Neuronal recordings and lesion studies indicate that key aspects of economic decisions take place in the orbitofrontal cortex (OFC). Previous work identified in this area three groups of neurons ...encoding the offer value, the chosen value, and the identity of the chosen good. An important and open question is whether and how decisions could emerge from a neural circuit formed by these three populations. Here we adapted a biophysically realistic neural network previously proposed for perceptual decisions (Wang XJ. Neuron 36: 955-968, 2002; Wong KF, Wang XJ. J Neurosci 26: 1314-1328, 2006). The domain of economic decisions is significantly broader than that for which the model was originally designed, yet the model performed remarkably well. The input and output nodes of the network were naturally mapped onto two groups of cells in OFC. Surprisingly, the activity of interneurons in the network closely resembled that of the third group of cells, namely, chosen value cells. The model reproduced several phenomena related to the neuronal origins of choice variability. It also generated testable predictions on the excitatory/inhibitory nature of different neuronal populations and on their connectivity. Some aspects of the empirical data were not reproduced, but simple extensions of the model could overcome these limitations. These results render a biologically credible model for the neuronal mechanisms of economic decisions. They demonstrate that choices could emerge from the activity of cells in the OFC, suggesting that chosen value cells directly participate in the decision process. Importantly, Wang's model provides a platform to investigate the implications of neuroscience results for economic theory.
The orbitofrontal cortex plays a central role in good-based economic decisions. When subjects make choices, neurons in this region represent the identities and values of offered and chosen goods. ...Notably, choices in different behavioral contexts may involve a potentially infinite variety of goods. Thus a fundamental question concerns the stability versus flexibility of the decision circuit. Here we show in rhesus monkeys that neurons encoding the identity or the subjective value of particular goods in a given context 'remap' and become associated with different goods when the context changes. At the same time, the overall organization of the decision circuit and the function of individual cells remain stable across contexts. In particular, two neurons supporting the same decision in one context also support the same decision in different contexts. These results demonstrate how the same neural circuit can underlie economic decisions involving a large variety of goods.
Economic choices between goods are thought to rely on the orbitofrontal cortex (OFC), but the decision mechanisms remain poorly understood. To shed light on this fundamental issue, we recorded from ...the OFC of monkeys choosing between two juices offered sequentially. An analysis of firing rates across time windows revealed the presence of different groups of neurons similar to those previously identified under simultaneous offers. This observation suggested that economic decisions in the two modalities are formed in the same neural circuit. We then examined several hypotheses on the decision mechanisms. OFC neurons encoded good identities and values in a juice-based representation (labeled lines). Contrary to previous assessments, our data argued against the idea that decisions rely on mutual inhibition at the level of offer values. In fact, we showed that previous arguments for mutual inhibition were confounded by differences in value ranges. Instead, decisions seemed to involve mechanisms of circuit inhibition, whereby each offer value indirectly inhibited neurons encoding the opposite choice outcome. Our results reconcile a variety of previous findings and provide a general account for the neuronal underpinnings of economic choices.
•Economic choices under sequential offers are reflected in orbitofrontal cortex (OFC)•Neurons in OFC encode economic decision variables in a goods-based representation•Previous results suggesting that economic decisions rely on mutual inhibition were confounded•Economic decisions appear to rely on mechanisms of circuit inhibition
Ballesta and Padoa-Schioppa show that similar groups of neurons in the primate orbitofrontal cortex engage in choices between goods offered simultaneously or in sequence. Their results suggest that economic decisions rely on mechanisms of circuit inhibition whereby each offer value indirectly inhibits cells encoding the opposite choice outcome.
According to this second algorithm, subjects would first identify the attribute with highest variance and then choose according to that attribute alone (dimensional prioritization). Importantly, ...flavor is a subjective and complex sensation that cannot be reduced to the sum of simple components (Small, 2012; Spence, 2015). ...different flavors are effectively incommensurable commodities. The only way to compare apple flavor and orange flavor is to compute their subjective value, which is precisely what Piantadosi and Hayden argue against. ...algorithm 2 cannot account for choices as simple as that between an apple and an orange. In the integrated value framework, choices are made according to the utility function U = P R – C. This utility function cannot be decomposed into additive functions. ...the argument of Piantadosi and Hayden falls.
The primary motor cortex (M1) is known to control motor performance. Recent findings have also implicated M1 in motor learning, as neurons in this area show learning-related plasticity. In the ...present study, we analyzed the neuronal activity recorded in M1 in a force field adaptation task. Our goal was to investigate the neuronal reorganization across behavioral epochs (before, during, and after adaptation). Here we report two main findings. First, memory cells were present in two classes. With respect to the changes of preferred direction (Pd), these two classes complemented each other after readaptation. Second, for the entire neuronal population, the shift of Pd matched the shift observed for muscles. These results provide a framework whereby the activity of distinct neuronal subpopulations combines to subserve both functions of motor performance and motor learning.
In the eighteenth century, Daniel Bernoulli, Adam Smith and Jeremy Bentham proposed that economic choices rely on the computation and comparison of subjective values
. This hypothesis continues to ...inform modern economic theory
and research in behavioural economics
, but behavioural measures are ultimately not sufficient to verify the proposal
. Consistent with the hypothesis, when agents make choices, neurons in the orbitofrontal cortex (OFC) encode the subjective value of offered and chosen goods
. Value-encoding cells integrate multiple dimensions
, variability in the activity of each cell group correlates with variability in choices
and the population dynamics suggests the formation of a decision
. However, it is unclear whether these neural processes are causally related to choices. More generally, the evidence linking economic choices to value signals in the brain
remains correlational
. Here we show that neuronal activity in the OFC is causal to economic choices. We conducted two experiments using electrical stimulation in rhesus monkeys (Macaca mulatta). Low-current stimulation increased the subjective value of individual offers and thus predictably biased choices. Conversely, high-current stimulation disrupted both the computation and the comparison of subjective values, and thus increased choice variability. These results demonstrate a causal chain linking subjective values encoded in OFC to valuation and choice.
Adaptive Coding is the property of the brain to adjust its response to statistical properties of the environment. Its effect is an improved discrimination among signals under the constraints on the ...dynamic range of its response. It can thus be considered the neural correspondent of Rational Attention, which models how a rational decisionmaker allocates attention among different informative signals. There is strong evidence of existence of widespread adaptive coding. Adaptive coding introduces a dependence of choice from the environment which is not observed in behavior. We discuss potential solutions and propose Hebbian learning as a potentially satisfactory answer.
Economic choice is the behaviour observed when individuals select one among many available options. There is no intrinsically ‘correct’ answer: economic choice depends on subjective preferences. This ...behaviour is traditionally the object of economic analysis and is also of primary interest in psychology. However, the underlying mental processes and neuronal mechanisms are not well understood. Theories of human and animal choice have a cornerstone in the concept of ‘value’. Consider, for example, a monkey offered one raisin versus one piece of apple: behavioural evidence suggests that the animal chooses by assigning values to the two options. But where and how values are represented in the brain is unclear. Here we show that, during economic choice, neurons in the orbitofrontal cortex (OFC) encode the value of offered and chosen goods. Notably, OFC neurons encode value independently of visuospatial factors and motor responses. If a monkey chooses between A and B, neurons in the OFC encode the value of the two goods independently of whether A is presented on the right and B on the left, or vice versa. This trait distinguishes the OFC from other brain areas in which value modulates activity related to sensory or motor processes. Our results have broad implications for possible psychological models, suggesting that economic choice is essentially choice between goods rather than choice between actions. In this framework, neurons in the OFC seem to be a good candidate network for value assignment underlying economic choice.
A series of studies in which monkeys chose between two juices offered in variable amounts identified in the orbitofrontal cortex (OFC) different groups of neurons encoding the value of individual ...options (offer value), the binary choice outcome (chosen juice), and the chosen value. These variables capture both the input and the output of the choice process, suggesting that the cell groups identified in OFC constitute the building blocks of a decision circuit. Several lines of evidence support this hypothesis. However, in previous experiments offers were presented simultaneously, raising the question of whether current notions generalize to when goods are presented or are examined in sequence. Recently, Ballesta and Padoa-Schioppa (2019) examined OFC activity under sequential offers. An analysis of neuronal responses across time windows revealed that a small number of cell groups encoded specific sequences of variables. These sequences appeared analogous to the variables identified under simultaneous offers, but the correspondence remained tentative. Thus, in the present study, we examined the relation between cell groups found under sequential versus simultaneous offers. We recorded from the OFC while monkeys chose between different juices. Trials with simultaneous and sequential offers were randomly interleaved in each session. We classified cells in each choice modality, and we examined the relation between the two classifications. We found a strong correspondence; in other words, the cell groups measured under simultaneous offers and under sequential offers were one and the same. This result indicates that economic choices under simultaneous or sequential offers rely on the same neural circuit.
Research in the past 20 years has shed light on the neuronal underpinnings of economic choices. A large number of results indicates that decisions between goods are formed in a neural circuit within the orbitofrontal cortex. In most previous studies, subjects chose between two goods offered simultaneously. Yet, in daily situations, goods available for choice are often presented or examined in sequence. Here we recorded neuronal activity in the primate orbitofrontal cortex alternating trials under simultaneous and under sequential offers. Our analyses demonstrate that the same neural circuit supports choices in the two modalities. Hence, current notions on the neuronal mechanisms underlying economic decisions generalize to choices under sequential offers.
Values available for choice in different behavioral contexts can vary immensely. To compensate for this variability, neuronal circuits underlying economic decisions undergo adaptation. In ...orbitofrontal cortex (OFC), neurons encode the subjective value of offered and chosen goods in a quasilinear way. Previous experiments found that the gain of the encoding is lower when the value range is wider. However, the parameters OFC neurons adapted to remained unclear. Furthermore, previous studies did not examine additive changes in neuronal responses. Computational considerations indicate that these factors can directly impact choice behavior. Here we investigated how OFC neurons adapt to changes in the value range. We recorded from two male rhesus monkeys during a juice choice task. Each session was divided into two blocks of trials. In each block, juices were offered within a set range of values, and ranges changed between blocks. Across blocks, neuronal responses adapted to both the maximum and the minimum value, but only partially. As a result, the minimum neural activity was elevated in some value ranges relative to others. Through simulation of a linear decision model, we showed that increasing the minimum response increases choice variability, lowering the expected payoff. This effect is modulated by the balance between cells with positive and negative encoding. The presence of these two populations induces a non-monotonic relationship between the value range and choice efficacy, such that the expected payoff is highest for decisions in an intermediate value range.
Economic decisions are thought to rely on the orbitofrontal cortex (OFC). The values available for choice vary enormously in different contexts. Previous work showed that neurons in OFC encode values in a linear way, and that the gain of encoding is inversely related to the range of available values. However, the specific parameters driving adaptation remained unclear. Here we show that OFC neurons adapt to both the maximum and minimum value in the current context. However, adaptation is partial, leading to contextual changes in the response offset. Interestingly, increasing the activity offset negatively affects choices in a simulated network. Partial adaptation may allow the circuit to maintain information about context value at the cost of slightly reduced payoff.
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