Neural mechanisms underlying prospective memory

There are several current projects addressing how the PFC subserves strategic processing, using converging behavioral, computational, and functional neuroimaging techniques. One overarching hypothesis is that different cognitive strategies may be associated with the same underlying processes and mechanisms, but that the ordering of the recruitment of such processes directly determines the observed strategy.

For example, we can “proactively” prepare to respond to an upcoming situation by actively maintaining a current set of rules in response to an environmental cue. A common example of such a strategy decision is prospective memory, or more specifically, trying to remember to pick up a carton of orange juice on the way home.

One strategy to perform this task would be to actively maintain and rehearse “pick up orange juice on the way home” from the moment you notice you are out of orange juice to the moment you are at the appropriate intersection on the way home. This is clearly disadvantageous, as it would interfere with everything else that needed to be cone throughout the day. An alternative strategy would be to encode a set of appropriate retrieval cues at the moment you notice you need orange juice, and simply recall the appropriate actions when you encounter those retrieval cues (e.g. the appropriate intersection).

Current neuroimaging and behavioral experiments are focused at understanding when various types of strategies are utilized, and what brain mechanisms may be critical for each.

Understanding the functional organization of prefrontal cortex

To investigate the quesion of how different areas of PFC contribute to cognitive control, we have focused on understanding the differences between anterior PFC (aPFC) and lateral PFC. The functional organization of PFC is a critical question remaining in the field of cognitive neuroscience, and there are many competing hypotheses regarding the dimensions that underlie its organization.

For example, whereas lateral PFC has been widely implicated as being critical for the active maintenance of task goals that bias the selection of an appropriate response, the hypothesized role of aPFC is much more controversial. One hypothesis is based on the observation that many of our behaviors have a hierarchical structure: we must often hold onto one high-level goal (e.g. “solve the math problem”) while other subgoals are being completed (e.g. carrying and adding numbers while solving a multiplication problem).

Based on this hypothesis, we have proposed that aPFC subserves the general maintenance of high-level goal information in working memory while other subgoal-related information is processed by more posterior areas of lateral PFC. We have identified activity in aPFC that is consistent with such an interpretation within task-switching (Braver, Reynolds, & Donaldson, 2003), prospective memory (Reynolds, West, & Braver, 2008), and episodic encoding and memory paradigms (Reynolds, McDermott, & Braver, 2006).

In addition to identifying a central role for aPFC in implementing higher-level goals, these studies have also illuminated some of the key differences between aPFC and lateral PFC. Consistent with our hypotheses, these data suggest that lateral PFC may be maintaining information that is directly relevant to selecting a response on a trial-to-trial basis, but that aPFC may be maintaining more abstract representations that are needed for longer time periods. Current work attempts to extend this work by determining the minimal conditions required to recruit aPFC.

Major Depressive Disorder and Reward Learning

This study analyzes reward processing behavior in women both with and without Major Depressive Disorder (MDD). The purpose of this research is to examine whether differences in reward responses relate to the psychological underpinnings of MDD. Previous research has implicated reward processing abnormalities in MDD. We plan to use fMRI scanning to investigate whether there are differences in brain activation patterns when completing a reward learning task amongst the different groups.

We are currently recruiting participants for this study.  If you are interested in learning more or participating, please contact us!

Participants must meet the following characteristics.  All participants must be:

• female;
• 18-45 years old;
• right handed;
• a native English speaker; AND
• neurologically healthy

In addition, participants must fit into one of two groups: