What is curiosity? How might the state of intending to learn differ from wanting to learn? We know that transitory states induced by thoughts or events -- for example, experimental manipulations of reward context -- affect the motivation to learn. Do relatively stable biological traits or psychological predispositions also figure in the dopamine-modulated enhancement of learning and memory?
Biological Trait Differences: Genetic characteristics
To study the role of dopamine in receptivity to learning and memory, we exploit individual variations in the dopamine availability in the brains due to common, naturally occuring genotype variations. Several polymorphisms that affect dopamine transport and catabolism have been found (e.g., DAT) and, using functional Magnetic Resonance imaging (fMRI), we aim to test the predictions that polymorphisms regulating this dopamine availability will affect anticipatory midbrain activations, and in turn, affect subsequent memory performance.
Psychological Trait Differences: Personality
We are also interested in understanding how individual differences in reward reactive disposition relate to midbrain neuromodulatory system activation during motivated learning and memory. For example, in previous studies from Sanghoon Han’s work with Ian Dobbins, regression analysis demonstrated that BAS (Behavioral Activation System) reward responsiveness personality scores significantly predicted ventral striatum (i.e., Nucleus Accumbens) activation during successful episodic recognition judgments. We are now investigating how stable personality traits such as reward seeking, novelty seeking, or impulsiveness mediate biological receptivity to learning.
Transitory State Differences
In addition to the investigation of these trait differences in neuromodulatory systems for learning and memory, we are exploring whether state differences induced by mood, stress, and by anti-psychotic pharmacological treatments affect reward-driven neuromodulation of learning.
Stable State Differences
The state-trait dichotomy often used to describe behavior leaves out one very interesting class of human behaviors: those that are relatively stable, like beliefs, habits, and chronic symptoms. With respect to this topic, we are testing whether anhedonia (the loss of interest and lack of reactivity to pleasurable stimuli) could be a potential state marker for dysfunction of the dopaminergic neuromodulatory system. We are also interested in whether the biology of motivated memory leads such states to be self-perpetuating.
By exploring all these factors, our approaches will elucidate how individual trait and state differences in dopaminergic neuromodulation system regulate memory formation and reward-based learning, thus providing insight into causes and potential treatments for a wide range of neurological and psychiatric disorders.
If you're interested in learning more, please contact Sanghoon Han (sh56_at_duke.edu)
state and trait
differences