As we move through the
world, our past experiences enable us to set expectations,
build simulations of what might happen next, and plan
actions. Past experience also helps us to interpret complex
social interactions where much of our understanding comes
from parallels to remembered situations and mental
simulation of the possible intent and future actions of
Our ability to use past experience to flexibly anticipate upcoming situations depends on a complex interplay between memory systems, executive control systems, and other information processing systems of the brain. Our laboratory is focused on a range of questions that all surround understanding how brain systems enable us to benefit from past experience and how these systems change during development and aging. Some of the specific questions that presently drive our research include:
What are the neural pathways that encode and retrieve information about the past? Brain systems have evolved to capture the contents of experience including the recurring regularities in the world as well as the arbitrary associations that define specific, meaningful events. We are exploring how brain systems encode information in the form of memories and also how memories are expressed and used to modify information processing at the time of retrieval. For example, a series of recent studies has identified a hippocampal-parietal pathway that contributes, in some manner, to the perception that information is old. This pathway participates in remembering and is dysfunctional in Alzheimer’s disease. We are presently using fMRI, MEG/EEG, and monkey physiology to better understand the specific processing contributions this memory pathway makes to information processing.
How does the brain represent the content of information in memory? We all know from our daily experiences that we can remember sounds and visual images from the past. However, it is largely a mystery how the human brain revives and represents these perceptions. We are exploring this issue in its most basic form by testing hypotheses such as whether human visual cortex becomes active when we try to retrieve a visually-based memory and whether auditory cortex becomes active when a sound from the past in remembered. An interesting area of emerging inquiry is how we use such perceptions prospectively to build anticipations of the future and mental simulations of what might happen next.
How does spontaneous activity contribute to information processing? A recent, remarkable observation is that a great deal of structured brain activity persists at rest, independent of immediate task goals. We are actively exploring whether spontaneous structured activity events contribute to consolidation of recent experiences and/or mental simulation of past and future events. One function of spontaneous activity, which persists during sleep and unconscious states, may be to replay recent activity patterns to consolidate them into brain networks. Another function might be to consider future possibilities — through guided mind wandering — to use downtime to explore possible future events before they happen.
Why do individuals differ in their memory and cognitive abilities? Advances in imaging technology and emerging genomic information make possible the mechanistic understanding of why abilities and cognitive styles differ among people. We are exploring this issue by studying individual differences at functional-anatomic levels of analysis in relation to performance differences. Our longer-term goal is to launch a large-scale study of several thousand individuals to provide an open-access data library that can be mined to understand functional-anatomic differences in relation to genetic variation.
How are memory systems used adaptively in the context of decisions, planning, and social interactions? Traditionally, with some notable exceptions, remembering the past has been studied without consideration of its adaptive value to cognition. We have recently begun to explore how memory systems provide constraints to aid decisions in a range of contexts including thinking about the future (prospection), conceiving the perspective of others, and navigation. To aid this research we are building virtual reality environments to systematically manipulate a subject’s opportunities to draw on past experience and to predict upcoming situations.
Our general approach is to explore these questions behaviorally and then apply a number of techniques to probe the functional-anatomic basis including fMRI, MEG, studies of patients with implanted intracranial electrodes, and studies with non-human primates. We are also interested in how information about the healthy brain can help to guide our understanding of damaged and diseased brain states such as occur after when a tumor has formed or during the progression of Alzheimer's Disease.
A final focus of our laboratory is to develop novel methods for functional neuroimaging that can be applied to questions about memory and cognitive neuroscientific questions more generally. For example, we pioneered and refined methods for extracting fMRI correlates of isolated mental events (called event-related fMRI or ER-fMRI methods). These methods allow us to sort memory events based on subject performance such as whether a specific item is remembered or forgotten, and to randomly present new or repeated items to subjects and separate the neural signals associated with each kind of event. Recently, we have focused on developing neuroinformatics and computational methods that allow integration and pooling of data across multiple modalities.