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.

Spatial Inhibition of Return promotes changes in response-related mu and beta oscillatory patterns

“…Previous ERP results in our laboratory with the same task employed in the present experiment have shown IOR-related reductions in the amplitude of R-LRP also in the LVF that have been related to reduced/inhibited response preparation to spatially cued targets (see Amenedo et al, 2014). Taking into account the above studies in the context of somatosensory spatial attention and mu modulations, and our previous response-locked ERP results, the synchronization of preresponse mu rhythm observed in the present study under spatial IOR could be related to an attention-driven reduction of somatomotor processing that leads to power increases prior to the execution of responses to target stimuli that are presented at previously cued locations and whose visual processing has been reduced (see also Gutiérrez-Domínguez et al, 2014).…”

“…In the research context of the present results, the visual field has been found to be an important factor affecting IOR effects on visual and response-related ERP activity with the same task design (Amenedo et al, 2014;Gutiérrez-Domínguez et al, 2014). In those studies, when comparing location-cued trials with the uncued trials, the target-locked ERPs showed significant spatial IOR effects that differed between visual fields in several components.…”

“…The explanation of such late reduction (or inhibition) of motor activity observed in the beta rhythm in the UVF could be associated with the vertical asymmetries observed in many studies employing attention tasks, including two previous studies in the IOR context (Amenedo et al, 2014;Gutierrez-Domínguez et al, 2014) as discussed below.…”

“…They found IOR effects on T-LRP latency but not on R-LRP latency, concluding that IOR may not be related to response preparation timing but only to pre-motor selection processes. More recently, Amenedo et al (2014) examined the amplitude changes in R-LRP, and found that IOR was related to a significant amplitude reduction of this component when responding to previously cued targets, suggesting that response preparation could be affected when responding to targets presented at previously cued locations.…”

“…Due to the well established effects of stimulus-response spatial compatibility on response processing (see Hommel, 2011 for a review), and to the possible interactions between these effects and IOR effects (see Ivanoff et al, 2002 for a review) the stimuli were presented along the vertical axis of the visual field. Moreover, due to the frequently reported existence of visual asymmetries when the stimuli are presented along the vertical meridian (Rezec and Dobkins, 2004;Amenedo et al, 2007;Karim and Kojima, 2010;Thomas and Elias, 2011), and to previous results showing the existence of such asymmetries on the effects of spatial IOR on stimulus-locked and on responselocked ERPs (Amenedo et al, 2014;Gutiérrez-Domínguez et al, 2014) the data from each visual field were analyzed separately. With this design, we aimed at exploring IOR effects on EEG activity related to response processing by analyzing the spatial and temporal changes in frequency oscillations between 2 and 40 Hz related to response preparation and execution.…”