Our research is focused on the intersection between learning, memory and decision making. How are decisions shaped by past experience? When are decisions guided by explicit knowledge, and when by implicitly learned associations or biases? Are explicit and implicit memories supported by independent cognitive and neural systems (as popular view suggests)? Or, is there some form of cross-talk between them? If so, do the underlying systems cooperate or compete?

To answer these questions, we adopt an integrative approach that draws broadly on neuroscience to make predictions about cognition. Predictions are tested in behavioral and neuroimaging studies in healthy individuals, and in patients with isolated damage to specific brain systems. Neuroimaging studies tell us about the spatial and temporal characteristics of neural mechanisms involved in cognition. Neuropsychological studies augment this approach and provide direct evidence of the necessity of a brain region for specific cognitive processes. Converging evidence from these complementary approaches produces a fuller picture of the cognitive and neural processes involved, and necessary, for different aspects of behavior.

Learning to predict uncertain outcomes
One core aspect of our research program is to understand the basic cognitive and neural processes that underlie incremental, feedback-based learning. This type of learning has traditionally been defined as implicit or procedural, and is thought to depend on the basal ganglia and its dopaminergic afferents. In this line of research, we aim to understand how and when different neural systems contribute to learning to predict outcomes. We are currently examining how the involvement of these neural systems is modulated by the predictability of the outcomes, by the timing, and nature, of the feedback, and by the amount of expertise a learner has.

Multiple learning mechanisms in the brain: Interactions between the medial temporal lobe and the basal ganglia
The basal ganglia and dopamine are thought to support incremental, feedback-based learning. A distinct and independent explicit or declarative system is thought to uniquely support memory for facts and events, and to depend on the hippocampal region. However, patient and imaging studies demonstrate that both implicit and explicit learning strategies guide decision-making in many settings. Furthermore, rather than operating as distinct systems, there is evidence to suggest various forms of interaction, or cross-talk, between them. We aim to understand the nature of the relationship between these different learning systems. Using fMRI and patient studies, we are currently examining, at both the behavioral and functional neurobiological levels, the temporal dynamics of neural systems engaged in different forms of learning, as well as the interaction between them.

Dopamine modulation of learning and decision-making
Dopamine has been widely implicated in incremental, feedback-based learning. The neuronal mechanisms of dopamine allude to its putative role for specific psychological processes, linking the basal ganglia learning system directly to feedback and reward. Interestingly, dopamine also innervates the hippocampus, and may play an important role in modulating long-term explicit memories. We seek to understand the role of dopamine in modulation of learning and decision making. To that end, ongoing FMRI studies are currently examining the role of dopaminergic regions in distinct psychological processes engaged during learning, such as motivation, stimulus processing, decision making, feedback processing and subsequent memory for experienced events. Parallel studies in patients are contrasting the effects of different types of dopamine modulation with different types of learning tasks and reward structures.

Development of learning and decision-making mechanisms in the brain
We are beginning to explore differential developmental changes in implicit and explicit memory and decision making, and their neural substrates. Our patient studies examine the effects of aging on learning and decision-making. In this line of research, we are using behavioral and functional imaging studies to examine these questions in children, in collaboration with Natasha Kirkham. Additionally, we are in the planning stages for conducting parallel behavioral and fMRI studies of learning and decision making during the intriguing developmental stage of adolescence.