Neurocognitive processes in instrumental learning, response reversal, decision-making and psychopathy
This thesis investigates the neurocognitive systems involved in emotional processing, learning, and decision-making and considers the implications of dysfunction in these systems for psychopathy. The introductory chapter reviews the anatomy and function of the orbitofrontal cortex and amygdala and discusses why impairment in these regions may contribute to psychopathy. Chapter 2 introduces an investigation of the impact of emotional material on operant behaviour that showed that individuals with psychopathy do not display appropriate emotional modulation of attention. The subsequent three chapters investigate the performance of individuals with psychopathy on forms of instrumental learning that are dissociable at both the cognitive and neural levels. Chapter 3 investigates stimulus-reinforcement learning, a form of learning thought to rely on intact amygdala functioning, and found impaired performance in individuals with psychopathy. Chapter 4 presents findings of impaired reversal learning and decision making, which are indicative of orbitofrontal cortex dysfunction. Chapter 5 presents an investigation of conditional learning, which is a form of instrumental learning that is not dependent on the amygdala. As predicted by theories that emphasize amygdala and orbitofrontal cortex dysfunction in psychopathy, both groups performed similarly on the acquisition component of the conditional learning task, but individuals with psychopathy showed impairment on the second phase of the task when correct performance depended on reversing some of the acquired responses. Chapter 6 presents a case study that tests the analogy drawn between patients with lesions involving the orbitofrontal cortex and those with developmental psychopathy. The results show that the two disorders are characterized by sharply contrasting neurocognitive deficits. Chapter 7 reveals a functional Magnetic Resonance Imaging (fMRI) study addressing the basic question of whether discrete regions within the ventrolateral and orbitofrontal cortices are involved in signalling the need for response change and encoding the value of a reinforcer. The concluding chapter summarizes the results of the thesis and outlines future avenues of research that may arise from the work presented.