Neuronal basis of contrast discrimination
Neuronal basis of contrast discrimination
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DOI：
10.1016/s0042-6989(98)00113-8
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发表时间：
1999-01-01
期刊：
影响因子：
1.8
通讯作者：
Heeger, DJ
中科院分区：
文献类型：
--
作者：
Boynton, GM;Demb, JB;Heeger, DJ
将心理物理对比增量阈值与从功能性磁共振成像（fMRI）推断出的神经元反应进行了比较，以检验对比辨别判断受早期视觉皮层区域的神经元信号限制这一假设。fMRI被用于测量几个人类可识别的视觉皮层区域中每个区域作为刺激对比函数的大脑活动。使用时间2AFC范式，在一系列基线对比下测量相同刺激的对比增量阈值。通过假设以下几点对fMRI反应和心理物理测量进行了比较：（1）fMRI反应与局部平均神经元活动成正比；（2）受试者选择能引起更大平均神经元活动的刺激间隔；（3）观察者心理物理判断的变异性是由加性（独立同分布）噪声引起的。基于这些假设，发现视觉区域V1、V2d、V3d和V3A中的fMRI反应与心理物理判断一致，即当这些大脑区域中的每个区域的fMRI反应增加一个标准量时，就能检测到对比增量。因此，大量神经元的集合活动能够相当好地预测行为表现。数据还表明，早期视觉皮层的对比增益系统地取决于空间频率。（C）1998年爱思唯尔科学有限公司。保留所有权利。
Psychophysical contrast increment thresholds were compared with neuronal responses, inferred from functional magnetic resonance imaging (fMRI) to test the hypothesis that contrast discrimination judgements are limited by neuronal signals in early visual cortical areas. FMRI was used to measure human brain activity as a function of stimulus contrast, in each of several identifiable visual cortical areas. Contrast increment thresholds were measured for the same stimuli across a range of baseline contrasts using a temporal 2AFC paradigm. FMRI responses and psychophysical measurements were compared by assuming that: (1) fMRI responses are proportional to local average neuronal activity; (2) subjects choose the stimulus interval that evoked the greater average neuronal activity; and (3) variability in the observer's psychophysical judgements was due to additive (IID) noise. With these assumptions, FMRI responses in visual areas VI, V2d, V3d and V3A were found to be consistent with the psychophysical judgements, i.e. a contrast increment was detected when the fMRI responses in each of these brain areas increased by a criterion amount. Thus, the pooled activity of large numbers of neurons can reasonably well predict behavioral performance. The data also suggest that contrast gain in early visual cortex depends systematically on spatial frequency. (C) 1998 Elsevier Science Ltd. All rights reserved.