Becker Hubertus G T, Erb Michael, Haarmeier Thomas
Department of General Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
Eur J Neurosci. 2008 Oct;28(8):1674-85. doi: 10.1111/j.1460-9568.2008.06457.x.
The detection of coherent motion embedded in noise has been widely used as a measure of global visual motion processing. Animal studies have demonstrated that this performance is closely linked to the responses of direction-sensitive neurons in the macaque middle temporal (MT) and medial superior temporal (MST) areas. Despite the strong similarities between the visual cortex of human and that of non-human primates, the human middle temporal complex (area MT+), located in the posterior part of the inferior temporal sulcus and presumably comprising both area MT and area MST, has not consistently been found to share the functional hallmark of MT and MST neurons, i.e. their preference for coherent rather than incoherent visual motion. In order to search for such preferences in human area MT+, blood oxygen level-dependent responses to random dot kinematograms presented in the right visual hemifield were studied here as a function of stimulus size and dot density. The stimulus extensions were varied in such a way as to cover an area either equaling, exceeding or falling below the mean receptive field size of macaque area MT. Unlike the posterior part of human area MT+, the anterior part and its right-hemisphere homolog showed significantly stronger responses to coherent than to incoherent motion. These differences were only present for large stimuli that presumably exceeded the receptive field size of neurons in area MT. Our results suggest that functional magnetic resonance imaging may reveal stronger responses to coherent visual motion in human area MST, provided that the stimulus allows for sufficient summation within the receptive fields. In contrast, functional magnetic resonance imaging may fail to reveal the same dependency for human area MT.
检测噪声中嵌入的连贯运动已被广泛用作衡量全局视觉运动处理能力的指标。动物研究表明，这种表现与猕猴颞中区（MT）和颞上内侧区（MST）中方向敏感神经元的反应密切相关。尽管人类视觉皮层与非人类灵长类动物的视觉皮层有很强的相似性，但位于颞下沟后部、可能包含MT区和MST区的人类颞中复合体（MT+区），并未始终如一地被发现具有MT和MST神经元的功能特征，即它们对连贯而非不连贯视觉运动的偏好。为了在人类MT+区寻找这种偏好，我们在此研究了右视野中呈现的随机点运动图的血氧水平依赖反应，该反应是刺激大小和点密度的函数。刺激范围的变化方式是使其覆盖的面积等于、超过或低于猕猴MT区的平均感受野大小。与人类MT+区后部不同，其前部及其右半球对应区域对连贯运动的反应明显强于对不连贯运动的反应。这些差异仅在可能超过MT区神经元感受野大小的大刺激下才出现。我们的结果表明，如果刺激能在感受野内实现足够的总和，功能磁共振成像可能会揭示人类MST区对连贯视觉运动有更强的反应。相比之下，功能磁共振成像可能无法揭示人类MT区的相同依赖性。
