Abstract
Real-world decisions about reward often involve a complex counterbalance of risk and value. Although the nucleus accumbens has been implicated in the underlying neural substrate, its criticality to human behaviour remains an open question, best addressed with interventional methodology that probes the behavioural consequences of focal neural modulation. Combining a psychometric index of risky decision-making with transient electrical modulation of the nucleus accumbens, here we reveal profound, highly dynamic alteration of the relation between probability of reward and choice during therapeutic deep brain stimulation in four patients with treatment-resistant psychiatric disease. Short-lived phasic electrical stimulation of the region of the nucleus accumbens dynamically altered risk behaviour, transiently shifting the psychometric function towards more risky decisions only for the duration of stimulation. A critical, on-line role of human nucleus accumbens in dynamic risk control is thereby established.
Highlights
A cardinal problem in the neuroscience of human behaviour is the nature of the mediating link between a potential reward and the action intended to secure it (Platt and Huettel, 2008; Rangel et al, 2008)
In the absence of stimulation, all patients exhibited a strong monotonic relation between choosing the risky option and the associated reward probability that rose from a low floor to a high ceiling, indicating good sensitivity to risk and little baseline bias for either option (Fig. 3, black curves)
Nucleus accumbens stimulation induced a marked change in the decision behaviour of each participant manifesting as a consistent dynamic shift towards greater risk-seeking during the ‘on’ blocks (Fig. 3, red curves)
Summary
A cardinal problem in the neuroscience of human behaviour is the nature of the mediating link between a potential reward and the action intended to secure it (Platt and Huettel, 2008; Rangel et al, 2008). Human structural and functional imaging data have implicated the nucleus accumbens, a subregion of the ventral striatum exhibiting patterns of neuroanatomical connectivity and task-related neural activity optimally suited to such a role (Schultz et al, 1997; Matthews et al, 2004; O’Doherty et al, 2004; Cauda et al, 2011; Dalley et al, 2011).
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