Converging evidence from human lesion, animal lesion, and human functional neuroimaging studies implicates overlapping neural circuitry in ventral prefrontal cortex in decision-making and reversal learning. The ascending 5-HT and dopamine neurotransmitter systems have a modulatory role in both processes. There is accumulating evidence that measures of decision-making and reversal learning may be useful as functional markers of ventral prefrontal cortex integrity in psychiatric and neurological disorders. Whilst existing measures of decision-making may have superior sensitivity, reversal learning may offer superior selectivity, particularly within prefrontal cortex. Effective decision-making on existing measures requires the ability to adapt behaviour on the basis of changes in emotional significance, and this may underlie the shared neural circuitry with reversal learning.
Following brain injury to the orbitofrontal and ventromedial prefrontal cortex (PFC), human patients display gross alterations in social and emotional behaviour with largely preserved perception, language, memory, and even executive function (Bechara, Tranel, & Damasio, 2000; Damasio, 1994; Malloy, Bihrle, Duffy, & Cimino, 1993; Rolls, 1999). Characterisation of this profile using cognitive testing has been the target of considerable research, not least because the behaviour of patients with ventral prefrontal lesions resembles aspects of symptomatology seen in psychiatric conditions including psychopathy (Lapierre, Braun, & Hodgins, 1995) and substance abuse (Bechara & Damasio, 2002). Two cognitive domains have received particular attention in recent years: decision-making and reversal learning. The development of several measures of decision-making has stemmed largely from observations by Damasio, Bechara and colleagues, that patients with ventromedial prefrontal cortex damage are impaired in their ability to make successful everyday decisions regarding employment, relationships, and personal finances. Specifically, it has been proposed that these patients are unable to use past experiences to guide their ongoing decision-making (‘myopia for the future’) (Bechara et al., 2000; Damasio, 1994). Recent interest in reversal learning, in contrast, has developed from pre-clinical research over more than three decades demonstrating that rodents and non-human primates with lesions to the orbitofrontal cortex are unable to adapt their responding following changes in stimulus–reward contingencies (Butter, 1969; Jones & Mishkin, 1972).
The purpose of this article is to review converging evidence for the involvement of ventral prefrontal cortex in decision-making and reversal learning, from (1) human lesion studies, (2) animal lesion studies, and (3) human functional neuroimaging studies. Evidence for the contribution of the ascending 5-HT and dopamine neurotransmitter systems to these domains will also be described. Recent cognitive research in a number of clinical groups has begun to investigate the sensitivity and selectivity of decision-making and reversal learning deficits as indices of ventral prefrontal dysfunction.
