2014 Theses Doctoral

Brain mechanisms of affect and learning

Reinen, Jenna Marie

Learning and affect are considered empirically separable, but these constructs bidirectionally interact. While it has been demonstrated that dopamine supports the informational component of reward learning, the term "reward" inherently infers that a subjective positive experience is necessary to drive appetitive behavior.
In this dissertation, I will first review the ways in which dopamine operates on the levels of physiology and systems neuroscience to support learning from both positive and negative outcomes, as well as how this framework may be employed to study mechanism and disease. I will then review the ways in which learning may interact with or be supported by other brain systems, starting with affective networks and extending into systems that support memory and other types of broader decision making processes. Finally, my introduction will discuss a disease model, schizophrenia, and how applying questions pertaining to learning theory may contribute to understanding symptom-related mechanisms.
The first study (Chapter 2) will address the way in which affective and sensory mechanisms may alter pain-related decisions. I will demonstrate that subjects will choose to experience a stimulus that incorporates a moment of pain relief over a shorter stimulus that encompasses less net pain, and will suggest that the positive prediction error associated with the pain relief may modulate explicit memory in such a way that impacts later decision making.
In the second study (Chapter 3), I will examine reward learning in patients with schizophrenia, and demonstrate selective learning deficits from gains as opposed to losses, as well as relationships in performance to affective and motivational symptoms. The third study (Chapter 4) will extend this disease model to a novel cohort of subjects who perform the same reward learning task while undergoing functional MRI. The data from this chapter will reveal deficits in the patient group during choice in orbitofrontal cortex, as well as an abnormal pattern of learning signal responses during feedback versus outcome, particularly in orbitofrontal cortex, a finding that correlates with affective symptoms in medial PFC.
Taken together, these data demonstrate that learning is comprised of both informational and affective processes that incorporate input from dopaminergic midbrain neurons and its targets, as well as integration from other affective, mnemonic, and sensory regions to support healthy learning, emotion, and adaptive behavior.