Schema Representation in Patients with Ventromedial PFC Lesions

Abstract

Human neuroimaging and animal studies have recently implicated the ventromedial prefrontal cortex (vmPFC) in memory schema, particularly in facilitating new encoding by existing schemas. In humans, the most conspicuous memory disorder following vmPFC damage is confabulation; strategic retrieval models suggest that aberrant schema activation or reinstatement plays a role in confabulation. This raises the possibility that beyond its role in schema-supported memory encoding, the vmPFC is also implicated in schema reinstatement itself. If that is the case, vmPFC lesions should lead to impaired schema-based operations, even on tasks that do not involve memory acquisition. To test this prediction, ten patients with vmPFC damage, four with present or prior confabulation, and a group of twelve matched healthy controls made speeded yes/no decisions as to whether words were closely related to a schema (a visit to the doctor). Ten minutes later, they repeated the task for a new schema (going to bed) with some words related to the first schema included as lures. Last, they rated the degree to which stimuli were related to the second schema. All four vmPFC patients with present or prior confabulation were impaired in rejecting lures and in classifying stimulus belongingness to the schema, even when they were not lures. Nonconfabulating patients performed comparably to healthy adults with high accuracy, comparable reaction times, and similar ratings. These results show for the first time that damage to the human vmPFC, when associated with confabulation, leads to deficient schema reinstatement, which is likely a prerequisite for schema-mediated memory integration.

Hippocampal–medial prefrontal circuit supports memory updating during learning and post-encoding rest

“…Subgenual MPFC exhibits a widespread pattern of anatomical connectivity (Barbas and Blatt, 1995; Cavada et al, 2000; Ongür and Price, 2000), allowing it to integrate across limbic inputs during learning. Damage to this region results in reduced false memory formation (Warren et al, 2014) and poor schema representation (Ghosh et al, 2014), suggesting its involvement in integrating across sources of information. Engagement of subgenual MPFC also increases with consolidation (Nieuwenhuis and Takashima, 2011), perhaps tracking the increasing importance of abstracted neocortical representations as experiences become more remote.…”

Episodic future thinking: mechanisms and functions

“…However, there were also other important differences between the aforementioned studies, such as center of lesion overlap, etiology, and amnesic status of the patients. Nonetheless, the pattern suggests that the vmPFC supports access to schemata or conceptual knowledge of the respective scenarios that then foster the ability to construct specific episodes (101; see also 103). Consistent with this interpretation, fMRI data indicate that the vmPFC particularly supports simulations that can draw on rich knowledge (99) and that a more dorsal part of the mPFC is similarly more strongly engaged during simulations of episodes that are part of the same event cluster (42).…”

Differences in the neural signature of remembering schema-congruent and schema-incongruent events

“…The mPFC is suggested to achieve this via influencing memory processing in the limbic system, especially in the HC, supposedly through inhibitory connections (Bein et al, 2014;Navawongse and Eichenbaum, 2013;Nieuwenhuis and Takashima, 2011;Schlichting and Preston, 2015;Wang and Morris, 2010). Evidence for this claim comes from recent studies with patients suffering from lesions in the ventral mPFC (Ghosh et al, 2014;Warren et al, 2014). Compared to control patients, patient with ventral mPFC lesions displayed less schema-reinstatement (Ghosh et al, 2014) and less schema-related memory intrusions in the Deese-Roediger-McDermott (DRM) paradigm (Warren et al, 2014), which suggests that an intact mPFC would increase the weight of schema-congruent memories.…”

“…Evidence for this claim comes from recent studies with patients suffering from lesions in the ventral mPFC (Ghosh et al, 2014;Warren et al, 2014). Compared to control patients, patient with ventral mPFC lesions displayed less schema-reinstatement (Ghosh et al, 2014) and less schema-related memory intrusions in the Deese-Roediger-McDermott (DRM) paradigm (Warren et al, 2014), which suggests that an intact mPFC would increase the weight of schema-congruent memories. Further support is provided by animal models, in which inhibition of the mPFC has been found to impair memory retrieval (Tse et al, 2011).…”