Mikami A, Newsome W T, Wurtz R H
J Neurophysiol. 1986 Jun;55(6):1328-39. doi: 10.1152/jn.1986.55.6.1328.
We measured the spatial and temporal limits of directional interactions for 105 directionally selective middle temporal (MT) neurons and 26 directionally selective striate (V1) neurons. Directional interactions were measured using sequentially flashed stimuli in which the spatial and temporal intervals between stimuli were systematically varied over a broad range. A direction index was employed to determine the strength of directional interactions for each combination of spatial and temporal intervals tested. The maximum spatial interval for which directional interactions occurred in a particular neuron was positively correlated with receptive-field size and with retinal eccentricity in both MT and V1. The maximum spatial interval was, on average, three times as large in MT as in V1. The maximum temporal interval for which we obtained directional interactions was similar in MT and V1 and did not vary with receptive-field size or eccentricity. The maximum spatial interval for directional interactions as measured with flashed stimuli was positively correlated with the maximum speed of smooth motion that yielded directional responses. MT neurons were directionally selective for higher speeds than were V1 neurons. These observations indicate that the large receptive fields found in MT permit directional interactions over longer distances than do the more limited receptive fields of V1 neurons. A functional advantage is thereby conferred on MT neurons because they detect directional differences for higher speeds than do V1 neurons. Recent psychophysical studies have measured the spatial and temporal limits for the perception of apparent motion in sequentially flashed visual displays. A comparison of the psychophysical results with our physiological data indicates that the spatiotemporal limits for perception are similar to the limits for direction selectivity in MT neurons but differ markedly from those for V1 neurons. These observations suggest a correspondence between neuronal responses in MT and the short-range process of apparent motion.
我们测量了105个方向选择性颞中回（MT）神经元和26个方向选择性纹状皮层（V1）神经元的方向相互作用的空间和时间限度。使用顺序闪烁刺激来测量方向相互作用，其中刺激之间的空间和时间间隔在很宽的范围内系统地变化。采用方向指数来确定所测试的每个空间和时间间隔组合的方向相互作用强度。在特定神经元中发生方向相互作用的最大空间间隔与感受野大小以及MT和V1中的视网膜偏心率呈正相关。平均而言，MT中的最大空间间隔是V1中的三倍。我们获得方向相互作用的最大时间间隔在MT和V1中相似，并且不随感受野大小或偏心率而变化。用闪烁刺激测量的方向相互作用的最大空间间隔与产生方向反应的平滑运动的最大速度呈正相关。MT神经元对速度的方向选择性高于V1神经元。这些观察结果表明，与V1神经元更有限的感受野相比，MT中发现的大感受野允许在更长距离上进行方向相互作用。因此，MT神经元具有功能优势，因为它们比V1神经元能检测更高速度下的方向差异。最近的心理物理学研究测量了顺序闪烁视觉显示中表观运动感知的空间和时间限度。将心理物理学结果与我们的生理数据进行比较表明，感知的时空限度与MT神经元中的方向选择性限度相似，但与V1神经元的限度明显不同。这些观察结果表明MT中的神经元反应与表观运动的短程过程之间存在对应关系。
