Periodic Reporting for period 3 - RewardedPerception (Functional circuits mediating the effects of reward value on perception within and across sensory modalities) Reporting period: 2020-02-01 to 2021-07-31 Summary of the context and overall objectives of the project Our lab is interested in the mechanisms by which reward value influences human behavior. Humans learn the rules of a new game by observing wins and losses associated with each option. They gather motivation to take up a challenging task, such a marathon race, by imagining the reward of passing the finish line. The decision to invest in one particular stock market is guided by weighing the profits gained compared to other investments. Given the importance of reward processing for our goal-directed decisions, the impairment of the underlying neural mechanisms can have drastic pathological consequences, as demonstrated in cases such as addiction, depression and even psychosis. Recently, it has been demonstrated that reward signals are not only represented in our brains in terms of their hedonic value or expected utility, but also have a strong effect on the very basic mechanisms of sensory processing. Stimuli associated with high reward have been consistently shown to have a richer and stronger sensory representation than those paired with low rewards. This sensory hyper-sensitization can explain certain pathological states such as enhanced responsiveness of addicted patients towards hedonic cues. On the other hand, when used under controlled conditions, the sensory hyper-sensitization can be used in clinical settings to rehabilitate perceptual impairments such as poor vision or audition. RewardedPerception Project tries to unravel the basic neural mechanisms through which reward value influences sensory processing. To this end, we use a combination of behavioral testing, neuroimaging (electroencephalography; EEG, functional magnetic resonance imaging; fMRI) and advanced data analysis methods. This approach allows us to characterize sensory functions, which can be modulated by associated reward value of different stimuli and the functional circuits that underlie these behavioral effects. Specifically, reward effects on sensory perception require a close communication between brain areas that encode the associated value of a stimulus with areas that track its sensory features. Revealing how this communication is implemented in the brain, and ultimately devising methods to alter it when clinical intervention is warranted, is the ultimate goal of our research. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far We have so far, characterized several behavioral effects of reward value on basic sensory functions. We have demonstrated that the associated value of stimuli from different sensory modalities (such as vision and audition) affects pupil responses, modulates the speed and trajectory of eye movements, and influences speed and accuracy of perceptual decisions. These effects are reflected in the earliest components of brain's electrical activity and show dependence on the sensory modality of the reward cues. With the use of functional Magnetic Resonance Imaging (fMRI), we seek to map the early sensory areas that underlie these behavioral and electrophysiological effects. Moreover, we try to shed light on the putative pathways that mediate the communication between high-level, value encoding brain areas and early sensory regions. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) Success of our approach will not only advance understanding of the basic neuronal processes that underlie reward effects but will also provide a significant progress towards using reward-based behavioral techniques and brain stimulation methodologies in clinical settings. These techniques can be employed to boost remaining brain functions after a lesion, in order to regain lost sensory functions on the one hand, and to counteract pathological brain states such as addiction and depression on the other hand.
