Effects of study task on the neural correlates of source encoding

Abstract

The present study investigated whether the neural correlates of source memory vary according to study task. Subjects studied visually presented words in one of two background contexts. In each test, subjects made old/new recognition and source memory judgments. In one study test cycle, study words were subjected to animacy judgments, whereas in another cycle the study task required syllable judgments. Functional magnetic resonance imaging (fMRI) was employed to contrast the neural activity elicited by study words that attracted accurate source judgments on the later memory test, as opposed to words for which source judgments were incorrect or for which source information was unavailable. In both tasks, relative to words for which source memory failed, study words that were later assigned to the correct source elicited enhanced activity in ventral extrastriate cortex. In addition to these common effects of subsequent source memory, additional effects were observed that were selective for each study task. The present findings add weight to the proposal that neural activity supporting successful episodic memory encoding is a reflection of both the online processing engaged by an episode as it is experienced, and the demands imposed by the later retrieval task.

Differential effects of semantic processing on memory encoding

“…Both findings suggest that in this task the level of difficulty (or more generally time of processing during encoding) influenced memory encoding: Words that required longer processing and more often led to mistakes showed a tendency to be remembered better. Similar findings have been reported before [Duverne et al, 2009;Uncapher and Rugg, 2005;Wagner et al, 1998], but there are also several studies that did not produce such an effect Park et al, 2008]. It might mean that for the animacy decision task, part of the SMEs seen in the fMRI analysis is a consequence of more demanding processing as a function of task difficulty.…”

“…that specific brain regions show SMEs for one task but not another. This has been demonstrated for the task contrasts animacy judgments versus syllable counting [Otten et al, 2002;Park et al, 2008], processing of meaning versus shape of words [Fletcher et al, 2002], and social versus nonsocial judgments [Mitchell et al, 2004]. These findings suggest that different study tasks may contribute to memory encoding by engaging different neural systems.…”

“…Most studies so far have induced semantic processing by having subjects complete categorization tasks such as living versus nonliving Park et al, 2008] or concrete versus abstract [Baker et al, 2001;Wagner et al, 1998] decisions. To solve tasks like these, the subject has to retrieve rather abstract information from semantic knowledge.…”

A new semantic list learning task to probe functioning of the Papez circuit

“…This promotes more consistent memory performance by minimizing individual variability in the contributions of executive functioning (STM) to subsequent recall (Bermingham, Hill, Woltz, & Gardner, 2013). Semantic organization and processing strategies are also consistent with deeper encoding and more robust hippocampal activation (Craik and Lockhart, 1972; Flegal, Marín-Gutiérrez, Ragland, & Ranganath, 2014; Fliessbach, Buerger, Trautner, Elger, & Weber, 2010; Otten, Henson, & Rugg, 2001; Park, Uncapher, & Rugg, 2008; Woodard et al, 2005). We sought to further enhance the clinical utility of the current paradigm by including a behavioral measure of subsequent memory in which a wide range of performance is possible, thereby ensuring the sensitivity of our task to memory impairments.…”

The role of spatial attention during spatial encoding

“…Subsequent memory studies have also investigated the neural regions associated with the encoding of spatial information (Cansino, Maquet, Dolan, & Rugg, 2002;Park, Uncapher, & Rugg, 2008;Ross & Slotnick, 2008;Uncapher et al, 2006;Uncapher & Rugg, 2009; see also, Sommer, Rose, Gläscher, Wolbers, & Bϋchel, 2005). During the encoding phase in these studies, participants were presented with items in different spatial locations.…”