Humans routinely make complex decisions between alternative courses of action. Understanding how our brains enable us to do this is a fundamental question in neuroscience. A central hypothesis is that the brain represents the motivational relevance of the choice options through value signals. However, the neural code for value has remained elusive, and how the brain computes such values for multidimensional options remains unknown. This lack of knowledge has significant implications for society. It hinders our ability to adequately treat neuropsychiatric goal-directed disorders that affect millions worldwide and hampers the growing artificial-intelligence industry, which aims to develop agents capable of autonomous value-based decisions. This interdisciplinary project aims to take an important step towards deciphering the neural code for value through the combined use of cognitive neuroscience, computational modelling, and behavioral psychophysics methods. Specifically, the main objectives were:
Objective 1: Deciphering the neural code for value. We know very little about how value signals are coded by neurons. Single-unit recordings in the orbital frontal cortex (OFC) of non-human primates – an analogue of the human ventromedial prefrontal cortex (vmPFC) – have identified neurons that encode the subjective value of options in a linear manner, either increasing or decreasing their activity with value. However, non-linear population codes, where each neuron is tuned to a specific stimulus magnitude, could allow neuronal ensembles to represent both value magnitude and uncertainty simultaneously. Our aim was to investigate whether the human brain utilizes such a probabilistic neural code for value.
Objective 2: Establishing how the neural code for value shapes behavior. If the human brain employs a probabilistic code for value, representing both value and value uncertainty within the same neuronal populations, the properties of these value signals could explain why individuals vary in their preferences, make inconsistent choices, and how they form confidence judgments. Our aim was to establish a link between the neural code for value and how neural uncertainty about value shapes behavior.
Objective 3: Establishing how value is constructed from our senses. Rewards often consist of multiple dimensions, such as an apartment’s size, location, brightness, and price. How the brain integrates these attributes, inferred from our senses, into a global value remains elusive. Our aim was to investigate whether the brain calculates this global value by weighting the different attributes of a reward based on the precision of their perceptual representation.
