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
The dorsolateral prefrontal cortex(DLPFC) is considered to play a crucial role in many high-level functions, such as cognitive control and emotional regulation. Many studies have reported that the DLPFC can be activated during the processing of emotional information in tasks requiring working memory. However, it is still not clear whether modulating the activity of the DLPFC influences emotional perception in a detection task. In the present study, using transcranial direct-current stimulation(tDCS), we investigated(1) whether modulating the right DLPFC influences emotional face processing in a detection task, and(2) whether the DLPFC plays equal roles in processing positive and negative emotional faces. The results showed that anodal tDCS over the right DLPFC specifically facilitated the perception of positive faces, but did not influence the processing of negative faces. In addition, anodal tDCS over the right primary visual cortex enhanced performance in the detection task regardless of emotional valence. Our findings suggest, for the first time,that modulating the right DLPFC influences emotional face perception, especially faces showing positive emotion.
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
