Neuropsychological and Morphometric Correlates of Decision Making with the Coin Flip Task
The purpose of this study was to determine how older adults perform on a decisionmaking task (referred to as the Coin Flip Task) and how this performance correlates with demographic, neuropsychological, and brain morphometry variables. The study of decision making ability among older adults is important for several reasons. First, older adults frequently make "weighty" decisions as they age, such as important financial and medical decisions. When less than optimal decisions are made, it is difficult for the older adult to recover from or fix that decision given their relatively limited longevity. Second, decision making ability emanates from a brain area (the prefrontal cortex) that is known to undergo the greatest age related decline in normal aging, making sound decision making that much more crucial. From a biomedical perspective, understanding the mechanisms of how people age can help medical personnel to better tailor medicine and engineer devices that can assist the elderly in their lives and assure that they are well cared for. In the current study, 55 community dwelling, healthy older adult participants visited our laboratory for a series of visits that assessed their cognitive health, measured their decision making abilities, and measured their brain's structure and functioning. First, participants' Coin Flip performance was analyzed. We did this a number of ways. One approach was to subdivide our sample into three clusters that varied based on their Coin Flip behavior (i.e. H T NG poor decision makers; H T= mildly advantageous decision makers; H/T= advantageous decision makers) Next, we looked at associations between participants' coin flip performance and their demographic and neuropsychological data. Several relationships between Coin Flip performance and the neuropsychological variables were identified, including findings involving both cognition Correlates of Decision Making with the Coin Flip Task 3 and psychological/personality variables. On the cognitive side, more advantageous Coin Flip performances was positively associated with psychomotor speed, executive functioning, and interoceptive sensitivity, to name just a few. On the psychological/personality side, more advantageous Coin Flip performances was negatively associated with self reported anxiety. Finally, we correlated Coin Flip performance with cortical thickness. That analysis revealed several significant findings. One particularly robust finding indicated that older adults with more advantageous Coin Flip Task performance displayed greater cortical thickness an area of the prefrontal cortex, called the superior frontal region. The results are discussed in the context of the literature on the cognitive neuroscience of aging. Study limitations and future directions are also addressed. Correlates of Decision Making with the Coin Flip Task 4 Studying decision making in today's world serves many advantages. Understanding the affects ageing has on decision making can help family and medical professionals better treat and care for the again population. In this study, we utilized a decision making task called Coin Flip in older adults to measure their ability to make good or poor decisions. These same older adults also completed a neuropsychological examination as well as an sMRI scan to measure the thickness of the grey matter surrounding their pre frontal cortex. The purpose behind this was to understand how agerelated defects in the pre frontal cortex affect decision making in the older adult population. This study also observes how different emotional and behavioral variables in this population affected their performance on the decision making task. Studying Decision Making (DM) in the Laboratory When one makes decisions, there are two types of conditions that their decisions may fall under: risk or ambiguity. The difference in the two lies in a person's ability to know the probability of their choice, as well as the reward value associated with one's decision. In decisions involving risk, a person is aware of their probability of choosing the correct answer, whereas in decisions involving ambiguity, a person does not know the probability or believes that the probability is close to chance. Also, in decisions involving risk there is a known value associated with each decision, whereas in decisions involving ambiguity there is no difference in the reward value of each decision (Krain et al, 2006) This study focused on the use of the Coin Flip task, a measure that asks participants to make decisions under risk. There is a known probability for each decision made, and there is an assigned reward value for each decision made. Decisions made under risk Correlates of Decision Making with the Coin Flip Task 5 utilize an area of the brain called the prefrontal cortex, and more specifically, the orbitofrontal and medial frontal cortices (Krain et al, 2006) How the Brain Changes with Age As people age, there are distinct changes that occur in the anatomy (both gross and microscopically) of the brain that researchers can observe in order to understand its effect on human behavior and cognition. The Frontal Lobe Hypothesis of Aging suggests that the prefrontal cortex (PFC) is at a higher risk of deterioration, than other brain areas, in regard to normal aging and can lead to impaired functioning in older adults (West, 1999) Let it be noted that the PFC (located in the frontal lobe posterior to the motor strip) is where a large portion of a human's decision making, planning, and personality lie. The hypothesis supports that a decline in cognition associated with the PFC can be observed earlier and in greater magnitude than cognition associated with non frontal regions (West, 1999) A concept that has been argued in opposition to the the Frontal Lobe Hypothesis of Aging is that when an area within the frontal region decreases its function, another area in the frontal region increases its function (Cabeza et al. 1997, Grady 1998) Therefore, we can assume that age related declines and changes in the human brain are not universal, nor uniform across regions. It is for this reason that when we observe the PFC in regard to this study, it will be within specific regions of interest. How Emotion Impacts Decision Making The Somatic Marker Hypothesis states that decision making is a complex process that is assisted by emotional processes and somatic markers, which can occur through both the body, peripheral nervous system, and brain regions such as the VMPC and amygdala to name a few (Denburg et al. 2007) This hypothesis is supported through Correlates of Decision Making with the Coin Flip Task 6 studies such as Bechara's use of the Iowa Gambling Task (IGT) The Iowa Gambling Task is a measure that utilizes four decks of cards and gives the participant rewards and punishments based on decisions they make throughout the task. The goal of the Iowa Gambling Task is for the user to win as much money as they can. The participant must go through a series of 100 selections from one of the four decks labeled A, B, C, and D and is not notified on how many selections they must make before the task is over. Each deck is stacked with cards that either wins the user money or takes the user's money away. Stacks A and B are stacked with cards that win the user a high amount of money quickly, but also take away a great deal of money quickly. Stacks C and D contain cards that steadily win the user money, even as it takes small gains away. Historically, normal users follow a trend in which they begin the task picking from the A and B decks, but as the task progresses users begin to pick primarily from the C and D decks (Bechara et al. 2000) In one of his studies, Bechara wanted to see the effects that patients with a ventromedial prefrontal cortex lesion had on. The VMPCPC patients, when given the chance to perform the IGT, performed in a manner that suggested they were not learning appropriately as they selected cards; in other words, their decisions were not becoming more advantageous as the task progressed. The VMPC patients rather than selecting from the advantageous decks (C and D) towards the end of the task, continued to select from the disadvantageous decks (A and B) This showed that patients impaired in an emotional region within the PFC, were making poorer decisions as compared to their healthy counterparts (Bechara et al. 2000) Ways to Determine Neurological Health Correlates of Decision Making with the Coin Flip Task 7 In order to determine the neurological health of a person, a series of tests can be administered, and the resulting scores can be compared to normative data for a given age group. For this experiment, the following neuropsychological battery was administered: MMSE (Minnie Mental State Examination) a general Health Interview, Rey AuditoryVerbal Learning Test, Rey Complex Figure Test Wechsler Adult Intelligence Scale Digit Span and Coding, Judgement of Line Orientation test, Wechsler Abbreviated Scale of Intelligence, Beck Depression Index, and the Positive and Negative Affect Scedule) Before participants within our experiment were brought in to test, the following was asked of them to screen for any potential cognitive dysfunction that could exclude them from the study: "I will read you a list of health conditions, some of which are physical, and others are emotional conditions. To protect your privacy, please indicate at the end of the list with a yes or no that you have had any of the conditions without indicating specific ones. Please let me know if you have any questions about these conditions. Type I Diabetes; heavy drug or alcohol use; history of stroke; history of brain tumor; severe depression or anxiety necessitating inpatient psychiatric treatment; or a traumatic brain injury that resulted in a loss of consciousness that exceeded 10 minutes?" Once the participants were brought in for the initial neuropsychological screeni