响应权重也更大。这些结果表明，神经元 RF 内多个刺激之间的竞争取决于刺激的相对信号强度，并且乘性非线性可能在塑造多个刺激的响应调谐方面发挥重要作用。
Multiple visual stimuli are common in natural scenes, yet it remains unclear how multiple stimuli interact to influence neuronal responses. We investigated this question by manipulating relative signal strengths of two stimuli moving simultaneously within the receptive fields (RFs) of neurons in the extrastriate middle temporal (MT) cortex. Visual stimuli were overlapping random-dot patterns moving in two directions separated by 90°. We first varied the motion coherence of each random-dot pattern and characterized, across the direction tuning curve, the relationship between neuronal responses elicited by bidirectional stimuli and by the constituent motion components. The tuning curve for bidirectional stimuli showed response normalization and can be accounted for by a weighted sum of the responses to the motion components. Allowing nonlinear, multiplicative interaction between the two component responses significantly improved the data fit for some neurons, and the interaction mainly had a suppressive effect on the neuronal response. The weighting of the component responses was not fixed but dependent on relative signal strengths. When two stimulus components moved at different coherence levels, the response weight for the higher-coherence component was significantly greater than that for the lower-coherence component. We also varied relative luminance levels of two coherently moving stimuli and found that MT response weight for the higher-luminance component was also greater. These results suggest that competition between multiple stimuli within a neuron's RF depends on relative signal strengths of the stimuli and that multiplicative nonlinearity may play an important role in shaping the response tuning for multiple stimuli.