We are conducting research on the brain mechanisms underlying both extrinsic motivations driven by the desire to obtain money or objects, and intrinsic motivations driven by curiosity to resolve uncertainty. Our research approaches include (1) cognitive neuroscience studies using neuroimaging, (2) psychophysiological studies using eye-tracking, and (3) neuropsychological studies with patients with neurodegenerative diseases and brain tumors.
In (1) cognitive neuroscience studies using neuroimaging, we have examined the neural mechanisms underlying how monetary rewards and punishments affect episodic memory. Our research has demonstrated that memory is enhanced not only by monetary rewards but also by punishments, and that such memory enhancement involves interactions between reward/punishment-related regions (ventral tegmental area, striatum, and insula) and memory-related regions (hippocampus) (Shigemune et al., Cereb. Cortex, 2014; Fig. 1). We have also shown that rewards enhance memory more effectively when memory retrieval is adequately difficult, and that such reward-difficulty interactions involve a neural network consisting of the medial prefrontal cortex (motivation-related region), ventral tegmental area (reward-related region), and hippocampus (memory-related region) (Shigemune et al., Hum. Brain Mapp., 2017; Fig. 2). Currently, we are investigating the neural mechanisms underlying memory processes when acquiring multiple rewards simultaneously. This research suggests that ventromedial prefrontal cortex activity compensates for ventral tegmental area activity, enabling the simultaneous acquisition of multiple rewards (Shigemune et al., IBRO2023, 2023).
In (2) psychophysiological studies using eye-tracking, we have examined how gambling addiction tendency affects attention distribution and pupil responses during gambling tasks. These studies have revealed that problem gamblers focus their attention more on the center of stimuli presented during gambling tasks, while non-problem gamblers focus more on the periphery (Shigemune et al., Cogn. Neurodyn., 2025; Fig. 3). We have also shown that problem gamblers exhibit greater pupil dilation when receiving rewards or punishments (manuscript under review; Fig. 4). Furthermore, we are advancing research on the relationship between gambling addiction tendency and decision-making regarding everyday objects and curiosity (abstract submitted; manuscript under review). These studies are supported by the Japan Keirin Association (JKA) through KEIRIN RACE funds.
In (3) neuropsychological studies with patients, we have investigated the decline in intrinsic motivation associated with dopaminergic system dysfunction in Parkinson’s disease patients, as well as changes in time perception due to depression and tumor location in brain tumor patients. In studies with Parkinson’s disease patients, we found that while curiosity-driven behavior (preferential viewing of uncertain vs. certain pictures) is maintained, overall picture viewing is reduced compared to controls due to dopaminergic system dysfunction (Shigemune et al., Neurol. Sci., 2021; Fig. 5). We also revealed that aversion to losing options is reduced in Parkinson’s disease patients due to dopaminergic system dysfunction (Shigemune et al., Neuropsychologia, 2022; Fig. 6). In studies with brain tumor patients, we demonstrated that depressed brain tumor patients show reduced perspectives of past, present, and future, with a proportional increase in past perspective and decrease in future perspective (Shigemune et al., J. Affect. Disord. Rep., 2021).
By studying both extrinsic and intrinsic motivation across diverse populations using multiple methodologies, we aim to answer the fundamental question: What drives human behavior?
