Neural Changes Underlying the Development of Episodic Memory During Middle Childhood
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G Model DCN-113; No. of Pages 15 ARTICLE IN PRESS Developmental Cognitive Neuroscience xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Developmental Cognitive Neuroscience j ournal homepage: http://www.elsevier.com/locate/dcn Review Neural changes underlying the development of episodic memory during middle childhood a,∗ b,∗∗ Simona Ghetti , Silvia A. Bunge a Department of Psychology & Center for Mind and Brain, University of California at Davis, United States b Department of Psychology & Helen Wills Neuroscience Institute, University of California at Berkeley, United States a r t i c l e i n f o a b s t r a c t Article history: Episodic memory is central to the human experience. In typically developing children, Received 28 November 2011 episodic memory improves rapidly during middle childhood. While the developmental Received in revised form 26 May 2012 cognitive neuroscience of episodic memory remains largely uncharted, recent research Accepted 28 May 2012 has begun to provide important insights. It has long been assumed that hippocampus- dependent binding mechanisms are in place by early childhood, and that improvements Keywords: in episodic memory observed during middle childhood result from the protracted devel- Memory Development opment of the prefrontal cortex. We revisit the notion that binding mechanisms are Hippocampus age-invariant, and propose that changes in the hippocampus and its projections to cor- Prefrontal cortex tical regions also contribute to the development of episodic memory. We further review Parietal cortex the role of developmental changes in lateral prefrontal and parietal cortices in this develop- White matter ment. Finally, we discuss changes in white matter tracts connecting brain regions that are critical for episodic memory. Overall, we argue that changes in episodic memory emerge from the concerted effort of a network of relevant brain structures. © 2012 Elsevier Ltd. All rights reserved. Contents 1. Episodic memory is a fundamental component of human cognition . 00 2. Protracted behavioral development of episodic memory during middle childhood . 00 3. The neural basis of the development of episodic memory. 00 3.1. Changes in medial-temporal lobes and the development of episodic representation . 00 3.2. Changes in prefrontal cortex and the development of controlled encoding and retrieval processes . 00 3.3. Structural and functional changes in fronto-temporal networks . 00 3.4. Exploring the role of the parietal lobes in episodic memory development . 00 4. Episodic memory beyond middle childhood . 00 5. Brain development in context: factors that may influence the development of episodic memory . 00 6. Implications for education. 00 7. Conclusions . 00 Conflict of interest . 00 Acknowledgments . 00 References . 00 Abbreviations: DLPFC, dorsolateral PFC; fMRI, functional magnetic resonance imaging; lPFC, lateral PFC; MTL, medial temporal lobes; PHG, parahippocampal gyrus; PFC, prefrontal cortex; PPC, posterior parietal cortex; DTI, diffusion tensor imaging. ∗ Corresponding author. Tel.: +1 530 747 3803; fax: +1 530 297 4400. ∗∗ Corresponding author. Tel.: +1 510 642 7141; fax: +1 510 642 5293. E-mail addresses: [email protected] (S. Ghetti), [email protected] (S.A. Bunge). 1878-9293/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dcn.2012.05.002 Please cite this article in press as: Ghetti, S., Bunge, S.A., Neural changes underlying the development of episodic memory during middle childhood. Dev. Cogn. Neurosci. (2012), http://dx.doi.org/10.1016/j.dcn.2012.05.002 G Model DCN-113; No. of Pages 15 ARTICLE IN PRESS 2 S. Ghetti, S.A. Bunge / Developmental Cognitive Neuroscience xxx (2012) xxx–xxx 1. Episodic memory is a fundamental component of 2. Protracted behavioral development of episodic human cognition memory during middle childhood Episodic memory is the capacity to form and retrieve Infants and young children exhibit impressive abilities conscious memories of specific past events (Tulving, to remember past events (Bauer, 2007; Howe et al., 2009) 1972). Specifically, episodic memory entails the capacity even after long delays (Bauer et al., 2000; Simcock and to encode, store, and retrieve an event, in conjunction Hayne, 2003). The ability to retrieve specific episodes con- with contextual content associated with that event (e.g., tinues to improve during middle childhood (e.g., Brainerd “I met Sophia last week at Jake’s party”). Extant models of et al., 2004; Ghetti and Angelini, 2008; Ghetti et al., 2011; memory have demonstrated that episodic memory can be Schneider et al., 2002). In this review we focus on middle differentiated functionally (e.g., Yonelinas, 2002) and neu- childhood, which corresponds roughly to the elementary rologically (Eichenbaum et al., 2007) from other forms of school years. explicit memory. For example, recollecting an episode is Children’s episodic memory is assessed in a number different from recognizing a past event on the basis of its of ways, for example with tasks that require participants familiarity; indeed, familiarity enables us to quickly expe- to recall associations between events and the context in rience an event as being part of our past in the absence of which they occurred (DeMaster and Ghetti, in press; Lloyd memory for context (e.g., “I met this person before, but can’t et al., 2009; Piolino et al., 2007). For example, children remember when or where”). Episodic memory supports may be required to memorize objects presented with back- daily acts such as remembering where one has placed her grounds of varying colors and they may be later asked keys or whether one has already taken a pill that day. Fur- to determine whether or not objects have been previ- thermore, it provides the foundation for autobiographical ous viewed and, if viewed, with what border color they memory (Nelson and Fivush, 2004) and contributes to the were presented (Fig. 1). In some tasks, it is possible to sense of continuity of self over time (Buckner and Carroll, assess the contribution of episodic recollection to perfor- 2007). mance, by either asking to participants to characterize their The implications of healthy episodic memory devel- subjective memory experience as recollection or famil- opment are far-reaching. Recent evidence indicates that iarity (Billingsley et al., 2002; Piolino et al., 2007) or by episodic recollection of ideas, and not a generalized sense using estimation methods that tease apart the contribution of familiarity for them, is preferentially involved in reading of episodic recollection from that of familiarity (Brainerd comprehension because it supports the ability to integrate et al., 2004; Ghetti and Angelini, 2008). ideas from the text during retrieval (Mirandola et al., 2011). The robust improvement of episodic memory observed Furthermore, measures of episodic memory are part of during middle childhood in these studies may be explained standardized assessments of intellectual ability (Woodcock by a number of factors. There is extensive evidence of and Johnson, 1989). Thus, episodic memory has broad more frequent and efficient use of strategies based on implications for learning and associated positive outcomes. semantic organization as well as increased sophistication Finally, the development of episodic memory is of strategies used to regulate memory accuracy (e.g., Ghetti impaired following mild forms of neurological insult due and Alexander, 2004; Ghetti et al., 2010a; Ornstein et al., to cerebral hypoxia or ischemia (e.g., De Haan, 2012; 2006; Schwenk et al., 2007; for a review see Bjorklund Ghetti et al., 2010c), or traumatic brain injury (e.g., Hanten et al., 2009). Furthermore, age-related differences are more et al., 2004). Episodic memory is also impaired in sev- pronounced when the testing situation imposes greater eral disorders, including depression (Backman and Forsell, retrieval demands, suggesting improvement in the abil- 1994; Whalley et al., 2009), post-traumatic stress disor- ity to conduct memory searches (e.g., Gee and Pipe, 1995; der (PTSD; Moradi et al., 2008; Vasterling et al., 2009), Hasselhorn, 1990; Paz-Alonso et al., 2009). Finally, there is a anxiety (Airaksinen et al., 2005), schizophrenia (Heinrichs wealth of evidence indicating that memory improvements and Zakzanis, 1998; Ragland et al., 2003), and Fragile X are in part explained by the development of metacognitive Syndrome (Ornstein et al., 2008). In some cases, episodic operations, which are involved in monitoring and control- memory deficits emerge in childhood and precede the ling memory encoding and retrieval (DeMarie and Ferron, onset of the disorder (e.g., schizophrenia; Erlenmeyer- 2003; Ghetti, 2008; Ghetti et al., 2010a; Roebers et al., Kimling et al., 2000), and may be thus considered an 2009). In this vein, it has been shown that, from age 6 to endophetotypic marker of the disorder (Gottesman and 17, subjective assessments of episodic memory quality are Gould, 2003). increasingly relied upon to make decisions, even though Given the centrality of episodic memory for human cog- these assessments track actual episodic memory accurately nition, as well as its susceptibility to impairment across an across ages (Ghetti et al., 2011). array of neurological and psychiatric disorders, it is criti- Importantly, it should be noted that improvements over cal to understand the fundamental mechanisms underlying middle childhood are not evident across all forms of explicit its typical development.