Baseline to task increases in theta EEG were observed at

Baseline-to-task increases in theta EEG were observed at frontal, temporal and parietal electrode sites during fact and source recall. These findings are consistent with the adult SM neuroimaging literature (see Spaniol et al., 2009 for a review). To elaborate, hippocampal encoding activation is greater for correctly identified source items compared with incorrectly identified source items (Davachi, 2006; Mayes et al., 2007). Adult fMRI studies have found that, in contrast to old/new item recognition, source retrieval is associated with greater activation in the left prefrontal cortex (Dobbins et al., 2002; Mitchell et al., 2004; Nolde et al., 1998; Ranganath et al., 2000; Rugg et al., 1999). In addition, the anterior, dorsolateral, and ventrolateral regions of the prefrontal cortex may differentially support source memory (Mitchell and Johnson, 2009). As proposed by Blumenfeld and Ranganath (2007), the ventrolateral prefrontal cortex may be involved in the control processes that select the goal-relevant features of items, whereas dorsolateral prefrontal cortex activation supports elaboration and organization of multiple features (Staresina and Davachi, 2006). Parietal cortex activity has also been linked to encoding and retrieval of source information. Specifically, the parietal cortex is involved in the perceptual binding of feature information (Uncapher et al., 2006) and in directing attention toward relevant source features (Vilberg and Rugg, 2007). These results suggest that the frontal, temporal, and parietal lobe Dorsomorphin regions involved in episodic remembering in adults are also activated during episodic recall in middle childhood. Although this present investigation focused on patterns of brain electrical activity during retrieval, it would also be worthwhile for future investigations to examine whether increases in theta band power would be observed during encoding of source items subsequently recalled correctly. Additional research is needed to understand the extent to which prefrontal, temporal, and parietal lobe regions interact during encoding and retrieval of item and SM judgments. To elaborate, it would be worthwhile to examine measures of functional connectivity using EEG coherence, defined as the frequency-dependent squared cross correlation between two electrode sites (Nunez, 1981; Thatcher et al., 1987). In adults, evidence suggests that the prefrontal cortex regulates top-down processing of posterior brain activity, and that this regulation supports later SM (Summerfield et al., 2006). Task-related functional connectivity of temporo-parietal memory networks also supports retrieval processes (Hirose et al., 2013). Very little is known about the developmental trends in functional brain connectivity that support early memory formation. Menon et al. (2005) found that the neural organization of memory encoding changes from childhood to adolescence. Specifically, the authors found age-related decreases in medial temporal lobe activation and age-related increases in functional connectivity between medial temporal lobe and prefrontal cortex regions (Menon et al., 2005). Future research should examine whether task-related changes in frontal-parietal and frontal-temporal EEG coherence are evident during SM processing, as previous investigations have documented these changes in early childhood during working memory (Bell and Wolfe, 2007).
Conflict of interest
Acknowledgements The research reported here represents a portion the first author\'s dissertation research. She would like to thank her dissertation committee members (Kirby Deater-Deckard, Kurt Hoffman, and Kee Jeong Kim) for their input on this project. We are grateful to the families for their participation. We wish to thank Anjolii Diaz, Candace Hummer and Andrea Ton for assistance with data collection and coding. Data collection and analysis was supported by grant HD049878 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). Partial support for the preparation of this manuscript was provided by grant R305B130012 from the Institute of Education Sciences (IES). The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of IES, NICHD or the National Institutes of Health.