Fundamental Contribution by the Basolateral Amygdala to Different Forms of Decision Making

Abstract

Impairments in decision making about risks and rewards have been observed in patients with amygdala damage. Similarly, lesions of the basolateral amygdala (BLA) in rodents disrupts cost/benefit decision making, reducing preference for larger rewards obtainable after a delay or considerable physical effort. We assessed the effects of inactivation of the BLA on risk-and effort-based decision making, using discounting tasks conducted in an operant chamber. Separate groups of rats were trained on either a risk-or effort-discounting task, consisting of four blocks of 10 free-choice trials. Selection of one lever always delivered a smaller reward (one or two pellets), whereas responding on the other delivered a larger, four pellet reward. For risk discounting, the probability of receiving the larger reward decreased across trial blocks (100 -12.5%), whereas on the effort task, the larger reward was delivered after a ratio of presses that increased across blocks (2-20). Infusions of GABA agonists baclofen/muscimol into the BLA disrupted risk discounting, inducing a risk-averse pattern of choice, and increased response latencies and trial omissions, most prominently during trial blocks that provided the greatest uncertainty about the most beneficial course of action. Similar inactivations also increased effort discounting, reducing the preference for larger yet more costly rewards, even when the relative delays to reward delivery were equalized across response options. These findings point to a fundamental role for the BLA in different forms of cost/benefit decision making, facilitating an organism's ability to overcome a variety of costs (work, uncertainty, delays) to promote actions that may yield larger rewards.

Dissociable Contributions of Anterior Cingulate Cortex and Basolateral Amygdala on a Rodent Cost/Benefit Decision-Making Task of Cognitive Effort

“…Thus, it may be argued that this study's results and, notably, how they differ from previous studies, are due to unintended consequences of experimental design. However, the current methods closely adhered to a physical effort task with BLA inactivations (Ghods-Sharifi et al, 2009). Previous literature noted that loss of BLA function increased latency to choose (Ghods-Sharifi et al, 2009), whereas loss of ACC function increased motor impulsivity as measured by premature responding (Muir et al, 1996); critically, both effects were observed in this study.…”

“…As regards effort-based decision making, BLA inactivation decreases preference for high-effort options on both T-maze and operant lever-pressing (ie, physical) paradigms (Floresco and Ghods-Sharifi, 2007;Ghods-Sharifi et al, 2009). This leads to the prima facie assumption that BLA activity overpowers internal representations of cost in order to bias behavior toward highly rewarding options.…”

“…Surgery and microinfusion procedures were modeled after Floresco and Ghods-Sharifi (2007) and Ghods-Sharifi et al (2009). When baseline performance was deemed statistically stable (30-35 sessions), animals were implanted with 22-gauge stainless steel guide cannulae (Plastics One; Roanoke, VA, USA) bilaterally into the BLA or ACC using standard stereotaxic techniques.…”

Lesions of the Basolateral Amygdala and Orbitofrontal Cortex Differentially Affect Acquisition and Performance of a Rodent Gambling Task

“…This may be the first evidence of true risk-seeking behavior following amygdala damage that is independent of learning. These results are also unlikely to reflect an inability to adapt to changing task contingencies, such as those present in probability-discounting tasks (Ghods-Sharifi et al, 2009). It could be argued that this lesion-induced decline in rGT performance reflects a memory deficit, in that lesioned animals were unable to recall the correct strategy following surgery.…”

Pramipexole-Induced Increased Probabilistic Discounting: Comparison Between a Rodent Model of Parkinson's Disease and Controls

“…First, the ICSS-mediated discounting task was acquired by rats in the first test session, and stable baseline discounting was achieved in 3 days of testing. This contrasts food reinforcement discounting where typically 10 test sessions are needed for acquisition and 25-35 days are required to reach stable discounting behavior (St Onge et al, 2010;Ghods-Sharifi et al, 2009). Second, ICSS allows for testing several probabilities in a randomized order, a feature that is not successfully implemented with food-reinforced discounting (St Onge et al, 2010).…”