McIntosh Anthony Randal, Rajah M Natasha, Lobaugh Nancy J
Rotman Research Institute of Baycrest Centre, University of Toronto, Toronto, Ontario M6A 2E1, Canada.
J Neurosci. 2003 Jul 23;23(16):6520-8. doi: 10.1523/JNEUROSCI.23-16-06520.2003.
Learning with awareness is believed to require the involvement of the medial temporal lobe (MTL). In this study, the hypothesis tested was that this involvement is best appreciated by the pattern of MTL functional connectivity with other brain areas. In a sensory learning paradigm, human subjects were classified as AWARE or UNAWARE, on the basis of whether they noted that one of two tones predicted a visual event. Only AWARE subjects acquired and reversed a differential response to the tones. However, learned facilitation was evident in both groups. MTL activity, indexed by blood flow changes measured with positron emission tomography, was correlated with facilitation in both groups but in opposite directions (greater MTL activity was related to less facilitation in AWARE subjects but more facilitation in UNAWARE subjects). Discrimination and reversal in AWARE subjects involved anterior medial, inferior prefrontal, and lateral occipital cortices. Furthermore, unique regional patterns of MTL functional connectivity were observed: AWARE subjects engaged dorsolateral prefrontal and lateral occipital cortices, whereas UNAWARE subjects showed a more spatially restricted network involving contralateral MTL regions and the thalamus. In the AWARE group, the MTL functional connectivity pattern overlapped with regions associated with facilitation and discrimination, but in UNAWARE subjects, the MTL pattern was related only to facilitation. These results suggest that the MTL and functional connected regions, including dorsolateral and medial prefrontal cortex, acted to link facilitation and discrimination patterns in AWARE subjects. Thus, the contribution of the MTL to learning and awareness is shaped by the pattern of interregional interactions, the neural context.
有意识学习被认为需要内侧颞叶（MTL）的参与。在本研究中，所检验的假设是，通过MTL与其他脑区的功能连接模式能最好地理解这种参与。在一种感觉学习范式中，根据人类受试者是否注意到两个音调之一预测了一个视觉事件，将他们分为有意识组（AWARE）或无意识组（UNAWARE）。只有有意识组的受试者获得并逆转了对音调的差异反应。然而，两组都出现了学习促进现象。通过正电子发射断层扫描测量的血流变化所索引的MTL活动，在两组中均与促进作用相关，但方向相反（有意识组受试者中，MTL活动越强，促进作用越小；无意识组受试者中，MTL活动越强，促进作用越大）。有意识组受试者的辨别和逆转涉及前内侧、额下和枕外侧皮质。此外，还观察到MTL功能连接的独特区域模式：有意识组受试者激活了背外侧前额叶和枕外侧皮质，而无意识组受试者表现出一个空间上更受限的网络，涉及对侧MTL区域和丘脑。在有意识组中，MTL功能连接模式与与促进和辨别相关的区域重叠，但在无意识组受试者中，MTL模式仅与促进作用相关。这些结果表明，MTL和功能连接区域，包括背外侧和内侧前额叶皮质，在有意识组受试者中起到了连接促进和辨别模式的作用。因此，MTL对学习和意识的贡献是由区域间相互作用的模式，即神经背景所塑造的。
