A previous functional magnetic resonance imaging study reported evidence for parallel memory traces in the hippocampus： a controlled match signal detecting matches to internally-generated goal states and an automatic mismatch signal identifying unpredicted perceptual novelty. However, the timing information in this process is unknown. In the current study, facilitated by the high spatial and temporal resolution of intracranial recording from human patients, we confirmed that the left posterior hippocampus played an important role in the goal match enhancement effect, in which combinations of object identity and location were involved. We also found that this effect happened within 520 ms to 735 ms after the probe onset, ＊150 ms later than the perceptual mismatch enhancement found bilaterally in both the anterior and posterior hippocampus. More specifically, the latency of the perceptual mismatch enhancement effect of the right hippocampus was positively correlated with the performance accuracy. These results suggested that the hippocampus is crucial in working memory if features binding with location are involved in the task and the goal match enhancement effect happens after perceptual mismatch enhancement, implying the dissociation of different components of working memory at the hippocampus. Moreover, single trial decoding results suggested that theintracranial field potential response in the right hippocampus can classify the match or switch task. This is consistent with the findings that the right hippocampal activity observed during the simulation of the future events may reflect the encoding of the simulation into memory.
Bing NiRuijie WuTao YuHongwei ZhuYongjie LiZuxiang Liu
Stress from dominance ranks in human societies, or that of other social animals, especially nonhuman primates, can have negative influences on health. Individuals holding different social status may be burdened with various stress levels. The middle class experiences a special stress situation within the dominance hierarchy due to its position between the higher and lower classes. Behaviorally, questions about where middle-class stress comes from and how individuals adapt to middle-class stress remain poorly understood in nonhuman primates. In the present study, social interactions, including aggression, avoidance, grooming and mounting behaviors, between beta males, as well as among group members holding higher or lower social status, were analyzed in captive male-only cynomolgus monkey groups. We found that aggressive tension from the higher hierarchy members was the main origin of stress for middle- class individuals. However, behaviors such as attacking lower hierarchy members immediately after being the recipient of aggression, as well as increased avoidance, grooming and mounting toward both higher and lower hierarchy members helped alleviate middle-class stress and were particular adaptations to middle-class social status.
Functional magnetic resonance imaging（fMRI）is one of the most commonly used methods in cognitive neuroscience on humans.In recent decades,fMRI has also been used in the awake monkey experiments to localize functional brain areas and to compare the functional differences between human and monkey brains.Several procedures and paradigms have been developed to maintain proper head fixation and to perform motion control training.In this study,we extended the application of fMRI to awake cats without training,receiving a flickering checkerboard visual stimulus projected to a screen in front of them in a block-design paradigm.We found that body movement-induced non-rigid motion introduced artifacts into the functional scans,especially those around the eye and neck.To correct for these artifacts,we developed two methods：one for general experimental design,and the other for studies of whether a checkerboard task could be used as a localizer to optimize the motioncorrection parameters.The results demonstrated that,with proper animal fixation and motion correction procedures,it is possible to perform fMRI experiments with untrained awake cats.
Manxiu MaChencan QianYanxia LiZhentao ZuoZuxiang Liu
