What Makes Deeply Encoded Items Memorable? Insights into the Levels of Processing Framework from Neuroimaging and Neuromodulation

Abstract

When we form new memories, their mnestic fate largely depends upon the cognitive operations set in train during encoding. A typical observation in experimental as well as everyday life settings is that if we learn an item using semantic or “deep” operations, such as attending to its meaning, memory will be better than if we learn the same item using more “shallow” operations, such as attending to its structural features. In the psychological literature, this phenomenon has been conceptualized within the “levels of processing” framework and has been consistently replicated since its original proposal by Craik and Lockhart in 1972. However, the exact mechanisms underlying the memory advantage for deeply encoded items are not yet entirely understood. A cognitive neuroscience perspective can add to this field by clarifying the nature of the processes involved in effective deep and shallow encoding and how they are instantiated in the brain, but so far there has been little work to systematically integrate findings from the literature. This work aims to fill this gap by reviewing, first, some of the key neuroimaging findings on the neural correlates of deep and shallow episodic encoding and second, emerging evidence from studies using neuromodulatory approaches such as psychopharmacology and non-invasive brain stimulation. Taken together, these studies help further our understanding of levels of processing. In addition, by showing that deep encoding can be modulated by acting upon specific brain regions or systems, the reviewed studies pave the way for selective enhancements of episodic encoding processes.

Dynamic changes in prefrontal cortex involvement during verbal episodic memory formation

“…A discrepancy exists however between fMRI and TMS studies. fMRI studies have consistently shown an engagement of the left VLPFC, especially when the encoding task involves semantic processing (Fletcher, Shallice & Dolan, 1998;Blumenfeld & Ranganath, 2007;Galli, 2014), whereas only few studies reported DLPFC activations (Savage et al, 2001;Blumenfeld & Ranganath, 2006). On the contrary, most TMS and tDCS studies of episodic memory found an effect of left DLPFC stimulation on subsequent retrieval (Rossi et al, 2001(Rossi et al, , 2004(Rossi et al, , 2006(Rossi et al, , 2011Epstein, Sekino, Yamaguchi, Kamiya & Ueno, 2002;Sandrini, Cappa, Rossi, Rossini & Miniussi, 2003;Skrdlantová et al, 2005;Turriziani et al, 2008;Turriziani, Smirni, Oliveri, Semenza & Cipolotti, 2010;Elmer, Burkard, Renz, Meyer & Jancke, 2009;Gagnon, Schneider, Grondin & Blanchet, 2010;Innocenti et al, 2010;Javadi, Cheng & Walsh, 2012;Javadi & Cheng, 2013;Manenti, Brambilla, Petesi, Ferrari & Cotelli, 2013) whereas only a few targeted the left VLPFC (Floel et al, 2004;Köhler et al, 2004;Kahn et al, 2005;Machizawa et al, 2010;Blumenfeld et al, 2014;Vidal-Pinero et al, 2014).…”

A Systematic Review on the Conceptualization and Operationalization of Students' Levels of Processing in Functional Magnetic Resonance Imaging Studies

“…Concerning the type of deep and surface processing, a variety of encoding tasks were defined in these studies (Table ). Following the systematic review of Galli (), these encoding tasks can be ordered along a semantic‐structural axis. Deep levels of processing fall under the semantic part and surface levels of processing under the structural part, but some tasks are located at the intermediate level along the semantic‐structural axis (Galli, ).…”

“…Following the systematic review of Galli (), these encoding tasks can be ordered along a semantic‐structural axis. Deep levels of processing fall under the semantic part and surface levels of processing under the structural part, but some tasks are located at the intermediate level along the semantic‐structural axis (Galli, ). With regard to deep levels of processing, previous reviews indicated that animacy judgment tasks need a semantic analysis (Binder, Desai, Graves, & Conant, ; Galli, ).…”

“…A recent review of Galli () focused on summarizing the neural correlates of deep and surface processing in functional magnetic resonance imaging (fMRI) and event‐related potentials (ERP) research. This review indicated that there is a great variety in tasks that were used to measure deep and surface processing.…”

“…In memory research, the subsequent memory paradigm is mostly used (Cabeza & Nyberg, ), in which participants are presented with items that they need to remember and the brain‐imaging data are later analyzed as a function of whether the items were remembered or forgotten during a memory test ( Gazzaniga, Ivry, & Mangun, ). Whether a word or word pair will be remembered or not not only depends on the levels of processing used, but also on the way the memory is probed (Craik & Lockhart, ; Galli, ; Morris, Bransford, & Franks, ; Tulving & Thompson, ). In addition, when levels of processing are investigated at the text level, recall measures have a stronger relationship with surface levels of processing, such as memorizing the text, than with deep levels of processing, such as trying to understand the underlying meaning of the text (Dinsmore & Alexander, ).…”