Badgaiyan Rajendra D
Assistant Professor, Harvard Medical School, and Associate Neuroscientist, Massachusetts General Hospital, Boston, MA 02114.
Elements (Que). 2005;3(3):8-12.
The study of consciousness has been limited primarily to philosophical domain. There are a number of conceptual and methodological issues that have prevented scientific investigation of conscious experience. We began the investigation by exploring its cognitive components. Since awareness is an important component, we used neuroimaging techniques to study the brain processing of awareness using memory as a model. It is known that in the tests of 'nonconscious memory' subjects retrieve studied items without becoming consciously aware of retrieval. In contrast, they are fully aware in conscious memory tests. Spatial and temporal patterns of cortical activities observed during the two forms of memory were analyzed to understand neural network that might be associated with the awareness of retrieval. It appears that during conscious recollection, studied items are first retrieved nonconsciously. Thereafter, a reentrant signaling loop is activated between the extrastriate area and frontal cortex. Experiments suggest that this loop may be responsible for the awareness of nonconsciously retrieved information. Further characterization of the extrastriate-frontal connectivity may help explain the neural mechanism of conscious experience.
意识的研究主要局限于哲学领域。存在一些概念和方法上的问题阻碍了对意识体验的科学研究。我们通过探索其认知成分来展开研究。由于觉知是一个重要成分，我们使用神经成像技术，以记忆为模型来研究大脑对觉知的处理过程。众所周知，在“非意识记忆”测试中，受试者能提取已学项目但并未有意识地察觉到提取过程。相比之下，在意识记忆测试中他们则完全有意识。分析这两种记忆形式中观察到的皮质活动的空间和时间模式，以了解可能与提取觉知相关的神经网络。似乎在有意识回忆期间，已学项目首先是被无意识地提取。此后，一个折返信号回路在纹外区和额叶皮质之间被激活。实验表明，这个回路可能负责对无意识提取信息的觉知。对纹外区 - 额叶连接性的进一步表征可能有助于解释意识体验的神经机制。
