Abstract
A paradigmatic example of an emotional bias in decision making is the framing effect, where the manner in which a choice is posed – as a potential loss or a potential gain – systematically biases an ensuing decision. Two fMRI studies have shown that the activation in the amygdala is modulated by the framing effect. Here, contrary to an expectation based on these studies, we show that two patients with Urbach-Wiethe (UW) disease, a rare condition associated with congenital, complete bilateral amygdala degeneration, exhibit an intact framing effect. However, choice preference in these patients did show a qualitatively distinct pattern compared to controls evident in an increased propensity to gamble, indicating that loss of amygdala function does exert an overall influence on risk-taking. These findings suggest either that amygdala does contribute to decision making but does not play a causal role in framing, or that UW is not a pure lesion model of amygdala function.
Highlights
Controls were risk-averse in the loss frame, t(19) = 2.66, p < .05, and did not differ significantly from riskneutrality in the win frame, t(19) = 1.86, p = 0.08
Patients gambled more frequently when the decision was framed as a potential loss than when it was framed as a potential gain
The influence of the frame was equivalent in patients and controls. This result is surprising because two fMRI studies (De Martino et al, 2006; Roiser et al, 2009) using the same task found that the interaction between frame and the decision to gamble modulated amygdala activation
Summary
In a paradigmatic experimental situation participants are asked to choose between a sure win or loss and a risky gamble. Such decisions should reflect maximisation of subjective utility, but it turns out these decisions are subject to subtle deviations from optimality that reflect the manner in which choices are framed. Brain imaging studies implicate the amygdala, orbitofrontal cortex (OFC) and the anterior cingulate cortex (ACC) in the framing effect (De Martino, Kumaran, Seymour, & Dolan, 2006; Roiser et al, 2009). Because ACC activation was greater when participants chose ‘against’ the frame (De Martino et al, 2006), it may modulate the motivational influence the amygdala exerts on choice. In humans the influence of Pavlovian cues on action vigour was associated with amygdala activation (Talmi, Seymour, Dayan, & Dolan, 2008), their influence on choice was not (Bray, Rangel, Shimojo, Balleine, & O’Doherty, 2008)
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