Age-related valence-based reversal in recruitment of medial prefrontal cortex on a visual search task

Abstract

Previous behavioral research has revealed a positivity effect that occurs with aging, with older adults focusing more on positive information and less on negative emotional stimuli as compared to young adults. Questions have been raised as to whether this effect exists in the rapid detection of information or whether it operates only at later stages of processing. In the present study, we used eye-tracking and neuroimaging methodologies to examine whether the two age groups accomplished the detection of emotional information on a visual search task using the same mechanisms. Eye-tracking results revealed no significant age differences in detection or viewing time of emotional targets as a function of valence. Despite their general similarity in task performance, neuroimaging results revealed an age-related valence-based reversal in medial prefrontal cortex (MPFC) activity, with detection of negative compared to positive targets activating the MPFC more for younger adults, and detection of positive compared to negative targets activating the MPFC more for older adults. These results suggest that age-related valence reversals in neural activity can exist even on tasks that require only relatively automatic processing of emotional information.

Keywords:

• Aging
• Emotion
• fMRI
• Medial prefrontal cortex
• Visual search

Acknowledgments

This research was supported by grant BCS 0542694 from the National Science Foundation and by grants from the Dana Foundation and the Searle Scholars Program (to EAK). We thank Keely Muscatell and Pooja Patnaik for assistance with participant recruitment and testing.

Notes

¹We have chosen not to extensively discuss the behavioral results from the neuroimaging experiment because the MRI-compatible button-box set-up did not allow for sensitive recordings of reaction times. Participants were required to use a button-box that was placed along their leg, which is an unfamiliar response arrangement for most participants. Additionally, the button-box interface was not equipped with ms timing precision. Indeed, overall button press reaction times (RTs) were slower for the data collected in Experiment 2 compared to Experiment 1, on the order of approximately 500 ms, and variability in RT was greater. We have included the participants' behavioral RTs primarily because they would provide information about the duration of time for which the arrays had appeared on the screen (since, as in most visual search tasks, the array remained on the screen until participants made a button press). However, given the unreliable nature of this response method, we are hesitant to draw conclusions about the patterns of results of these data.