Twins Study Looks at Genetic Influences on Thinking
Feb. 16, 2010
A groundbreaking study by UT Dallas’ Center for Vital Longevity is focusing on twins in an effort to answer some long-debated questions about the rival influences of nature vs. nurture.
Researchers are seeking participants for the Texas Twins Study, which tests the genetic component of neurocognitive development among young adults. The study uses functional MRI technology to investigate brain activity among pairs of identical and fraternal twins.
“This study examines the evolutionary underpinnings of our brain, assessing which functions of our brain are programmed by our genes and which are more flexible and affected by environment. What we learn can have a major impact on approaches to education and how students might be helped by interventions.”
Dr. Denise Park, University Distinguished Chair in Behavioral and Brain Science
The study examines the pattern of neural activation in the human brain in response to various stimuli and tasks, as well as the differing roles played by nature – or genetics – and by nurture, which reflects how a person was raised and educated. The UT Dallas researchers use leading-edge technology to investigate a range of cognitive functions and their corresponding neuronal activity patterns.
By comparing twins, the researchers are able to learn more about the influence of genetics on our thinking and behavior by identifying differences in cognitive functions and neuronal activity. Identical twins share the same genetic pattern, while fraternal twins are no more alike than other siblings. To get a comparison between non-related individuals, scientists scramble the pairings and look at unrelated individuals from among the tested groups.
Neuroscientists have established that different categories of visual stimuli elicit distinct patterns of neural activity in the brain’s ventral visual cortex, which is associated with object recognition and form representation. Different parts of the brain are activated when people look at faces as opposed to when they view buildings and other outdoor scenes. Meanwhile, certain parts of the brain are engaged by words and letters, while other sections play a central role in processing symbolic or non-symbolic numerical information.
In a previous study with twins, the research team discovered the role of genetics in cortical response to various visual stimuli. Scientists determined that neural activity in the brains of identical twins is more similar than that of fraternal twins while performing the same simple task, indicating genes’ influence on recognizing faces and outdoor scenes.
“The activity was more similar in identical twins when they were looking at pictures of faces and places than when they looked at pictures of chairs, for example,” Park said. “Recognizing faces and locations is vitally important to survival, whereas identifying chairs is not, so we may be more genetically wired for tasks that are closely connected to survival.”
Researchers know less about the role that heredity might play in neural function as individuals engage in more complex tasks. The current study seeks to expand on the findings from the previous work.
Participants will perform two tasks as part of the project. The arithmetic section involves adding and subtracting sets of dots and judging whether the dots are similar geometric shapes. In the word task, participants will decide whether certain letter arrangements match or differ.
Park said she hopes the study reveals clues about how much our genes determine our math and reading abilities. Based on the previous findings, the answer may be connected to how essential these abilities are to our survival.
After the completion of this round of research, Park may embark on another twins study. She said she is interested in testing sets of elderly twins to find out how their neural activity is modified by aging. Park would like to know if genes play a smaller or larger role as we grow older.
Dr. Denise Park, director of the Center for Vital Longevity, says she hopes the study reveals clues about how much our genes determine math and reading ability.
Subjects Sought for Study
The Center for Vital Longevity is hoping to recruit more pairs of fraternal twins to fulfill its goal of testing and analyzing 15-20 pairs of monozygotic (identical) and 15-20 pairs of dizygotic (fraternal) twins, ages 18-30 years.
Though identical twins are rarer, recruitment of these participants has been easier. The study’s organizers have found that they tend to share the same interests and stay in closer contact than fraternal twins or other siblings, which enables participation in a study of this sort.
Fraternal twins who are interested in signing up for the study must be of the same gender. They initially will undergo screening for MRI safety and answer questions aimed at excluding potential participants who don’t meet the study’s criteria. To be included, individuals must be right-handed, fluent in English and have at least a 10th grade education.
After acceptance, the twins will fill out a brief online questionnaire about their physical similarities to their twins. Participation in the study involves a one-time visit to the Advanced Imaging Research Center at UT Southwestern Medical Center at Dallas. The twins will be taught how to perform certain tasks and then scanned with a functional MRI while performing those activities. The visit will last approximately two and a half hours, and participants will be paid $70 for their effort.