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Prior semantic knowledge facilitates episodic recognition memory for faces. To examine the neural manifestation of the interplay between semantic and episodic memory, we investigated neuroelectric dynamics during the creation (study) and the retrieval (test) of episodic memories for famous and nonfamous faces. Episodic memory effects were evident in several EEG frequency bands: theta (4-8 Hz), alpha (9-13 Hz), and gamma (40-100 Hz). Activity in these bands was differentially modulated by preexisting semantic knowledge and by episodic memory, implicating their different functional roles in memory. More specifically, theta activity and alpha suppression were larger for old compared to new faces at test regardless of fame, but were both larger for famous faces during study. This pattern of selective semantic effects suggests that the theta and alpha responses, which are primarily associated with episodic memory, reflect utilization of semantic information only when it is beneficial for task performance. In contrast, gamma activity decreased between the first (study) and second (test) presentation of a face, but overall was larger for famous than nonfamous faces. Hence, the gamma rhythm seems to be primarily related to activation of preexisting neural representations that may contribute to the formation of new episodic traces. Taken together, these data provide new insights into the complex interaction between semantic and episodic memory for faces and the neural dynamics associated with mnemonic processes.

Holding biological motion (BM), the movements of animate entities, in working memory (WM) is important to our daily social life. However, how BM is maintained in WM remains unknown. The current study investigated this issue and hypothesized that, analogous to BM perception, the human mirror neuron system (MNS) is involved in rehearsing BM in WM. To examine the MNS hypothesis of BM rehearsal, we used an EEG index of mu suppression (8-12 Hz), which has been linked to the MNS. Using a change detection task, we manipulated the BM memory load in three experiments. We predicted that mu suppression in the maintenance phase of WM would be modulated by the BM memory load; moreover, a negative correlation between the number of BM stimuli in WM and the degree of mu suppression may emerge. The results of Experiment 1 were in line with our predictions and revealed that mu suppression increased as the memory load increased from two to four BM stimuli; however, mu suppression then plateaued, as WM could only hold, at most, four BM stimuli. Moreover, the predicted negative correlation was observed. Corroborating the findings of Experiment 1, Experiment 2 further demonstrated that once participants used verbal codes to process the motion information, the mu suppression or modulation by memory load vanished. Finally, Experiment 3 demonstrated that the findings in Experiment 1 were not limited to one specific type of stimuli. Together, these results provide evidence that the MNS underlies the process of rehearsing BM in WM. [ABSTRACT FROM AUTHOR]

We used functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) to measure neural changes associated with training configural processing in congenital prosopagnosia, a condition in which face identification abilities are not properly developed in the absence of brain injury or visual problems. We designed a task that required discriminating faces by their spatial configuration and, after extensive training, prosopagnosic MZ significantly improved at face identification. Event-related potential results revealed that although the N170 was not selective for faces before training, its selectivity after training was normal. fMRI demonstrated increased functional connectivity between ventral occipital temporal face-selective regions (right occipital face area and right fusiform face area) that accompanied improvement in face recognition. Several other regions showed fMRI activity changes with training; the majority of these regions increased connectivity with face-selective regions. Together, the neural mechanisms associated with face recognition improvements involved strengthening early face-selective mechanisms and increased coordination between face-selective and nonselective regions, particularly in the right hemisphere. [ABSTRACT FROM AUTHOR]