Grady C L, Furey M L, Pietrini P, Horwitz B, Rapoport S I
Rotman Research Institute, Baycrest Centre for Geriatric Care, University of Toronto, Toronto, Ontario, Canada.
Brain. 2001 Apr;124(Pt 4):739-56. doi: 10.1093/brain/124.4.739.
To examine functional interactions between prefrontal and medial temporal brain areas during face memory, blood flow was measured in patients with Alzheimer's disease and healthy controls using PET. We hypothesized that controls would show correlated activity between frontal and posterior brain areas, including the medial temporal cortex, whereas patients would not, although frontal activity per se might be spared or even increased compared with controls. We used a delayed match to sample paradigm with delays from 1 to 16 s. There was no change in recognition accuracy with increasing delay in controls, whereas patients showed impaired recognition over all delays that worsened as delay increased. Controls showed increased activity in the bilateral prefrontal and parietal cortex with increasing delay, whereas the patients had increased activity in the right prefrontal, anterior cingulate and left amygdala. Increased activity in the right prefrontal cortex was associated with better memory performance in both groups and activity in the left amygdala was correlated with better performance in the patients. Based on these task and behavioural effects, we examined functional connectivity of the right prefrontal cortex and left amygdala in both groups by determining those areas whose activity was correlated with activity in these regions. In controls, activity in the right prefrontal cortex was positively correlated with blood flow in the left prefrontal cortex, bilateral extrastriate and parietal areas and the right hippocampus. In patients, activity in the right prefrontal cortex was correlated mainly with other prefrontal regions. Areas where activity was correlated with the left amygdala in patients included the bilateral posterior parahippocampal gyri, a number of left prefrontal regions, anterior and posterior cingulate, thalamus, and insula. Controls had a relatively restricted set of regions where activity correlated with the left amygdala, mainly temporal and occipital areas. These results support the idea of a functional disconnection between the prefrontal cortex and the hippocampus in Alzheimer's disease and suggest that memory breakdown in early Alzheimer's disease is related to a reduction in the integrated activity within a distributed network that includes these two areas. The unexpected finding of increased involvement of the amygdala suggests that the patients may have processed the emotional content of the faces to a greater degree than did the controls. Furthermore, the positive association between amygdala activity and memory performance in the patients suggests a possible compensatory role for an emotion-related network of regions.
为了研究面部记忆过程中前额叶与内侧颞叶脑区之间的功能相互作用，我们使用正电子发射断层扫描（PET）测量了阿尔茨海默病患者和健康对照者的脑血流。我们假设，与对照组相比，健康对照者的额叶和后脑区（包括内侧颞叶皮质）之间会表现出相关活动，而阿尔茨海默病患者则不会，尽管患者额叶活动本身可能得以保留甚至增强。我们采用延迟匹配样本范式，延迟时间从1秒到16秒不等。对照组中，随着延迟时间增加，识别准确率没有变化，而阿尔茨海默病患者在所有延迟时间下的识别能力均受损，且随着延迟时间增加，这种损害会加剧。对照组中，随着延迟时间增加，双侧前额叶和顶叶皮质的活动增强，而阿尔茨海默病患者右侧前额叶、前扣带回和左侧杏仁核的活动增强。两组中，右侧前额叶皮质活动增强均与更好的记忆表现相关，而在阿尔茨海默病患者中，左侧杏仁核的活动与更好的表现相关。基于这些任务和行为效应，我们通过确定那些活动与这些区域的活动相关的脑区，来研究两组中右侧前额叶皮质和左侧杏仁核的功能连接。在对照组中，右侧前额叶皮质的活动与左侧前额叶皮质、双侧纹外区和顶叶区域以及右侧海马体的血流呈正相关。在阿尔茨海默病患者中，右侧前额叶皮质的活动主要与其他前额叶区域相关。在阿尔茨海默病患者中，与左侧杏仁核活动相关的脑区包括双侧海马旁回后部、多个左侧前额叶区域、前扣带回和后扣带回、丘脑和脑岛。对照组中，与左侧杏仁核活动相关的脑区相对有限，主要是颞叶和枕叶区域。这些结果支持了阿尔茨海默病患者前额叶皮质与海马体之间存在功能脱节的观点，并表明早期阿尔茨海默病的记忆衰退与包括这两个区域在内的分布式网络内整合活动的减少有关。杏仁核参与度增加这一意外发现表明，患者对面部情感内容的处理程度可能高于对照组。此外，患者杏仁核活动与记忆表现之间的正相关表明，与情感相关的脑区网络可能具有代偿作用。
