Gao, Melanie – University of Chicago

Gao, Melanie

Melanie Gao

Personal Section

Hundreds of years ago, human beings worked with their hands and often walked from

place to place. Nowadays, muscle power is no longer in high demand and cars have replaced

walking; concurrently, modern society has created cheaper food markets, increasingly more

restaurants, and a multi-million dollar fast food industry. Recent technology has decreased the

need for physical activity while increasing the availability of food. Though these modern

advances are a blessing, they have also brought harmful consequences for the human population.

These conveniences cause individuals to consume more calories than they use; in general,

people’s energy consumption is greater than their energy expenditure. This condition has lead to

a recent phenomenon—the obesity epidemic.

First noted in the United States in 1980, the obesity epidemic has since increased twofold

in recent decades. In the 21st century, obesity has become one of the leading health problems in

the United States; over 34% of all adults age 20 years and over and 18% of all children age 6-11

years are obese (CDC Faststats, Obesity and Overweight). In fact, obesity is more prevalent in

the United States than in other Westernized country. With obesity comes a vast array of health

concerns including hypertension, glaucoma, cardiovascular disease, type 2 diabetes, high blood

pressure, certain cancers and heart disease. According to the National Institutes of Health,

obesity is one of the leading cause of preventable death in the US, second only to tobacco usage;

obesity-related conditions cause approximately 300,000 deaths a year.

As a sophomore in high school, I did not know much about the obesity epidemic and I

vaguely understood the concept of eating healthy and exercising regularly. When I first entered

the basement of the Neurological Institute of New York, I did not plan on applying to the Intel

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Competition nor had I decided to obesity research. Rather, I joined the Columbia University

Medical Center’s Program for Imaging and Cognitive Sciences (PICS) at the end of sophomore

year because a strange fascination with the brain. I found it fascinating how a three-pound

pudding of cells and circuits control the thoughts and habits that make up who we are. I was

determined to learn more about the brain’s function and awaited the many discoveries and

surprises ahead with enthusiasm. I was infected with the research bug.

In the lab, I worked on various projects with other researchers in the lab, ranging from an

autism study to a study on auditory processes. Independently, I developed an interest in hunger

and satiety. At that time, a mentor recommended David Kessler’s book, The End of Overeating,

which revealed shocking statistics about obesity in America and attempted to explain why

humans are so attracted to food. I wanted to understand why individuals found food so

mouthwateringly attractive, and how the brain normally controls food intake; using the resources

provided at the fMRI lab, I hope to better understand and prevent obesity and save lives. David

Kessler’s book ultimately became the basis for my Intel project investigating how individuals

respond to healthy food and junk food, and the particular salience of junk food.

Despite a two-hour commute via boat, subway and bus to the lab on the Upper West Side

of Manhattan, I have interned at the lab for almost two years. I had to learn basic computer

science and statistics to use the main software at the lab, Presentation, and to analyze data. My

experience at the lab has challenged me to think scientifically, tuning myself to ask the right

questions. There are just so many questions one can ask that cannot be pursued, for reasons of

practicality or time or simply because technology has not advanced far enough. At the same

time, there are so many that have been answered in every field of neurology, small steps trekked

on the uncharted territory of the brain by hundreds of scientists.

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Through my experience at the lab, I have acquired a better understanding of the difficulty

of doing science; research is not as picture perfect as it appears in science journals. I have

changed my original project idea countless times and repeated the same experiment multiple

times. As a scientist, one must have patience and one must truly enjoy doing science. To me,

science is a hobby; I enjoy spending time playing around with computer programming, reading

science articles, running studies on subjects, analyzing countless data sets and finding the

connections that lie underneath beneath the numbers. Research offers me the chance to satisfy an

almost insatiable curiosity and a thirst for knowledge and I plan to continue the exploration of

science I began in high school. I aspire to impact the scientific world, one data set at a time.

Research Section

Abstract:

In western cultures, food images can be found everywhere in the environment—from

large restaurant ads to fast food restaurants located at many intersections. Despite the high

prevalence of obesity and eating disorders, the factors and systems that regulate human eating

behavior remain poorly understood. Understanding the relationship between control mechanisms

and food stimuli and the factors that affect this relationship may provide a better understanding

of the factors underlying obesity, and may reveal better methods for individuals seeking to

regulate their eating behaviors and maintain a healthy weight. This pilot study developed a

unique Stroop paradigm using biologically relevant food images (the “Food Stroop”) to

investigate the relationship between junk (high-calorie) food, compared with healthy (low-

calorie) food, and control mechanisms. To do so, this study evaluated the response times and

accuracies of individuals identifying junk and healthy food stimuli in a Stroop task. The analysis

was done comparing congruency conditions between each trial and the trial preceding it; analysis

of the effect of BMI, gender, age and education level on response times was completed to

determine the translational relevance and effect of various demographics. This study revealed

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that not only did junk food cues elicit a significantly faster response from individuals, but it also

prevented potential conflict and is sustained longer in the memory trace compared to healthy

food cues. Junk food is more potent than healthy food is and induces faster processing. This

implicates separate neural processing mechanisms for junk and healthy food and suggests that a

unique neural network may exist to specifically process junk food images at a significantly faster

speed.

1. Introduction:

1.1.

Recent Prevalence of Obesity

The recent rise in obesity and food-related disorders is a major source of concern and

expense in the US and other westernized countries. In April 2009, Dr. David Kessler, former US

Surgeon General, published a best-selling book “The End of Overeating”, in which he

documents the rise in obesity and food-related health concerns, and identifies the consumption of

junk-food as the primary cause. He states that most individuals, despite differences in weight,

age and ethnicity, find it difficult to resist junk food. Importantly, Kessler concludes that the

primary defense against succumbing to the health perils of junk food must come from the

individual’s education about junk food’s power to overcome their innate cognitive control

mechanisms, which control individuals’ ability to choose a healthy diet. Unfortunately, very

little is known about cognitive mechanisms for controlling one’s appetite, specifically in the

presence of junk food. In addition, there is little understanding on the difference in responses

induced by healthy or “low-calorie” food cues and junk or “high-calorie” food cues.

Accordingly, this study specifically investigates, for the first time, a measure of individuals’

cognitive control relative to junk-food images. Using a Stroop task, this study was able to

identify quantitatively, the power of junk food images to overcome conflict situations and induce

faster cognitive processing.

1.2.

The Stroop Task

Since its introduction in 1935 (Stroop, 1935), the Stroop task has been used to monitor

cognitive conflict and derive models of cognitive control. In a typical Stroop task, the natural

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processing of task-irrelevant stimuli (distracters) often

interferes with an

individual’s

performance on an identification task. In the classic Stroop task, participants are instructed to

identify the ink color of a color word in congruent and incongruent conditions. For example, in

the congruent condition, the stimuli consists of color words printed with the same color ink (i.e.,

the word RED printed in red ink), while in the incongruent condition, color words are printed in

a different ink color (i.e., the word RED printed in green ink). By comparing the response times

in these two conditions, an interference effect can be observed. The conflict in incongruent

conditions causes impaired cognitive performance; the “Stroop interference effect” is derived

from observations that participants are generally slower to identify ink colors in the incongruent

condition than in the congruent condition. These participants are distracted by the word because

reading is a more automatic process than color identification and thus, more difficult to inhibit

(Macleod & Macdonald, 2000). Interestingly, the interference, or “conflict”, produced by

incongruent task-irrelevant information in the incongruent condition is reduced if the

incongruent trial is preceded by another incongruent trial (incongruent-incongruent), compared

with when an incongruent trial is preceded by a congruent trial (congruent-incongruent) (Egner

and Hirsch 2005a; Notebaert et al. 2006). The superior performance on the second consecutive

task reveals an improved conflict resolution and suggests that the brain can rapidly adjust

processing mechanisms when exposed to consecutive conflict situations. This improved conflict

resolution mechanism helps overcome the conflict and induces better performance on the second

incongruent task. The “Conflict adaptation effect” describes the improved conflict resolution

following the presentation of two consecutive incongruent stimuli.

1.3 Food as a Biologically Relevant Stimuli

Food consumption is one of the most important human behaviors. Many factors influence

a person’s attraction to certain foods; certain physical characteristics of food, such as taste, smell

and appearance affect an individual’s attraction to food. Furthermore, through learning and

experience, the visual characteristics of food can act as reinforcers, capable of inducing eating-

related behavior (Lappalainen and Sjoden, 1992; Killgore et al., 2003). Food is salient because,

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