Clumsiness linked to brain changes
Clumsiness in children is normal and often laughed about, but clumsiness in older adults is more annoying and not so funny.
While normal, increased clumsiness as part of the aging process is triggered by age-related breakdowns in agility, vision and other physical abilities, which may be caused by changes in the mental frame of reference that older adults use to visualize nearby objects.
"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 Richard Abrams, PhD, professor of psychology in Arts & Sciences.
"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," Abrams added.
The study, published in the journal Psychological Science, was also co-authored by Emily K. Bloesch, PhD, a postdoctoral teaching associate at Central Michigan University and Christopher C. Davoli, PhD, a postdoctoral psychology researcher at the University of Notre Dame.
The researchers tested and compared both young and old adult participants by administering a series of simple tasks involving hand movements. The results showed that young participants in this study adopted an attentional reference frame centered on the hand, while older participants adopted a reference frame centered on the body.
As the researchers explained, young adults have been shown to use an "action-centered" reference frame that is sensitive to the movements they are making; thus, when young people move their hands to pick up an object, they remain aware of and sensitive to potential obstacles along the movement path.
On the other hand, older adults tend to focus more attention on objects that are closer to their bodies – regardless of if they’re on the action path or not.
"We showed in our paper that older adults do not use an ‘action centered’ reference frame. Instead they use a ‘body centered’ one," Bloesch said. "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."
This study’s findings are consistent with prior research that has confirmed age-related physical declines in numerous areas of the brain responsible for hand-eye coordination. Older adults exhibit volumetric declines in the parietal cortex and intraparietal sulcus, as well as white-matter loss in the parietal lobe and precuneus of the brain. Such declines may make use of an action-centered reference frame difficult or impossible.
"These three areas 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. These neurological changes in older adults 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," the study finds.
With the aging of the baby boom generation, research on these issues is becoming increasingly important. According to research, an estimated 60 to 70 percent of the elderly population reports having difficulty with daily activities, such as eating and bathing, and many show deficiencies in performing goal-directed hand movements.
Accordingly, the researchers suggest that knowing more about these aging-related changes in spatial representation may eventually inspire options for skills training and other therapies to help seniors compensate for the cognitive declines that influence hand-eye coordination.
SOURCE: E. K. Bloesch, C. C. Davoli, R. A. Abrams. Age-Related Changes in Attentional Reference Frames for Peripersonal Space. Psychological Science, 2013; 24 (4): 557 DOI: 10.1177/0956797612457385