Stimulus-Locked and Response-Locked ERP Correlates of Spatial Inhibition of Return (IOR) in Old Age

Abstract

Behavioral research has shown that Inhibition of Return (IOR) is preserved in old age although at longer time intervals between cue and target, which has been interpreted as reflecting a later disengagement from the cue. A recent event-related potential (ERP) study attributed this age-related pattern to an enhanced processing of the cue. Previous ERP research in young samples indicates that target and response processing are also affected by IOR, which makes interesting to study the ERP correlates of IOR from cue presentation to response execution. In this regard, in the present study stimulus-locked (cue-locked and target-locked) and response-locked ERPs were explored in healthy young and older participants. The behavioral results indicated preserved IOR in the older participants. The cue-locked ERPs could suggest that the older participants processed the cue as a warning signal to prepare for the upcoming target stimulus. Under IOR, target-locked ERPs of both age groups showed lower N1 amplitudes suggesting a suppression/inhibition of cued targets. During the P3 rising period, in young subjects a negative shift (Nd effect) to cued targets was observed in the lower visual field (LVF), and a positive shift (Pd effect) in the upper visual field. However, in the older group the Nd effect was absent suggesting a reduction of attentional resolution in the LVF. The older group showed enhanced motor activation to prepare correct responses, although IOR effects on response-locked lateralized readiness potential LRP indicated reduced response preparation to cued targets in both age groups. In general, results suggest that the older adults inhibit or reduce the visual processing of targets appearing at cued locations, and the preparation to respond to them, but with the added cost of allocating more attentional resources onto the cue and of maintaining a more effortful processing during the sequence of stimuli within the trial.