Academic journal article Cognitive, Affective and Behavioral Neuroscience

Dissociable Effects of Basolateral Amygdala Lesions on Decision Making Biases in Rats When Loss or Gain Is Emphasized

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Dissociable Effects of Basolateral Amygdala Lesions on Decision Making Biases in Rats When Loss or Gain Is Emphasized

Article excerpt

Published online: 26 March 2014

© Psychonomic Society, Inc. 2014

Abstract Individuals switch from risk seeking to risk aversion when mathematically identical options are described in terms of loss versus gains, as exemplified in the reflection and framing effects. Determining the neurobiology underlying such cognitive biases could inform our understanding of decision making in health and disease. Although reports vary, data using human subjects have implicated the amygdala in such biases. Animal models enable more detailed investigation of neurobiological mechanisms. We therefore tested whether basolateral amygdala (BLA) lesions would affect risk preference for gains or losses in rats. Choices in both paradigms were always between options of equal expected value-a guaranteed outcome, or the 50:50 chance of double or nothing. In the loss-chasing task, most rats exhibited strong risk seeking preferences, gambling at the risk of incurring double the penalty, regardless of the size of the guaranteed loss. In the betting task, the majority of animals were equivocal in their choice, irrespective of bet size; however, a wager-sensitive subgroup progressively shifted away fromthe uncertain option as the bet size increased,which is reminiscent of risk aversion. BLA lesions increased preference for the smaller guaranteed loss in the loss-chasing task, without affecting choice on the betting task, which is indicative of reduced risk seeking for losses, but intact risk aversion for gains. These data support the hypothesis that the amygdala plays a more prominent role in choice biases related to losses. Given the importance of the amygdala in representing negative affect, the aversive emotional reaction to loss, rather than aberrant estimations of probability or loss magnitude, may underlie risk seeking for losses.

Keywords Reflection effect . Framing effect .Risk aversion . Prospect theory . Loss-chasing . Gambling

Human decision making under uncertainty is influenced by cognitive biases that can precipitate suboptimal choices in terms of profit maximization (Tversky & Kahneman, 1974). Such phenomena include the reflection and framing effects, whereby subjects reverse their risk preferences in mathematically equivalent decisions, from risk seeking when options concern losses to risk-averse when considering gains (Murphy et al., 2009; Shafir & Tversky, 1995). Such biases are thought to arise because the relationship between the subjective and actual value is convex for losses, yet concave for gains (Kahneman & Tversky, 1979). In pathological gambling, risk seeking for losses contributes to excessive gambling in order to recover money lost, or "loss-chasing" (Dickerson, Hinchy, & Fabre, 1987; Lesieur, 1979). Understanding the neurobiology underlying these biases could therefore advance our appreciation of both normal and impaired decision making.

Neuroimaging data have indicated a critical role for the amygdala, an area heavily implicated in affective processing, in calculating the expected value of loss-related, but not gainrelated, outcomes (Canessa et al., 2013; Yacubian et al., 2006). When choosing between outcome-equivalent certain or uncertain options, subjects preferred the guaranteed option in the gain frame but gambled more frequently to evade losses, and activity in the amygdala increased when subjects favored this strategy (De Martino, Kumaran, Seymour, & Dolan, 2006; Roiser et al., 2009). Decisions made when considering losses versus gains also generated a greater skin conductance response (De Martino, Harrison, Knafo, Bird, & Dolan, 2008), indicating that emotion-based evaluations drive these biases (De Martino et al., 2006; Kahneman & Frederick, 2007). Patients with highly localized amygdala damage also failed to show risk seeking for losses, although risk aversion for gains was unaffected (Canessa et al., 2013; De Martino, Camerer, &Adolphs, 2010). However, other data have indicated the opposite, with amygdala damage decreasing only risk aversion (Shiv,Loewenstein, Bechara, Damasio, & Damasio 2005;Weller, Levin, Shiv, & Bechara, 2007), and an intact framing effect has been observed in two patients with complete amygdala degeneration due to Urbach-Wiethe disease (Talmi, Hurlemann, Patin, & Dolan, 2010). …

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