Periodic Reporting for period 4 - RewardedPerception (Functional circuits mediating the effects of reward value on perception within and across sensory modalities)
Période du rapport: 2021-08-01 au 2023-04-30
Our team is interested in understanding the mechanisms by which reward value influences human behaviour. 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 as a marathon race, by imagining the reward of crossing the finish line. The decision to invest in a 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.
The overarching objective of the RewardedPerception Project was to unravel the basic neural mechanisms through which reward value influences sensory processing. As such, this project provides a critical first step towards using reward-based effects in applied fields such neurodiagnostics or neurorehabilitation and educational settings.
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.
The overarching objective of the RewardedPerception Project was to unravel the basic neural mechanisms through which reward value influences sensory processing. As such, this project provides a critical first step towards using reward-based effects in applied fields such neurodiagnostics or neurorehabilitation and educational settings.
We hypothesised that reward-driven effects rely on a flexible communication of information between brain areas that encode reward value and those that track the sensory features of stimuli. To test this proposal, we used a combination of behavioural testing, neuroimaging (electroencephalography; EEG, functional magnetic resonance imaging; fMRI) and advanced data analysis methods. This approach allowed us to characterise the behavioural signatures of reward-driven effects under different contexts and to unravel their neuronal correlates in healthy human participants.
Two major findings of the project are depicted in the attached figure. In summary, we found that depending on the type of decisions that are made and on other contextual factors, such as the contingency of rewards on choices, different patterns of connections between brain areas underlie the reward-driven effects (see Figure 1). For instance, when a simple perceptual decision is underway (such as deciding on the tilt direction of the striped pattern in panel A) and rewards from visual or auditory modality are presented as task-irrelevant distractors, a network comprising higher valuations areas, attention- and sensory-related areas (OFC, IPS and V1/A1, respectively) orchestrate the reward-driven effects. In this case, coding of reward value in valuation areas is modality-independent (i.e. similar for visual and auditory rewards) but differentiates between the two later. However, in situations where a value-based decision between options is required (see panel B), especially when assigned values dynamically change, the differentiation of the source of rewards (visual versus auditory) occurs already at the level of higher valuation areas. This latter scheme allows a flexible adjustment of choice based on the changes in the surroundings.
Two major findings of the project are depicted in the attached figure. In summary, we found that depending on the type of decisions that are made and on other contextual factors, such as the contingency of rewards on choices, different patterns of connections between brain areas underlie the reward-driven effects (see Figure 1). For instance, when a simple perceptual decision is underway (such as deciding on the tilt direction of the striped pattern in panel A) and rewards from visual or auditory modality are presented as task-irrelevant distractors, a network comprising higher valuations areas, attention- and sensory-related areas (OFC, IPS and V1/A1, respectively) orchestrate the reward-driven effects. In this case, coding of reward value in valuation areas is modality-independent (i.e. similar for visual and auditory rewards) but differentiates between the two later. However, in situations where a value-based decision between options is required (see panel B), especially when assigned values dynamically change, the differentiation of the source of rewards (visual versus auditory) occurs already at the level of higher valuation areas. This latter scheme allows a flexible adjustment of choice based on the changes in the surroundings.
Revealing how reward-related information is communicated across the brain is the first step towards devising methods that can assist perceptual and value-based decisions when clinical intervention is needed. Therefore, our findings not only advance our understanding of the basic neuronal processes that underlie reward effects but also provide a significant progress towards using reward-based techniques, especially cross-modal rewards, in isolation or together with other methods such as brain stimulation methodologies in clinical settings. These techniques can be employed to exploit remaining brain functions after a lesion (for instance audition) in order to assist other functions that are impaired (for instance loss of vision in hemianopia). Additionally, the basic knowledge provided by our project can be used to counteract pathological brain states such as addiction and depression. Furthermore, understanding the motivational influences on decision-making can allow devising better learning tools in educational settings. These are important and exciting directions for future research in the field of basic and clinical neuroscience and educational psychology.