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首页> 外文期刊>Journal of Neurophysiology >Normalization of neuronal responses in cortical area MT across signal strengths and motion directions
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Normalization of neuronal responses in cortical area MT across signal strengths and motion directions

机译：跨信号强度和运动方向对皮层MT中神经元反应的归一化

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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 neurons 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.
机译：多重视觉刺激在自然场景中很常见，但仍不清楚多重刺激如何相互作用以影响神经元反应。我们通过操纵在中上颞叶（MT）皮层中神经元的感受野（RFs）中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模式，在两个方向上移动了90？我们首先改变每个随机点模式的运动连贯性，并在整个方向调整曲线上表征双向刺激和运动成分所引起的神经元反应之间的关系。双向刺激的调谐曲线显示了响应归一化，可以通过对运动分量的响应的加权总和来解释。允许两个分量响应之间发生非线性，乘法交互作用，可以显着改善某些神经元的数据拟合，并且交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。当两个刺激分量以不同的连贯性水平移动时，较高连贯性分量的响应权重明显大于较低连贯性分量的响应权重。我们还改变了两个相干运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中多个刺激之间的竞争取决于刺激的相对信号强度，并且乘法非线性可能会在影响多个刺激的响应调整中起重要作用。

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