Differential roles for medial prefrontal and medial temporal cortices in schema-dependent encoding: From congruent to incongruent

Abstract

Information that is congruent with prior knowledge is generally remembered better than incongruent information. This effect of congruency on memory has been attributed to a facilitatory influence of activated schemas on memory encoding and consolidation processes, and hypothesised to reflect a shift between processing in medial temporal lobes (MTL) towards processing in medial prefrontal cortex (mPFC). To investigate this shift, we used functional magnetic resonance imaging (fMRI) to compare brain activity during paired-associate encoding across three levels of subjective congruency of the association with prior knowledge. Participants indicated how congruent they found an object-scene pair during scanning, and were tested on item and associative recognition memory for these associations one day later. Behaviourally, we found a monotonic increase in memory performance with increasing congruency for both item and associative memory. Moreover, as hypothesised, encoding-related activity in mPFC increased linearly with increasing congruency, whereas MTL showed the opposite pattern of increasing encoding-related activity with decreasing congruency. Additionally, mPFC showed increased functional connectivity with a region in the ventral visual stream, presumably related to the binding of visual representations. These results support predictions made by a recent neuroscientific framework concerning the effects of schema on memory. Specifically, our findings show that enhanced memory for more congruent information is mediated by the mPFC, which is hypothesised to guide integration of new information into a pre-existing schema represented in cortical areas, while memory for more incongruent information relies instead on automatic encoding of arbitrary associations by the MTL.

Schema-conformant memories are preferentially consolidated during REM sleep

“…On the other hand, consolidation-related theta power in frontal areas, and the fact that the results point consistently towards a specific role for REM sleep and not SWS, may appear strange at first glance, and at odds with the standard model of consolidation. However, a recent series of studies by van Kesteren et al (van Kesteren, Rijpkema, et al, 2010;van Kesteren et al, 2013; looking at the neural mechanisms underpinning the consolidation of schema-conformant items, suggest a possible modification of the standard model to take into account how well new memories fit with existing schemata, with tightly linked memories following a more rapid consolidation path.…”

“…Once again, they also observed an important role for the mPFC, in this case an enhanced coupling between mPFC and somatosensory cortex (implicated in memory for the fabric). The final study by van Kesteren et al (van Kesteren et al, 2013) used a similar but slightly simplified congruency paradigm, in this case directly looking at object-scene pairings which were congruent or not, with functional neuroimaging of retrieval. This study once again revealed an enhanced role for the mPFC for schema-dependent items, and also found a decreased role for the hippocampus for these items.…”

“…In a series of recent studies, van Kesteren and colleagues (van Kesteren, Rijpkema, Ruiter, & Fernández, 2010;van Kesteren et al, 2013; have attempted to elucidate the mechanisms underlying this, and have confirmed that the medial prefrontal cortex (mPFC) appears to at least partly take over the hippocampal binding role for schema-conformant items.…”

False Recall Is Reduced by Damage to the Ventromedial Prefrontal Cortex: Implications for Understanding the Neural Correlates of Schematic Memory

“…Moreover, the vmPFC is anatomically (Ongür and Price, 2000;Saleem et al, 2008) and functionally (Ranganath et al, 2005;AndrewsHanna et al, 2010) connected with MTL regions supporting memory. Reflecting that connectivity, vmPFC (or a homologous region) is activated when schematic or contextual memory is exercised as shown in animal models (Euston and McNaughton, 2006;Tse et al, 2007Tse et al, , 2011 and neuroimaging studies (Kumaran et al, 2009;van Kesteren et al, 2010;Bonnici et al, 2012;Zeithamova et al, 2012a). In this context, it is notable that severe declarative memory impairments after vmPFC damage are uncommon (Janowsky et al, 1989;Stuss et al, 1994), although damage to vmPFC (sometimes extending to surrounding regions) may increase confabulation and false recognition (DelbecqDerouesné et al, 1990;Umeda and Kato, 2000;Umeda et al, 2001;Gilboa et al, 2006).…”

“…A recent proposal (van Kesteren et al, 2012) suggested that medial prefrontal cortex (PFC) plays a critical role for new memories that overlap with existing knowledge, effectively weighting the influence of schematic memory. For example, increasing the weight of schematically related memories when recalling words fitting a "winter" schema would increase the probability of recalling the nonstudied word "snow" (as in the DRM paradigm).…”