With the exception of new teenage drivers, elderly drivers have the highest rate of accidents per miles driven. Furthermore, older drivers are more likely than younger ones to be involved in multi-vehicle crashes, particularly at intersections. In some cases, these trends have been thought to be the result of visual impairments caused by bodily aging. However, some research has suggested that the brain, not the eyes, may be at fault.
The middle temporal visual area of the cerebral cortex (MT) is the part of the brain responsible for motion perception. In a young, healthy human, the MT suppresses irrelevant background motion and allows the person to focus on more immediate, important motions of smaller objects in the foreground. Elderly people, by contrast, are better at perceiving background motion.
Researchers at the University of Rochester recently demonstrated that the MT is responsible for this effect by inhibiting subjects’ MT using a process called Transcranial Magnetic Stimulation (TMS), and then testing how well the subjects could identify motions of smaller and larger objects on a computer screen. The scientists found that while the MT was inhibited, subjects could identify the motion of large, background-like objects more easily than smaller, foreground-like objects. These results suggest that an impaired MT may be what causes better perception of background motion in older adults.
Interestingly, patients with psychiatric disorders such as schizophrenia and depression also perceive background motion more easily than foreground motion. This suggests that in the future, rather than asking subjective questions such as Do you have trouble concentrating? Or Have you lost interest or pleasure in most daily activities?, psychiatrists may be able to use motion-detection tests to identify individuals suffering from these disorders.
|Resources from Wiley on This Topic|
Schizophrenia: Current science and clinical practice
by Wolfgang Gaebel
Normal Binocular Vision: Theory, Investigation and Practical Aspects
by David Stidwill and Robert Fletcher
1. “Older Drivers, Elderly Driving, Seniors At The Wheel.” SmartMotorist.com. May 2008. 11 April 2011. http://www.smartmotorist.com/traffic-and-safety-guideline/older-drivers-elderly-driving-seniors-at-the-wheel.html.
2. Owsley, C. (1998). Visual Processing Impairment and Risk of Motor Vehicle Crash Among Older Adults JAMA: The Journal of the American Medical Association, 279 (14), 1083-1088 DOI: 10.1001/jama.279.14.1083
3. Tadin D, Silvanto J, Pascual-Leone A, & Battelli L (2011). Improved motion perception and impaired spatial suppression following disruption of cortical area MT/V5. The Journal of neuroscience : the official journal of the Society for Neuroscience, 31 (4), 1279-83 PMID: 21273412