Abstract
The Iowa Gambling Task (IGT) is a decision-making task that preferentially involves the right prefrontal cortex (PFC). However, the performance of the task is driven by two attributes: intertemporal (long vs. short-term) and frequency-based processing of rewards-punishments, and differs over the two phases of uncertainty (early trials) and risk (later trials). Although intertemporal decision making involves the right PFC, the extent of hemispheric specialization in attribute and phase-specific decision making is unknown. Therefore, the current study assessed decision making in a patient with a uni-hemispheric disease, who underwent hemispherotomy surgery, comparing pre-surgical IGT performance (3 days prior to surgery) with post-surgical performance (1 month, and 12 months post-surgery). The patient’s pre- and post-surgical IGT performances were analyzed to examine changes in attribute and phase-specific decision making, including the widely reported deck B phenomenon. The results for the two attributes of deck selection at the pre- and post-surgical assessments suggested marked changes in the two IGT phases of risk and uncertainty. Pre-surgery, the patient made more intertemporally disadvantageous choices, and task-progression contributed to it; within 1 month of surgery, intertemporal disadvantageous deck choices were contingent on task progression, after 1 year, disadvantageous choices were independent of task progression. Intertemporal attribute alteration was unresponsive to uncertainty and risk phase. The effect of task progression on frequency attribute remained unchanged before and immediately after the surgery, and preference for infrequent decks was observed only after 1 year. Further, pre and post surgery alteration in frequency attribute was phase-specific: within 1 month of surgery, infrequent deck choices decreased in uncertainty and increased in risk, whereas the reverse was observed after 12 months. Deck B choice increase was in the uncertainty phase. Results are discussed in reference to valence-linked hemispheric specialization and its potential role in attribute and phase-specific IGT decision making.
Highlights
The Iowa Gambling Task (IGT) was devised to account for decision making deficits in patients with focal damage in the ventromedial prefrontal cortex (PFC; Damasio, 1996)
We first examined IGT deck choices across the 100 trials of the task to determine whether choice of decks alters with task progression, separately for the two attributes assessed at three points
The implication of altered valence-processing linked with IGT decision making implies that the preference for the infrequent punishment deck B that is widely observed in females might be linked to valence-related lateralization, and potentially contributing to sex differences in attribute and phase-specificity in the IGT
Summary
The Iowa Gambling Task (IGT) was devised to account for decision making deficits in patients with focal damage in the ventromedial prefrontal cortex (PFC; Damasio, 1996). Even though the deficit in the IGT cannot be attributed to solely to epilepsy-linked structural or functional atrophy (Delazer et al, 2010), uni-hemispheric atrophy and post-surgery changes offer insights about the hemispheric contribution to cognitive functions, for instance, unihemispheric epilepsy localized either to the right or to the left hemisphere did not differ in terms of the deficit observed in the intertemporal IGT decision making (Bonatti et al, 2009; Labudda et al, 2009; Delazer et al, 2010, 2011). A rare case of female patient of Rasmussen Encephalitis epilepsy with left hemispheric atrophy is used for understanding how the two attributes (i.e., cognition-intensive and emotion-based attributes) in two phases differing in cognitive demands (i.e., uncertainty and risk) influence performance in a task that shows right-lateralitylinked male advantage. Analysis addressed pictures and words separately; and pictures at follow-up 2 used the ratings of set 1 (pictures shown prior to surgery) and of set 2 (pictures shown at post surgery follow up 1), in other words presurgery ratings (set 1), post surgery follow up 1 ratings (set 2), and post surgery follow up 2 ratings of set 1, and post surgery follow up 2 ratings of set 2 served as four levels of within-subject variable for analysis of valence processing
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