Our lab studies several neocortical contributions to episodic memory and decision-making using a variety of techniques, including functional magnetic resonance imaging (fMRI), event-related potentials (ERP), transcranial magnetic stimulation (TMS), and patient studies. These studies range from investigations into prefrontal and parietal cortex activity associated with shifts in decision criteria to attempts to uncover the sources variability of individual patterns of brain activity during an episodic memory task. Ultimately, our goal is to use these neuroscientific studies to understand the processes of the mind when remembering a past event, and to appreciate the uniqueness of these processes at the individual level.

Criterion Shifting in Recognition Memory

Miller Lab Criterion Shifting Research

A critical aspect of recognition memory involves weighing the available evidence (i.e., ecphory or the product of retrieval) against a decision criterion. The placement of a criterion can be affected by a number of factors (e.g., the probability of a target), and changes in those factors can cause subjects to shift their criteria. In the past, we have used criterion shift models to explain the high false alarm rate in the DRM false memory paradigm. More recently, we have observed that while some individuals will shift their criterion to an optimal degree, others will not shift at all. We have been exploring the inherent characteristics that seem to mediate an individual's willingness to shift a decision criterion. Further, we have exploited these individual differences in criterion shifting in order to better understand the fronto-parietal network of brain activity associated with successful memory.
Members involved: Justin Kantner, Brian Lopez, and Ben Turner

Hypothesis Formation and Evaluation

Miller Lab Research Summary

Areas in white denote regions associated with hypothesis formation and evaluation in healthy individuals.

One of the hallmarks of split-brain research is the left hemisphere's drive to interpret the world around it. Our goal is to understand and characterize this need of the human brain to form hypotheses. Specifically, we want to determine what propels an individual to seek an explanation, how hypotheses are generated, and what constitutes a good explanation. We are also interested in how the brain evaluates the plausibility and validity of its hypotheses. We believe the brains of healthy individuals strike a balance between hypothesis formation and evaluation, and a perturbation in this system may give rise to delusional disorders. Our ultimate goal is to uncover the neural processes that support hypothesis formation and evaluation in both healthy and deluded individuals.
Members involved: Nikki Marinsek and Ben Turner

Individual Variability in Brain Activity

Miller Lab Research Summary

Brain activity associated with memory retrieval for nine individuals. Notice the variability between individual brain maps.

Neuroimaging studies typically rely on maps of brain activity that are an average across a group of subjects in order to increase statistical power. However, our studies have demonstrated that an individual map of brain activity is not unlike a fingerprint in its uniqueness and relatively stability over time, and a reliance on group maps can leave out a wealth of information at the individual level. We seek to understand the sources of this variability in brain activity given the variable and dynamic nature of episodic memory.
Members involved: Ben Turner and Brian Lopez

Partietal Contributions to Memory

Miller Lab Research Summary

Parietal lobe activations are a ubiquitous finding in neuroimaging studies of recognition memory, but the functionality of this region remains a mystery. We have explored this functionality using a variety of source monitoring tasks and by manipulating decision processes during recognition memory tasks.
Members involved: Amy Frithsen

Split Brain Research

Miller Lab Split Brain Research

Our lab also conducts studies of patients that have had their corpus callosum severed due to severe epilepsy. These patients present a unique opportunity to understand the functioning of each hemisphere in isolation and the effect of severing inter-hemispheric communication. These studies have ranged in topics from episodic memory to probability matching to moral reasoning.

Social Reasoning & Theory of Mind

Miller Lab Social Reasoning Research

In the real world, decision-making and reasoning usually occurs within a social context. We have worked on neuroimaging and patient studies that have examine this issue with a consideration of specialized modules responsible for theory of mind attributions (that is, attributing beliefs and thoughts to other people).