Electrophysiological evidence for inhibition of return effect in exogenous orienting

Exploring the temporal dynamics of inhibition of return using steady-state visual evoked potentials

Inhibition of return is characterized by delayed responses to previously attended locations when the interval between stimuli is long enough. The present study employed steady-state visual evoked potentials (SSVEPs) as a measure of attentional modulation to explore the nature and time course of input- and output-based inhibitory cueing mechanisms that each slow response times at previously stimulated locations under different experimental conditions. The neural effects of behavioral inhibition were examined by comparing post-cue SSVEPs between cued and uncued locations measured across two tasks that differed only in the response modality (saccadic or manual response to targets). Grand averages of SSVEP amplitudes for each condition showed a reduction in amplitude at cued locations in the window of 100-500 ms post-cue, revealing an early, short-term decrease in the responses of neurons that can be attributed to sensory adaptation, regardless of response modality. Because primary visual cortex has been found to be one of the major sources of SSVEP signals, the results suggest that the SSVEP modulations observed were caused by input-based inhibition that occurred in V1, or visual areas earlier than V1, as a consequence of reduced visual input activity at previously cued locations. No SSVEP modulations were observed in either response condition late in the cue-target interval, suggesting that neither late input- nor output-based IOR modulates SSVEPs. These findings provide further electrophysiological support for the theory of multiple mechanisms contributing to behavioral cueing effects.

Human electrophysiology reveals delayed but enhanced selection in inhibition of return

Visual environment tends to be stable over the short run. An immediately visited location often doesn't provide new information and can be safely inhibited, as exemplified by inhibition of return (IOR)-attention takes longer to return to a previously cued location. Attention selection at this inhibited location has been widely characterized as inferior, in which the target at the cued location has diminished salience, with lower rate of accumulation in the priority map for attention selection. We demonstrate here that an electrophysiology index of visual selection-the N2pc component-is delayed but enhanced at the cued than uncued location, and this enhancement in the N2pc amplitude predicts reduction in the behavioral IOR effect. By isolating a pure target N2pc, these results reveal an active attention enhancement mechanism that facilitates adaptive allocation of attention when a target appears at a previously cued location, potentially acting as a compensation mechanism for inhibition.

ERP-study on the time course of disgust-motivated spatial avoidance

Recently, we showed that disgusting sound cues direct spatial attention away from the location of their origin to the opposite location indicating spatial disgust avoidance (Zimmer et al., 2015, Psychophysiology; 2016, Neuroimage). However, in these studies, we had solely used an inter-stimulus interval (ISI) of 200-300 ms, leaving unclear how disgust avoidance develops over time. Studies have shown that spatial attraction due to anger persists longer when induced by auditory rather than visual stimuli. In the present ERP-study, one of two laterally presented sounds (neutral/disgust) cued a laterally presented visual target. ISIs varied from short (50-150 ms) over middle (350-450 ms) to long (650-750 ms). For disgust stimuli, response times were longer for invalidly cued targets compared to validly cued targets, reflecting disgust avoidance. There was an increased P3 amplitude for validly versus invalidly cued targets consistent with disgust avoidance. In contrast, in the neutral condition, we found evidence of inhibition of return (IOR), as we observed a reversal of the usual validity effect from short to long ISI in the behavioral data and on the P1-component. These results indicate that spatial avoidance motivated by auditory disgust persists over time, presumably enforced by emotional rather than general attentional processes.

Cognitive control activity is modulated by the magnitude of interference and pre-activation of monitoring mechanisms

The Simon task is used to study interference from irrelevant spatial information. Interference is manifested by longer reaction times when the required response -based on non-spatial features- is spatially incompatible with stimulus position. Interference is greater when incompatible trials are preceded by compatible trials (compatible-incompatible sequence) than when they are preceded by incompatible trials (incompatible-incompatible sequence). However, the relationships between spatial attention, interference and cognitive control have not been investigated. In the present study, we distinguished three experimental conditions according to sequential effects: same mappings (SM, compatible-compatible/incompatible-incompatible sequences: low interference), opposite mappings (OM, compatible-incompatible/incompatible-compatible sequences: high interference) and unrelated mappings (UM, central-compatible/central-incompatible sequences: intermediate interference). The negativity central contralateral (N2cc, a correlate of prevention of spatial response tendencies) was larger in OM than in SM, indicating greater cognitive control for greater interference. Furthermore, N2cc was larger in UM than in SM/OM, indicating lower neural efficiency for suppressing spatial tendencies of the response after central trials. Attentional processes (negativity posterior contralateral) were also delayed in UM relative to SM/OM, suggesting attentional facilitation by similar sets of attentional shifts in successive trials. Overall, the present findings showed that cognitive control is modulated by the magnitude of interference and pre-activation of monitoring mechanisms.

ERP evidence for spatial attention being directed away from disgusting locations

When we change sidewalks because we see vomit or dog feces, we are avoiding disgusting stimuli. However, it is unclear how we shift spatial attention itself away from disgusting stimuli. In the present study, we used a multisensory spatial-cuing paradigm as a tool to test if a disgusting sound is avoided by redirecting visual attention to the opposite side. Our results show that behavioral responses as well as the P3 component indicated an inverse validity effect when cued by disgust. Validity differences on the P3 were increased ipsilaterally instead of contralaterally over visual electrode sites. In contrast, the N1 component, time-locked to sound cues, indicated the typical contralateral attentional arousal effect. Thus, disgusting sound cues first attract attention toward their location and later, after the processing of their emotional content, direct spatial attention away from the location of their origin to the opposite location.

Does response selection contribute to inhibition of return?

Inhibition of return (IOR) means delayed responses for targets at a cued compared to targets at an uncued location. It is assumed to reflect delayed reallocation of attention toward a previously attended location. Besides an attentional mechanism, IOR could also be due to a cue-evoked inhibition to respond toward a cued target. In the present study, IOR with simple, compatible, and incompatible choice responses was compared and tracked by means of event-related EEG activity. IOR was amplified with simple responses but did not differ between compatible and incompatible responses. Attention-related ERP correlates were constant across cue target onset asynchronies as were, in part, behavioral effects. Early, rather sensory ERP components varied with time, reflecting sensory or attentional interaction of cue and target processing. None of these effects varied with response requirements, indicating that response selection does not contribute to IOR in manual choice response tasks.

Just passing through? Inhibition of return in saccadic sequences

Responses tend to be slower to previously fixated spatial locations, an effect known as “inhibition of return” (IOR). Saccades cannot be assumed to be independent, however, and saccade sequences programmed in parallel differ from independent eye movements. We measured the speed of both saccadic and manual responses to probes appearing in previously fixated locations when those locations were fixated as part of either parallel or independent saccade sequences. Saccadic IOR was observed in independent but not parallel saccade sequences, while manual IOR was present in both parallel and independent sequence types. Saccadic IOR was also short-lived, and dissipated with delays of more than ∼1500 ms between the intermediate fixation and the probe onset. The results confirm that the characteristics of IOR depend critically on the response modality used for measuring it, with saccadic and manual responses giving rise to motor and attentional forms of IOR, respectively. Saccadic IOR is relatively short-lived and is not observed at intermediate locations of parallel saccade sequences, while attentional IOR is long-lasting and consistent for all sequence types.