Making a left-hand turn requires a huge amount of brain activation and involves far more areas of the brain than driving on a straight road or other maneuvers

TORONTO, Feb. 28, 2013-- Most serious traffic accidents occur when drivers are making a left-hand turn at a busy intersection.

When those drivers are also talking on a hands-free cell phone, "that could be the most dangerous thing they ever do on the road," said Dr. Tom Schweizer, a researcher at St. Michael's Hospital.

Researchers led by Dr. Schweizer tested healthy young drivers operating a novel driving simulator equipped with a steering wheel, brake pedal and accelerator inside a high-powered functional MRI. All previous studies on distracted driving have used just a joy-stick or trackball or else patients passively watching scenarios on a screen.

Immersing a driving simulator with a fully functional steering wheel and pedals in an MRI at Sunnybrook Health Sciences Centre allowed researchers to map in real time which parts of the brain were activated or deactivated as the simulator took them through increasingly difficult driving maneuvers.

The researchers were able to show for the first time that making a left-hand turn requires a huge amount of brain activation and involves far more areas of the brain than driving on a straight road or other maneuvers.

When the drivers were also involved in a conversation, the part of the brain that controls vision significantly reduced its activity as the part that controls monitoring a conversation and attention was activated.

The research was published today online in the open access journal Frontiers in Human Neuroscience.

"Visually, a left-hand turn is quite demanding," Dr. Schweizer said. "You have to look at oncoming traffic, pedestrians and lights, and coordinate all that. Add talking on a cell phone, and your visual area shuts down significantly, which obviously is key to performing the maneuver."

The simulation had the drivers making six left turns with oncoming traffic, which required them to decide when to turn safely. It then distracted them, by making them answer a series of true-false audio questions, such as "Does a triangle have four sides?" The MRIs showed that blood moved from the visual cortex, which controls sight, to the prefrontal cortex, which controls decision-making.

"Brain activity shifted dramatically from the posterior, visual and spatial areas [of the brain] to the prefrontal cortex," said Dr. Schweizer, a neuroscientist and director of the Neuroscience Research Program at the hospital's Li Ka Shing Knowledge Institute.

"This study provides real-time neuroimaging evidence supporting previous behavioural observations suggesting that multitasking while driving may compromise vision and alertness. 'Hands free' not does mean 'brains free.'"

Dr. Schweizer said his study needed to be replicated in larger groups and with various age groups and with people with known brain impairments such as Alzheimer's disease.

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This study was funded by the Natural Sciences and Engineering Research Council of Canada and the Ontario Ministry of Economic Development and Innovation.

About St. Michael's Hospital

St. Michael's Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in more than 23 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, and care of the homeless are among the hospital's recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Center, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

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About Frontiers

Frontiers is a community-oriented open access scholarly publisher and social networking platform for researchers. Founded in 2007 by scientists in Switzerland, its industry leading platform together with a growing range of exciting and innovative open science tools, empowers all academic research communities to steer the evolution of science communication into the 21st century. For more information, please visit: (www.frontiersin.org). For online articles, please provide full citation and a link to the study, which is available for anyone to read free of charge. The study will be published when the embargo lifts on the following url: http://www.frontiersin.org/Human_Neuroscience/10.3389/fnhum.2013.00053/abstractdoi: 10.3389/fnhum.2013.00053