The relationship between task‐related and subsequent memory effects

Abstract

The primary aim of this fMRI study was to assess the proposal that negative subsequent memory effects – greater activity for later forgotten relative to later remembered study items – are localized to regions demonstrating task-negative effects, and hence to potential components of the default mode network. Additionally, we assessed whether positive subsequent memory effects overlapped with regions demonstrating task-positive effects. Eighteen participants were scanned while they made easy or difficult relational judgments on visually presented word pairs. Easy and hard task blocks were interleaved with fixation-only rest periods. In the later unscanned test phase, associative recognition judgments were required on intact word pairs (studied pairs), rearranged pairs (pairs formed from words presented on different study trials) and new pairs. Subsequent memory effects were identified by contrasting the activity elicited by study pairs that went on to be correctly endorsed as intact versus incorrectly endorsed as rearranged. Task effects were identified by contrasting all study items and rest blocks. Both task-negative and task-positive effects were evident in widespread cortical regions and negative and positive subsequent memory effects were generally confined to task-negative and task-positive regions respectively. However, subsequent memory effects could be identified in only a fraction of task-sensitive voxels and, unlike task effects, were insensitive to the difficulty manipulation. The findings for the negative subsequent memory effects are consistent with recent proposals that the default mode network is functionally heterogeneous, and suggest that these effects are not accurately characterized as reflections of the modulation of the network as a whole.

Sensitivity of negative subsequent memory and task-negative effects to age and associative memory performance

“…Across studies employing a variety of different study tasks and memory tests, negative subsequent memory effects have consistently been reported to be attenuated (and sometimes reversed) in healthy older individuals (e.g., de Chastelaine et al 2011; Duverne et al, 2009; Gutchess et al, 2005; Mattson et al, in press; Miller et al 2008; Mormino et al 2012; Park et al, 2013). Furthermore, the magnitude of negative subsequent memory effects in older adults has been reported to correlate positively with their memory performance (de Chastelaine et al, 2011; Mattson et al, in press; Miller et al, 2008; Mormino et al, 2012; see de Chastelaine and Rugg, 2014, for similar findings in young individuals), suggesting that the effects reflect the engagement of processes that are of functional significance for memory encoding.…”

“…Notably, the effects are typically found in only a small subset of task-negative regions (e.g., de Chastelaine & Rugg, 2014). Moreover, negative subsequent memory effects can also be identified in ‘task-positive’ regions that are not part of the default mode network.…”

“…For example, Daselaar et al (2004) and Mattson et al (in press) both described robust negative subsequent memory effects in the anterior insula, despite the fact that the region exhibited a marked task-positive response with respect to baseline (see also Reynolds et al, 2004, Wagner and Davachi, 2001). Furthermore, it was recently reported that task-negative and negative subsequent memory effects can be dissociated by manipulation of the difficulty of the study task (de Chastelaine & Rugg, 2014): Whereas the former effects were enhanced in the more difficult condition, difficulty had no effect on the magnitude of the negative subsequent memory effects elicited in the same brain regions. Together, these findings suggest that negative subsequent memory effects reflect processes additional to those reflected in task-induced modulations of the default mode network.…”

“…We employed the same combination of study task and subsequent associative recognition test that was used by de Chastelaine et al, (2011). This and similar experimental procedures have consistently been reported to elicit robust and widespread negative subsequent memory effects in young adults (e.g., de Chastelaine and Rugg, 2014; de Chastelaine et al, 2011; Daselaar et al, 2004; Park and Rugg, 2008) and are highly sensitive to increasing age (e.g., Bender et al, 2010; Salthouse, 2009). Here, we went beyond our prior study (de Chastelaine et al, 2011) in two ways.…”

A parietal memory network revealed by multiple MRI methods

“…Such effects tend to come in two forms: regions are either more active, relative to baseline, for subsequently forgotten items than for subsequently remembered items, or else they show greater deactivation, relative to baseline, for the successfully remembered items. PMN regions, as well as some DMN regions, show the latter pattern [42][43][44].…”