What makes deeply encoded items memorable? Insights into the levels of processing framework from neuroimaging and neuromodulation.

Giulia Galli

doi:10.3389/fpsyt.2014.00061

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.

Highlights

Whether we remember an event or not depends on a set of mental processes and brain mechanisms that occur during the initial encoding of the event, its subsequent retrieval, and consolidation processes that take place between encoding and retrieval
As evidenced by a post-Transcranial magnetic stimulation (TMS) Functional magnetic resonance imaging (fMRI) scan, theta burst stimulation (TBS) increased activations of the left ventrolateral prefrontal cortex (PFC), occipital cortex, and cerebellum, and the connectivity between these brain regions, while volunteers were performing the deep encoding task. These findings suggest that the combination of neuroimaging and brain stimulation offers relevant insights into the brain networks involved in levels of processing (LOP) effects, even in the absence of overt behavioral effects
The findings discussed here provide partial answers to the question of “what makes deeply encoded items more memorable?” They suggest that memory formation for deeply encoded events is enhanced when the products of online, task-specific processing are integrated with pre-existing knowledge about the event into a coherent episodic memory trace

Summary

Giulia Galli *

Brain Investigation and Neuromodulation (BIN) Laboratory, Azienda Ospedaliera Universitaria Senese, Siena, Italy. When we form new memories, their mnestic fate largely depends upon the cognitive operations set in train during encoding. 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.

INTRODUCTION

CONCLUSION