redOrbit Staff & Wire Reports – Your Universe Online
Often attributed to age-related decay in vision and physical prowess, incidents of clumsiness in seniors could actually be caused by changes in the brain, researchers from Washington University in St. Louis claim in a new study.
Incidents in which older men and women have difficulty reaching for and/or grasping things, such as inability to dial a phone of knocking over a glass while attempting to grab a different object, could be the result of changes in the mental frame of reference that these individuals use to visualize nearby objects, the researchers explained.
“Reference frames help determine what in our environment we will pay attention to and they can affect how we interact with objects, such as controls for a car or dishes on a table,” said study co-author Dr. Richard Abrams, a professor of psychology in Arts & Sciences at the university. “Our study shows that in addition to physical and perceptual changes, difficulties in interaction may also be caused by changes in how older adults mentally represent the objects near them.”
When asked to perform a series of simple tasks that involve hand movements, younger people participating in the study adopted an attentional reference frame that centered on that part of the body. However, older subjects adopted a reference frame that centered on the body, not on the hand, the authors explained in research published in the journal Psychological Science.
Younger men and women have been known to use a reference frame that is “action-centered,” which means that it is sensitive to the movements they are making. For this reason, when these individuals move their hands to pick up an object, they maintain their awareness of objects potentially blocking their movement path. Conversely, seniors typically pay more attention to the objects closer to their body, even if they are not on the action path.
“We showed in our paper that older adults do not use an ℠action centered´ reference frame. Instead they use a ℠body centered´ one,” explained lead author, Dr. Emily K. Bloesch, a former Washington University student who now serves as a postdoctoral teaching associate at Central Michigan University. “As a result, they might be less able to effectively adjust their reaching movements to avoid obstacles — and that´s why they might knock over the wine glass after reaching for the salt shaker.”
The study supports previous research which has documented age-related physical declines in multiple regions of the brain which are responsible for hand-eye coordination, the university said. Older adults demonstrate “volumetric declines” in both the parietal cortex and intraparietal sulcus, and they also lose white matter in the parietal lobe and precuneus. This decay could prevent them from using an action-centered reference frame.
Those areas, the authors noted, “are highly involved in visually guided hand actions like reaching and grasping and in creating attentional reference frames that are used to guide such actions.”
Furthermore, these specific neurological changes in older men and women “suggest that their representations of the space around them may be compromised relative to those of young adults and that, consequently, young and older adults might encode and attend to near-body space in fundamentally different ways,” said the study, which was supported by a grant from the National Institute on Aging.