Contributions Of the Human Medial Prefrontal Cortex To Associative Recognition Memory: Evidence From Functional Neuroimaging

Neuroimaging studies of episodic memory, or memory of events from our personal past, have predominantly focused their attention on medial temporal lobe (MTL). There is growing acknowledgement however, from the cognitive neuroscience of memory literature, that regions outside the MTL can support episodic memory processes. The medial prefrontal cortex is one such region garnering increasing interest from researchers. Using behavioral and functional magnetic resonance imaging measures, over two studies, this thesis provides evidence of a mnemonic role of the medial PFC. In the first study, participants were scanned while judging the extent to which they agreed or disagreed with the sociopolitical views of unfamiliar individuals. Behavioral tests of associative recognition revealed that participants remembered with high confidence viewpoints previously linked with judgments of strong agreement/disagreement. Neurally, the medial PFC mediated the interaction between high-confidence associative recognition memory and beliefs associated with strong agree/disagree judgments. In an effort to generalize this finding to well-established associative information, in the second study, we investigated associative recognition memory for real-world concepts. Object-scene pairs congruent or incongruent with a preexisting schema were presented to participants in a cued-recall paradigm. Behavioral tests of conceptual and perceptual recognition revealed memory enhancements arising from strong resonance between presented pairs and preexisting schemas. Neurally, the medial PFC tracked increases in visual recall of schema-congruent pairs whereas the MTL tracked increases in visual recall of schema-incongruent pairs. Additionally, ventral areas of the medial PFC tracked conceptual components of visual recall specifically for schema-congruent pairs. These findings are consistent with a recent theoretical proposal of medial PFC contributions to memory for schema-related content. Collectively, these studies provide evidence of a role for the medial PFC in associative recognition memory persisting for associative information deployed in our daily social interactions and for those associations formed over multiple learning episodes. Additionally, this set of findings advance our understanding of the cognitive contributions of the medial PFC beyond its canonical role in processes underlying social cognition.

Supplementary Eye Fields

The supplementary eye fields (SEFs) are located in dorsomedial frontal cortex and contribute to high-level control of eye movements. Recordings in the SEF reveal neural activity related to vision, saccades, and fixations, and electrical stimulation in the SEF evokes saccades and fixations. Inactivations and lesions of the SEF, however, cause minimal oculomotor deficits. The SEF thus processes information relevant to eye movements and influences critical oculomotor centers but seems unnecessary for generating action. Instead, the SEF has overarching, subtle functions that include limb-eye coordination, the timing and sequencing of actions, learning, monitoring conflict, prediction, supervising behavior, value-based decision making, and the monitoring of decisions.

Supplementary Eye Fields

The supplementary eye fields (SEFs) are located in dorsomedial frontal cortex and contribute to high-level control of eye movements. Recordings in the SEF reveal neural activity related to vision, saccades, and fixations, and electrical stimulation in the SEF evokes saccades and fixations. Inactivations and lesions of the SEF, however, cause minimal oculomotor deficits. The SEF thus processes information relevant to eye movements and influences critical oculomotor centers but seems unnecessary for generating action. Instead, the SEF has overarching, subtle functions that include limb-eye coordination, the timing and sequencing of actions, learning, monitoring conflict, prediction, supervising behavior, value-based decision making, and the monitoring of decisions.

Individual Differences in the Neural Response to Personal Goal Pursuit Success and Failure: A Developmental Analysis

Regulatory focus theory (RFT) proposes two different social-cognitive motivational systems for goal pursuit: a promotion system, which is organized around strategic approach behaviors and "making good things happen," and a prevention system, which is organized around strategic avoidance and "keeping bad things from happening." The promotion and prevention systems have been extensively studied in behavioral paradigms, and RFT posits that prolonged perceived failure to make progress in pursuing promotion or prevention goals can lead to ineffective goal pursuit and chronic distress (Higgins, 1997).

Research has begun to focus on uncovering the neural correlates of the promotion and prevention systems in an attempt to differentiate them at the neurobiological level. Preliminary research suggests that the promotion and prevention systems have both distinct and overlapping neural correlates (Eddington, Dolcos, Cabeza, Krishnan, & Strauman, 2007; Strauman et al., 2013). However, little research has examined how individual differences in regulatory focus develop and manifest. The development of individual differences in regulatory focus is particularly salient during adolescence, a crucial topic to explore given the dramatic neurodevelopmental and psychosocial changes that take place during this time, especially with regard to self-regulatory abilities. A number of questions remain unexplored, including the potential for goal-related neural activation to be modulated by (a) perceived proximity to goal attainment, (b) individual differences in regulatory orientation, specifically general beliefs about one's success or failure in attaining the two kinds of goals, (c) age, with a particular focus on adolescence, and (d) homozygosity for the Met allele of the catechol-O-methyltransferase (COMT) Val158Met polymorphism, a naturally occurring genotype which has been shown to impact prefrontal cortex activation patterns associated with goal pursuit behaviors.

This study explored the neural correlates of the promotion and prevention systems through the use of a priming paradigm involving rapid, brief, masked presentation of individually selected promotion and prevention goals to each participant while being scanned. The goals used as priming stimuli varied with regard to whether participants reported that they were close to or far away from achieving them (i.e. a "match" versus a "mismatch" representing perceived success or failure in personal goal pursuit). The study also assessed participants' overall beliefs regarding their relative success or failure in attaining promotion and prevention goals, and all participants were genotyped for the COMT Val158Met polymorphism.

A number of significant findings emerged. Both promotion and prevention priming were associated with activation in regions associated with self-referential cognition, including the left medial prefrontal cortex, cuneus, and lingual gyrus. Promotion and prevention priming were also associated with distinct patterns of neural activation; specifically, left middle temporal gyrus activation was found to be significantly greater during prevention priming. Activation in response to promotion and prevention goals was found to be modulated by self-reports of both perceived proximity to goal achievement and goal orientation. Age also had a significant effect on activation, such that activation in response to goal priming became more robust in the prefrontal cortex and in default mode network regions as a function of increasing age. Finally, COMT genotype also modulated the neural response to goal priming both alone and through interactions with regulatory focus and age. Overall, these findings provide further clarification of the neural underpinnings of the promotion and prevention systems as well as provide information about the role of development and individual differences at the personality and genetic level on activity in these neural systems.