Stereoscopic processing of absolute and relative disparity in human visual cortex
Stereoscopic processing of absolute and relative disparity in human visual cortex
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DOI：
10.1152/jn.01042.2003
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发表时间：
2004-09-01
影响因子：
2.5
通讯作者：
Heeger, DJ
中科院分区：
文献类型：
--
作者：
Neri, P;Bridge, H;Heeger, DJ
立体视觉主要依赖于物体之间的相对深度差异，而不是它们与眼睛注视的地方的绝对深度距离。然而，相对差异是从绝对差异计算出来的，目前还不知道这两个阶段在人脑中的哪个位置。使用功能磁共振成像（fMRI），我们评估了绝对和相对视差选择性与立体刺激组成的对透明平面的深度，其中的绝对和相对视差信号可以独立操纵（在一个局部空间尺度）。在实验1中，相对视差保持恒定，而绝对视差在一半的试验块（“混合”块）中变化，并在剩余的一半（“相同”块）中保持恒定，在块之间交替。由于神经元的反应进行适应，并减少其放电率重复呈现的有效刺激，功能性磁共振成像信号反映活动的单位选择性的绝对差距预计将是较小的“相同”块相比，“混合”的。实验2同样操纵相对差异而不是绝对差异。两项实验的结果均与适应一致，不同视觉区域的影响不同，例如1）背侧区（V3 A、MT+/V5、V7）对绝对差异的适应性大于对相对差异的适应性; 2）腹侧区（hV 4、V8/V4 alpha）对两者的适应性相同; 3）早期视觉区域（V1、V2、V3）在两项实验中均表现出较小的影响。这些结果表明，在背侧区的处理可能主要依赖于绝对差距的信息，而腹侧区之间的两种类型的立体信息分裂的神经资源，以保持一个重要的代表性的相对差距。
Stereoscopic vision relies mainly on relative depth differences between objects rather than on their absolute distance in depth from where the eyes fixate. However, relative disparities are computed from absolute disparities, and it is not known where these two stages are represented in the human brain. Using functional MRI ( fMRI), we assessed absolute and relative disparity selectivity with stereoscopic stimuli consisting of pairs of transparent planes in depth in which the absolute and relative disparity signals could be independently manipulated ( at a local spatial scale). In experiment 1, relative disparity was kept constant, while absolute disparity was varied in one-half the blocks of trials ("mixed" blocks) and kept constant in the remaining one-half ("same" blocks), alternating between blocks. Because neuronal responses undergo adaptation and reduce their firing rate following repeated presentation of an effective stimulus, the fMRI signal reflecting activity of units selective for absolute disparity is expected to be smaller during "same" blocks as compared with "mixed" ones. Experiment 2 similarly manipulated relative disparity rather than absolute disparity. The results from both experiments were consistent with adaptation with differential effects across visual areas such that 1) dorsal areas (V3A, MT+/V5, V7) showed more adaptation to absolute than to relative disparity; 2) ventral areas (hV4, V8/V4alpha) showed an equal adaptation to both; and 3) early visual areas (V1, V2, V3) showed a small effect in both experiments. These results indicate that processing in dorsal areas may rely mostly on information about absolute disparities, while ventral areas split neural resources between the two types of stereoscopic information so as to maintain an important representation of relative disparity.