Valuation and decision-making in frontal cortex: one or many serial or parallel systems?

Trial-type dependent frames of reference for value comparison

A central question in cognitive neuroscience regards the means by which options are compared and decisions are resolved during value-guided choice. It is clear that several component processes are needed; these include identifying options, a value-based comparison, and implementation of actions to execute the decision. What is less clear is the temporal precedence and functional organisation of these component processes in the brain. Competing models of decision making have proposed that value comparison may occur in the space of alternative actions, or in the space of abstract goods. We hypothesized that the signals observed might in fact depend upon the framing of the decision. We recorded magnetoencephalographic data from humans performing value-guided choices in which two closely related trial types were interleaved. In the first trial type, each option was revealed separately, potentially causing subjects to estimate each action's value as it was revealed and perform comparison in action-space. In the second trial type, both options were presented simultaneously, potentially leading to comparison in abstract goods-space prior to commitment to a specific action. Distinct activity patterns (in distinct brain regions) on the two trial types demonstrated that the observed frame of reference used for decision making indeed differed, despite the information presented being formally identical, between the two trial types. This provides a potential reconciliation of conflicting accounts of value-guided choice.

There are several competing theories of how the primate brain supports the ability to choose between different opportunities to obtain rewards – such as food, shelter, or more abstract goods (e.g. money). These theories suggest that the comparison of different options is either fundamentally dependent upon regions in prefrontal cortex (in which representations of abstract goods are often found), or upon motoric areas such as pre-motor and motor cortices (in which representations of specific actions are found). Evidence has been provided in support of both theories, derived largely from studies using different behavioural tasks. In this study, we show that a subtle manipulation in the behavioural task can have profound consequences for which brain regions appear to support value comparison. We recorded whole-brain magnetoencephalography data whilst subjects performed a decision task. Value comparison-related 13–30 Hz oscillations were found in ‘goods space’ in ventromedial prefrontal cortex in one trial type, but in ‘action space’ in pre-motor and primary motor cortices in another trial type - despite information presented being identical across trial types. This suggests both decision mechanisms are available in the brain, and that the brain adopts the most appropriate mechanism depending upon the current context.

What makes Internet addicts continue playing online even when faced by severe negative consequences? Possible explanations from an fMRI study

In this study, we designed a continuous wins-and-losses task to monitor the mental activities during decision-making and their effects on subsequent decisions in Internet addiction disorder (IAD) subjects. In behavioral performance, IAD subjects show longer response time, lower repeat rate and greater Stroop effect than healthy controls. In neuroimaging results, IAD subjects show increased brain activities in the inferior frontal cortex, insula, anterior cingulate cortex and decreased activation in the caudate and posterior cingulate cortex after continuous wins than healthy controls. In addition, IAD subjects show increased brain activities in the inferior frontal gyrus and decreased brain activation in the posterior cingulate cortex after continuous losses. Thus, we concluded that IAD subjects engage more cognitive activities to finish the decision-making task. As a result, they cannot sufficiently focus on the executive function during this process. They also do not pay adequate attention to considering previous selections and relevant outcomes during decision-making.

Beta coherence within human ventromedial prefrontal cortex precedes affective value choices

Ventromedial prefrontal cortex (vmPFC) forms a core region of larger brain circuits that assign value to sensory inputs and interfaces motivational and cognitive dominated brain processes. This network function of the vmPFC could be realized by synchronizing local activity at time scales that are shared by connected brain areas, but it is unknown whether vmPFC circuitry engages in functionally specific synchronization. Here, we recorded in human subcallosal vmPFC while subjects engaged in an emotion tracking task that required the assignment of positive or negative affective value to ambiguous (happy-sad) facial expressions. We found that vmPFC engages in low beta-band (15-20 Hz) coherent activation just before subjects subjectively judged ambiguous facial expressions as conveying negative valence ('sad') information, but not before positive valence ('happy') judgments. The predictive beta coherence emerged particularly for conflicting rather than pure emotional facial cues and dissipated slowly after the choice was made. These results suggest that 15-20 Hz coherent activity within vmPFC marks a functional signature of a valuation process that informs categorical affective choices. We hypothesize that coherent beta band activation signifies functional interactions to anatomical vmPFC projection targets, raising the possibility that dysfunctional biases in affective valuation and an enhanced decision conflict in clinical depression could be indexed by alterations of beta coherent network activation.

The location of feedback-related activity in the midcingulate cortex is predicted by local morphology

Information processing in the medial frontal cortex is often said to be modulated in pathological conditions or by individual traits. This has been observed in neuroimaging and event-related potential studies centered in particular on midcingulate cortex (MCC) functions. This region of the brain is characterized by considerable intersubject morphological variability. Whereas in a subset of hemispheres only a single cingulate sulcus (cgs) is present, a majority of hemispheres exhibit an additional sulcus referred to as the paracingulate sulcus (pcgs). The present functional magnetic resonance imaging study defined the relationship between the local morphology of the cingulate/paracingulate sulcal complex and feedback-related activity. Human subjects performed a trial-and-error learning task in which they had to discover which one of a set of abstract stimuli was the best option. Feedback was provided by means of fruit juice, as in studies with monkeys. A subject-by-subject analysis revealed that the feedback-related activity during exploration was systematically located in the cgs when no pcgs was observed, but in the pcgs when the latter sulcus was present. The activations had the same functional signature when located in either the cgs or in the pcgs, confirming that both regions were homologues. Together, the results show that the location of feedback-related MCC activity can be predicted from morphological features of the cingulate/paracingulate complex.

Learning to represent reward structure: a key to adapting to complex environments

Predicting outcomes is a critical ability of humans and animals. The dopamine reward prediction error hypothesis, the driving force behind the recent progress in neural "value-based" decision making, states that dopamine activity encodes the signals for learning in order to predict a reward, that is, the difference between the actual and predicted reward, called the reward prediction error. However, this hypothesis and its underlying assumptions limit the prediction and its error as reactively triggered by momentary environmental events. Reviewing the assumptions and some of the latest findings, we suggest that the internal state representation is learned to reflect the environmental reward structure, and we propose a new hypothesis - the dopamine reward structural learning hypothesis - in which dopamine activity encodes multiplex signals for learning in order to represent reward structure in the internal state, leading to better reward prediction.

How expert advice influences decision making

People often use expert advice when making decisions in our society, but how we are influenced by this advice has yet to be understood. To address this, using functional magnetic resonance imaging, we provided expert and novice advice to participants during an estimation task. Participants reported that they valued expert advice more than novice advice, and activity in the ventral striatum correlated with this valuation, even before decisions with the advice were made. When using advice, participants compared their initial opinion to their advisor’s opinion. This comparison, termed the “opinion difference”, influenced advice utilization and was represented in reward-sensitive brain regions. Finally, the left lateral orbitofrontal cortex integrated both the size of the opinion difference and the advisor’s level of expertise, and average activity in this area correlated with mean advice utilization across participants. Taken together, these findings provide neural evidence for how advice engenders behavioral change during the decision-making process.