Tomada de decisão e a Tarefa de Jogo de Iowa
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개요
Fonte: Laboratórios de Jonas T. Kaplan e Sarah I. Gimbel – Universidade do Sul da Califórnia
A tomada de decisão é um componente importante da função executiva humana, na qual uma escolha sobre um curso de ação ou cognição é feita a partir de muitas possibilidades. Danos nas partes inferiores dos lóbulos frontais podem afetar a capacidade de uma pessoa tomar boas decisões. No entanto, embora os déficits decisórios possam ter um grande impacto na vida, esses déficits podem ser difíceis de quantificar em laboratório. Em meados da década de 1990, uma tarefa foi projetada para imitar a tomada de decisões da vida real em laboratório. Esta tarefa, conhecida como Iowa Gambling Task (IGT), é uma tarefa cognitivamente complexa amplamente usada em pesquisas e estudos clínicos como uma medida altamente sensível da capacidade de tomada de decisão. 1-3
No IGT, um participante é mostrado quatro baralhos de cartas e opta por revelar uma carta de um baralho em cada turno. Quando um cartão é entregue, o participante receberá algum dinheiro, mas às vezes também será obrigado a pagar uma multa. Dois dos decks têm maiores recompensas, mas também têm penalidades altas, de tal forma que escolher a partir desses decks leva a uma perda líquida a longo prazo. Os outros dois decks têm recompensas menores, mas também apresentam penalidades menores, de modo que a escolha desses decks leva a um ganho líquido. Assim, para fazer uma escolha vantajosa, os participantes devem integrar informações sobre perdas e ganhos ao longo do tempo.
Este vídeo demonstra como administrar o IGT para comparar o desempenho dos pacientes com danos ao córtex pré-frontal ventromedial a um grupo de sujeitos de controle combinados, revelando a contribuição única desta região cerebral para a tomada de decisões.
Procedure
Results
In 100-card draws from four decks, normal controls made more selections from the good decks (C and D), and avoided the bad decks (A and B). In contrast, patients with ventromedial prefrontal cortex (VMPFC) damage made more selections from the bad decks (A and B), and avoided the good decks (C and D; Figure 3). The number of cards selected by controls from decks A and B were significantly less than the number of cards selected from those decks by the patients. In contrast, the number of cards selected by the control population from decks C and D were significantly more than the number selected by patients.
Figure 3: Control subject and patient performance on the Iowa Gambling Task. In one hundred card selections from four decks, normal controls made more selections from the good decks (C and D), and were more apt to avoid the bad decks (A and B). In contrast, patients with ventromedial prefrontal cortex damage made more selections from the bad decks (A and B), and avoided choosing from the good decks (C and D).
These results show that the patients perform differently in this task from healthy controls, in that they tend to draw from high reward/high punishment decks more frequently even though these decks result in long term losses. Examination of the pattern of responses shows that this deficit in performance is stable over time. While controls initially sample from the bad decks, they eventually learn to avoid them. Patients, on the other hand, continue to sample from the bad decks throughout the experiment. Since participants must rely on their ability to estimate which decks are risky and which are profitable over time, patients' performance mimics their real-life inability to made advantageous decisions. This task allows the detection of the impairment in these patients in a laboratory setting, and provides insight into the role of the VMPFC, which appears crucial for incorporating emotional knowledge about decision outcomes into behavior.
Applications and Summary
This task can serve to assess decision-making deficits in a variety of populations. For example, in addition to patients with damage to the VMPFC, patients with bilateral amygdala damage also show severe decision-making impairments that can be measured by the IGT. Additionally, disadvantageous decision-making characterizes various psychopathological conditions, including substance addiction, pathological gambling, schizophrenia, obsessive-compulsive disorder, anorexia nervosa, attention deficit/hyperactivity disorder, psychopathy, obesity, and many others.
One of the advantages of this task is its ability to distinguish among different cognitive contributions to the complex process of decision-making. For example, we can compare the performance of patients with VPMFC damage to patients with schizophrenia, both of whom show deficits on the task. The tendency of VPMFC patients to choose from the bad decks has been interpreted as a deficit in incorporating information about long-term future consequences into behavior; in these patients, choices are made only on the basis of potential short-term reward. Patients with schizophrenia also choose more frequently from the bad decks than normal controls. However, their distinctive pattern of choices, in which they tend to choose more often from the decks with low frequency, high magnitude losses (decks B and D), reveals a different underlying deficit.4 This pattern of choices suggests that schizophrenic patients are sensitive to the frequency of reward versus punishment, but fail to advantageously take into account the magnitude of the punishment. Thus, the IGT is able to reveal a range of cognitive contributions to decision-making that may be associated with dysfunction in different brain regions.
References
- Bechara, A., Damasio, A.R., Damasio, H. & Anderson, S.W. Insensitivity to future consequences following damage to human prefrontal cortex. Cognition 50, 7-15 (1994).
- Bechara, A., Damasio, H., Tranel, D. & Damasio, A.R. Deciding advantageously before knowing the advantageous strategy. Science 275, 1293-1295 (1997).
- Li, X., Lu, Z.L., D'Argembeau, A., Ng, M. & Bechara, A. The Iowa Gambling Task in fMRI images. Hum Brain Mapp 31, 410-423 (2010).
- Shurman, B., Horan, W.P. & Nuechterlein, K.H. Schizophrenia patients demonstrate a distinctive pattern of decision-making impairment on the Iowa Gambling Task. Schizophr Res 72, 215-224 (2005).
내레이션 대본
Decision-making is an important component of human executive function, one in which a choice about a course of action is made from many possibilities.
For instance, a person’s ability to obtain a beverage could result from making good decisions, like choosing to go to the cash register and pay for it, or poor ones, such as running out the door without paying.
This latter example—the risky act of stealing—is considered an undesirable decision, one that occurs as a result of damage to the frontal lobes—and in particular, the ventromedial prefrontal cortex, VMPFC for short.
This video demonstrates how to design and execute the Iowa Gambling Task—a highly sensitive measure of complex decision-making ability—where individuals must integrate information about losses and gains over the course of a high-risk card game.
In this experiment, two groups of participants—patients with known damage to the VMPFC and controls, individuals without such damage—perform the Iowa Gambling Task, which examines decision-making ability dealing with reward and punishment.
All are shown four decks—labeled A through D—that contain identical-looking cards and given play money to use, as the overall goal is to maximize profit.
During each turn, participants choose one card from any of the four piles and subsequently receive a certain amount of predetermined money that only the researcher knows.
For instance, they might pick a card that results in not only winning money but also losing some. Or, they may even lose more than they win. The trick then is to understand the risk associated with every deck.
Although A and B yield greater rewards than C and D, they also result in higher penalties and thus, lead to losses in the long term. Decks A and B result in the same long term losses, but the punishment in A is more frequent and of lower magnitude than in B.
Overall, choosing from A and B will result in net losses, while choosing from C and D will result in net gains, which is why sets A and B are referred to as bad, and C and D as good.
Thus, to make advantageous choices, participants must integrate information about losses and gains over time and avoid the bad sets.
The dependent variable here is the number of card turns the participant makes from each of the four decks.
Based on previous work by Bechara, Damasio, and colleagues, patients with VMPFC damage are expected to make more selections from the bad ones—A and B—and avoid choosing from the good—C and D—mimicking their real-life inability to make valuable decisions.
For the purpose of this demonstration, test a patient with known cortical damage. Note that their data will be compared to those collected from controls without brain damage, who are also matched in age and intellect.
In preparation for the task, seat the patient at a table in front of four decks of identical-looking cards, and hand them $2000 in play money.
Instruct them that they must choose one card at a time from any of the four piles, and after flipping each card, they will receive a certain amount of money.
Further inform them that they are free to switch between decks at any time, as often as they want, and to take their time, in order to maximize their profit on the loan money.
Begin by having the patient make their first selection, and announce the amount of the reward or penalty according to the scorecard. Give them the amount of play money that they earn, and tell them to hand back any money they have lost before proceeding to the next turn.
Keep track of every card turn by marking the appropriate cell of the scorecard. In the event that a deck is completed before the experiment is over, notify the patient that they can now only choose from the three remaining decks. End the task when 100 cards have been turned.
To examine participants’ decisions over time, plot the deck selections across the course of the 100 trials—separately for controls versus patients with VMPFC damage.
While controls initially sampled from the bad decks, they eventually learned to avoid them. Patients, on the other hand, continued to sample from the bad ones throughout the experiment.
To make group comparisons, summarize these data into a bar graph, where the total number of card turns is plotted across decks.
Notice how normal controls made more selections from the good decks—C and D—and avoided the bad—A and B. On the other hand, patients with VMPFC damage made more selections from the bad sets, and largely avoided the good ones.
These results indicate that patients with frontal brain damage perform differently in this task compared to healthy controls, such that they more frequently draw from the high reward/high punishment decks, even though those decisions result in long-term losses.
Now that you are familiar with using the Iowa Gambling Task to quantify risky outcomes in patients with frontal lobe damage, let’s look at how the paradigm can be used to assess decision-making in a variety of populations, including individuals with amygdala damage and those diagnosed with schizophrenia.
While the role of the PFC in decision-making is well studied, other brain regions contribute to implementing advantageous versus disadvantageous choices.
Given the amygdala’s role in processing incentive stimuli, damage to this region would likely disrupt the integration of reward and punishment states vital to the gambling task.
Using a similar paradigm, researchers have shown that patients with bilateral amygdala damage also show severe decision-making impairments.
Just like patients with VMPFC damage, individuals with schizophrenia also choose from bad decks; however, they show a distinctive pattern of choices, making more selections from the low frequency but high magnitude losses—decks B and D.
These results indicate that schizophrenic patients are sensitive to reward versus punishment, but fail to advantageously take into account the magnitude of the punishment.
Thus, the Iowa Gambling task can be used to reveal a range of cognitive contributions to decision-making that may be associated with different underlying deficits.
You’ve just watched JoVE’s introduction to quantifying decision-making in the laboratory using the Iowa Gambling Task. Now you should have a good understanding of how to administer this paradigm by observing and responding to different card choices, as well as how to analyze and interpret the results.
Thanks for watching!