Hietanen J K, Perrett D I, Oram M W, Benson P J, Dittrich W H
Department of Psychology, University of St. Andrews, Fife, UK.
Exp Brain Res. 1992;89(1):157-71. doi: 10.1007/BF00229013.
Neural mechanisms underlying recognition of objects must overcome the changes in an object's appearance caused by inconsistent viewing conditions, particularly those that occur with changes in lighting. In humans, lesions to the posterior visual association cortex can impair the ability to recognize objects and faces across different lighting conditions. Inferotemporal lesions in monkey have been shown to produce a similar difficulty in object matching tasks. Here we report on the extent to which cell responses selective for the face and other views of the head in monkey temporal cortex tolerate changes in lighting. For each cell studied the (preferred) head view eliciting maximal response was first established under normal lighting. Cells were then tested with the preferred head view lit from different directions (i.e. front, above, below or from the side). Responses of some cells failed to show complete generalization across all lighting conditions but together as a "population" they responded equally strongly under all four lighting conditions. Further tests on sub-groups of cells revealed that stimulus selectivity was maintained despite unusual lighting. The cells discriminated between head and control stimuli and between different views of the head independent of the lighting direction. The results indicate that constancy of recognition across different lighting conditions is apparent in the responses of single cells in the temporal cortex. Lighting constancy appears to be established by matching the retinal image to view-specific descriptions of objects (i.e. neurons which compute object structure from a limited range of perspective views).
物体识别背后的神经机制必须克服由不一致的观察条件所引起的物体外观变化，尤其是那些随着光照变化而出现的变化。在人类中，视觉后联合皮层受损会损害在不同光照条件下识别物体和面孔的能力。猴子的颞下叶损伤已被证明在物体匹配任务中会产生类似的困难。在这里，我们报告了猴子颞叶皮层中对面部和头部其他视图具有选择性的细胞反应在多大程度上能够耐受光照变化。对于所研究的每个细胞，首先在正常光照下确定引发最大反应的（偏好的）头部视图。然后用从不同方向（即正面、上方、下方或侧面）照亮的偏好头部视图对细胞进行测试。一些细胞的反应未能在所有光照条件下都表现出完全的泛化，但作为一个“群体”，它们在所有四种光照条件下的反应同样强烈。对细胞亚组的进一步测试表明，尽管光照异常，刺激选择性仍然保持。这些细胞能够区分头部和对照刺激，以及头部的不同视图，而与光照方向无关。结果表明，在颞叶皮层单个细胞的反应中，不同光照条件下的识别恒常性是明显的。光照恒常性似乎是通过将视网膜图像与物体的视图特定描述相匹配来建立的（即从有限的视角计算物体结构的神经元）。
