Wolfson Centre for Clinical and Cognitive Neuroscience, School of Psychology, Bangor University, Bangor, United Kingdom.
J Neurophysiol. 2012 Jan;107(2):628-39. doi: 10.1152/jn.00105.2011. Epub 2011 Oct 19.
How is working memory for different visual categories supported in the brain? Do the same principles of cortical specialization that govern the initial processing and encoding of visual stimuli also apply to their short-term maintenance? We investigated these questions with a delayed discrimination paradigm for faces, bodies, flowers, and scenes and applied both univariate and multivariate analyses to functional magnetic resonance imaging (fMRI) data. Activity during encoding followed the well-known specialization in posterior areas. During the delay interval, activity shifted to frontal and parietal regions but was not specialized for category. Conversely, activity in visual areas returned to baseline during that interval but showed some evidence of category specialization on multivariate pattern analysis (MVPA). We conclude that principles of cortical activation differ between encoding and maintenance of visual material. Whereas perceptual processes rely on specialized regions in occipitotemporal cortex, maintenance involves the activation of a frontoparietal network that seems to require little specialization at the category level. We also confirm previous findings that MVPA can extract information from fMRI signals in the absence of suprathreshold activation and that such signals from visual areas can reflect the material stored in memory.
大脑如何支持不同视觉类别的工作记忆?控制视觉刺激初始处理和编码的皮质专业化相同原则是否也适用于它们的短期维持?我们使用面孔、身体、花朵和场景的延迟辨别范式研究了这些问题,并对功能磁共振成像 (fMRI) 数据应用了单变量和多变量分析。在编码过程中的活动遵循了众所周知的后区专业化。在延迟间隔期间,活动转移到额顶叶区域,但没有针对类别进行专业化。相反,在那段时间内,视觉区域的活动恢复到基线,但在多变量模式分析 (MVPA) 上显示出一些类别专业化的证据。我们的结论是,编码和维持视觉材料之间的皮质激活原则不同。虽然感知过程依赖于枕颞皮质中的专门区域,但维持涉及到额顶叶网络的激活,该网络似乎在类别水平上不需要专门化。我们还证实了之前的发现,即 MVPA 可以从 fMRI 信号中提取信息,而无需超阈值激活,并且来自视觉区域的这种信号可以反映存储在记忆中的材料。