Although the researchers cannot say for sure, one theory that needs further study is that the extra activity in older adults is probably compensation for age-related changes in brain volume or efficiency, according to Christy Marshuetz, assistant professor in the Department of Psychology and a co-author of the study.
The study included a dozen people 18- to 27-years-old, and an equal number of 61- to 80-year-olds. They were asked to remember three images of houses or three images of faces and then asked to decide if another image was from the original set. Functional magnetic resonance imaging was used to track neural changes during these tasks.
Marshuetz said it has been known for some time that there are different regions in the inferior temporal lobes of the brain that respond to faces and to photographs of houses. It is also well established that as humans age, both neural and cognitive function become less differentiated. But the data is sparse and previous studies have examined neural activity only during passive viewing.
In this study, the researchers examined age differences in neural specialization for "faces and places" in a working memory task. They hypothesized that even when consciously remembering specific items, older adults would show decreased specialization in the fusiform face area of the brain and the parahippocampal place area of the brain when compared with younger adults. The researchers also expected, and found, more activity in older adults in the frontal cortex and believe this activity is compensation for less differentiation in the visual cortex at the back of the brain.
"Our findings are the first to demonstrate decreased neural specialization in the ventral visual cortex in older adults, along with increased activations in the prefrontal cortex," Marshuetz said. "This underscores the importance of taking into account the connected and networked nature of the brain and its function in understanding human neural aging."
Co-authors include Doris Payer, Brad Sutton, Andy Hebrank, and Denise Park of the University of Illinois at Urbana-Champaign, and Robert Welsh of the University of Michigan.
Neuroreport 17 (5): 493-497 (April 3, 2006)