Department of Psychology, Boston College, Chestnut Hill, MA, USA.
Neuroimage. 2012 Dec;63(4):1901-8. doi: 10.1016/j.neuroimage.2012.08.043.
A long-standing heuristic in visual neuroscience holds that extrastriate visual cortex is parceled into a dorsal "where" pathway concerned with stimulus position and motion and a ventral "what" pathway concerned with stimulus form. Several recent studies using functional magnetic resonance imaging (fMRI), however, have shown that small changes in the position of a single object can produce reliable changes in activity patterns in object-selective lateral occipital complex (LOC). Although these data demonstrate that information about both object form and position is present at the region level in LOC, the extent to which they reflect joint neuronal tuning to these dimensions is unclear. To measure joint tuning for form and position, we used fMRI to record patterns of activity evoked in LOC and other visual areas while subjects viewed pairs of objects that varied in category content, overall position, and relative object position. Consistent with previous results, multivoxel activity patterns in LOC varied reliably with the category content and position of object pairs. Moreover, activity patterns in the lateral occipital (LO) subregion of LOC varied significantly with the relative positions of objects within pairs, even when absolute pair position was constant. This result provides strong evidence for the existence of neuronal populations in LO which are jointly tuned for both object form (i.e., category) and position.
视觉神经科学中长期存在的一个启发式观点认为，外纹状皮层被分割成一个背侧的“位置”通路，该通路与刺激位置和运动有关，而腹侧的“物体”通路则与刺激形状有关。然而，最近使用功能磁共振成像（fMRI）的几项研究表明，单个物体位置的微小变化可以在物体选择性外侧枕叶复合体（LOC）中产生可靠的活动模式变化。尽管这些数据表明关于物体形状和位置的信息都存在于 LOC 的区域水平，但它们反映出对这些维度的联合神经元调谐的程度尚不清楚。为了测量形状和位置的联合调谐，我们使用 fMRI 记录了在 LOC 和其他视觉区域中观察到的物体对变化时的活动模式，这些物体对在类别内容、整体位置和相对物体位置上有所不同。与先前的结果一致，LOC 中的多体素活动模式与物体对的类别内容和位置可靠地变化。此外，即使绝对物体对位置保持不变，LOC 的外侧枕叶（LO）亚区的活动模式也会随物体对内部的相对位置显著变化。这一结果为 LO 中存在联合调谐物体形状（即类别）和位置的神经元群体提供了有力证据。
