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猕猴丘脑和皮层中注意力注视的影响。

Effect of attentive fixation in macaque thalamus and cortex.

作者信息

Bender D B, Youakim M

机构信息

Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York 14214, USA.

出版信息

J Neurophysiol. 2001 Jan;85(1):219-34. doi: 10.1152/jn.2001.85.1.219.

Abstract

Attentional modulation of neuronal responsiveness is common in many areas of visual cortex. We examined whether attentional modulation in the visual thalamus was quantitatively similar to that in cortex. Identical procedures and apparatus were used to compare attentional modulation of single neurons in seven different areas of the visual system: the lateral geniculate, three visual subdivisions of the pulvinar [inferior, lateral, dorsomedial part of lateral pulvinar (Pdm)], and three areas of extrastriate cortex representing early, intermediate, and late stages of cortical processing (V2, V4/PM, area 7a). A simple fixation task controlled transitions among three attentive states. The animal waited for a fixation point to appear (ready state), fixated the point until it dimmed (fixation state), and then waited idly to begin the next trial (idle state). Attentional modulation was estimated by flashing an identical, irrelevant stimulus in a neuron's receptive field during each of the three states; the three responses defined a "response vector" whose deviation from the line of equal response in all three states (the main diagonal) indicated the character and magnitude of attentional modulation. Attentional modulation was present in all visual areas except the lateral geniculate, indicating that modulation was of central origin. Prevalence of modulation was modest (26%) in pulvinar, and increased from 21% in V2 to 43% in 7a. Modulation had a push-pull character (as many cells facilitated as suppressed) with respect to the fixation state in all areas except Pdm where all cells were suppressed during fixation. The absolute magnitude of attentional modulation, measured by the angle between response vector and main diagonal expressed as a percent of the maximum possible angle, differed among brain areas. Magnitude of modulation was modest in the pulvinar (19-26%), and increased from 22% in V2 to 41% in 7a. However, average trial-to-trial variability of response, measured by the coefficient of variation, also increased across brain areas so that its difference among areas accounted for more than 90% of the difference in modulation magnitude among areas. We also measured attentional modulation by the ratio of cell discharge due to attention divided by discharge variability. The resulting signal-to-noise ratio of attention was small and constant, 1.3 +/- 10%, across all areas of pulvinar and cortex. We conclude that the pulvinar, but not the lateral geniculate, is as strongly affected by attentional state as any area of visual cortex we studied and that attentional modulation amplitude is closely tied to intrinsic variability of response.

摘要

神经元反应性的注意力调制在视觉皮层的许多区域都很常见。我们研究了视觉丘脑的注意力调制在数量上是否与皮层中的相似。使用相同的程序和仪器来比较视觉系统七个不同区域中单个神经元的注意力调制:外侧膝状体、丘脑枕的三个视觉亚区[外侧丘脑枕的下部、外侧、背内侧部分(Pdm)],以及代表皮层处理早期、中期和晚期阶段的三个纹外皮层区域(V2、V4/PM、7a区)。一个简单的注视任务控制三种注意力状态之间的转换。动物等待注视点出现(准备状态),注视该点直到其变暗(注视状态),然后空闲等待开始下一次试验(空闲状态)。通过在三种状态的每一种状态下,在神经元的感受野中闪现相同的、不相关的刺激来估计注意力调制;这三种反应定义了一个“反应向量”,其在所有三种状态下与等反应线(主对角线)的偏差表明了注意力调制的特征和幅度。除外侧膝状体外,所有视觉区域都存在注意力调制,这表明调制起源于中枢。在丘脑枕中调制的发生率适中(26%),并且从V2中的21%增加到7a中的43%。除Pdm外,在所有区域中,相对于注视状态,调制具有推挽特性(促进的细胞与抑制的细胞一样多),在Pdm中,所有细胞在注视期间都被抑制。通过反应向量与主对角线之间的夹角(表示为最大可能角度的百分比)测量的注意力调制的绝对幅度在不同脑区有所不同。在丘脑枕中调制幅度适中(19 - 26%),并且从V2中的22%增加到7a中的41%。然而,通过变异系数测量的反应的平均逐次试验变异性也在不同脑区增加,因此其在不同区域之间的差异占不同区域调制幅度差异的90%以上。我们还通过注意力引起的细胞放电除以放电变异性的比率来测量注意力调制。在丘脑枕和皮层的所有区域中,由此产生的注意力信噪比很小且恒定,为1.3±10%。我们得出结论,丘脑枕而非外侧膝状体,与我们研究的任何视觉皮层区域一样,受到注意力状态的强烈影响,并且注意力调制幅度与反应的内在变异性密切相关。

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