Noguchi Yasuki, Inui Koji, Kakigi Ryusuke
Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan.
J Neurosci. 2004 Jul 14;24(28):6283-90. doi: 10.1523/JNEUROSCI.0655-04.2004.
When the same visual stimulus is repeatedly presented with a brief interval, the brain responses to that stimulus are attenuated relative to those at first presentation [neural adaptation (NA)]. Although this effect has been widely observed in various regions of human brain, its temporal dynamics as a neuronal population has been mostly unclear. In the present study, we used a magnetoencephalography (MEG) and conducted a macrolevel investigation of the temporal profiles of the NA occurring in the human visual ventral stream. The combination of MEG with our previous random dot blinking method isolated the neural responses in the higher visual cortex relating to shape perception. We dissociated three dimensions of the NA: activation strength, peak latency, and temporal duration of neural response. The results revealed that visual responses to the repeated compared with novel stimulus showed a significant reduction in both activation strength and peak latency but not in the duration of neural processing. Furthermore, this acceleration of peak latency showed a significant correlation with reaction time of the subjects, whereas no correlation was found between the reaction time and the temporal duration of neural responses. These results indicate that (1) the NA involves the brain response changes in the temporal domain as well as the response attenuation reported previously, and (2) this temporal change is primarily observed as a rapid rising of "what" responses, rather than a temporal shortening of neural response curves within the visual ventral stream as considered previously.
当相同的视觉刺激以短暂的间隔重复呈现时,相对于首次呈现时,大脑对该刺激的反应会减弱[神经适应性(NA)]。尽管这种效应已在人类大脑的各个区域广泛观察到,但其作为神经元群体的时间动态大多仍不清楚。在本研究中,我们使用了脑磁图(MEG),并对人类视觉腹侧流中发生的NA的时间特征进行了宏观层面的研究。MEG与我们之前的随机点闪烁方法相结合,分离出了与形状感知相关的高级视觉皮层中的神经反应。我们区分了NA的三个维度:激活强度、峰值潜伏期和神经反应的持续时间。结果显示,与新刺激相比,对重复刺激的视觉反应在激活强度和峰值潜伏期上均显著降低,但神经处理的持续时间没有变化。此外,峰值潜伏期的这种加速与受试者的反应时间显著相关,而反应时间与神经反应的持续时间之间没有相关性。这些结果表明:(1)NA不仅涉及先前报道的反应衰减,还涉及大脑反应在时间域的变化;(2)这种时间变化主要表现为“什么”反应的快速上升,而不是如先前认为的那样是视觉腹侧流内神经反应曲线的时间缩短。