In Brief

Psychologists may have discovered the key to unlocking the mystery of why cognitive difficulty increases with age: New research shows that younger and older individuals differ in how they process contextual cues due to differences in dopamine function in the prefrontal cortex.

In the December Journal of Experimental Psychology: General (Vol. 130, No. 4), Todd S. Braver, PhD, and Deanna M. Barch, PhD, both of Washington University, and their colleagues discuss a computational model of context processing they developed, which suggests that lower levels of dopamine in the prefrontal cortex account for a breakdown in cognitive control. With sufficient dopamine in the prefrontal cortex, people are able to process context for a thought, memory or behavior. With less dopamine, which is the case in aging adults, people experience difficulty with attention, inhibition and memory.

Using a series of trials that required cognitive control, the researchers compared the performance of 175 young adults (ages 18 to 29) and 81 older adults (ages 65 to 85). By comparing results from these trials, the researchers found that older adults had impaired context processing and fewer "false alarms" because their impaired processing inhibited them from making a response.

While increased task difficulty did not affect performance, interference brought out age-related differences, further establishing the role of context processing in attention, active memory and inhibition. These results suggest a deficit in the ability to "properly represent, maintain and update task-relevant context" as the basis for a range of age-related cognitive declines, the authors say.