Does cerebral activity change in middle-aged adults in a visual discrimination task?

The purpose of this study was to assess changes in cerebral activity in middle-aged adults (MA: 50 years) compared to young adults (YA: 20 years). Subjects had to compare the duration or the intensity of a visual stimulus with a previously memorized standard. Evoked potentials were recorded, and a dipole model (obtained from PET data on young adults) was applied for fitting late-latency components. MA performance was poorer than YA performance. Task-specific ERP late components were found (P3 in intensity, CNV in duration), but P3 had a lower amplitude and CNV was less frontal in MAs compared to YAs. The activity of the dipoles that generate late components - cuneus in the intensity task, right frontal in the duration task, and anterior cingulate in both tasks-was less ample or less peaked in MAs than in YAs. This study characterizes neurobiological effects of aging that may already be visible during midlife.