Behavioural and Neurophysiological Correlates of Emotional Modulation of Exogenous Spatial Attention: Evidence from Inhibition Of Return.
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The cue validity effect and Inhibition Of Return (IOR) are attentional phenomena first observed in a spatial cueing task. The cue validity effect represents faster responses to validly cued compared to invalidly cued targets and IOR is associated with faster responses to invalidly cued compared to validly cued targets. In cue-target paradigms IOR is usually observed at 300 ms. SOAs and at shorter SOAs the cue-validity effect is found. In this study an attempt is made to study emotional modulation of both attentional effects on a behavioural and neurophysiological level. Participants conducted an emotional modified spatial cueing task while EEG was recorded. Instructed threat conditioning was applied to modulate the level of threat of the cue. Cues consisted of neutral faces and one face was paired to an aversive sound while the other face was paired to a neutral tone. ERPs locked to cues and targets were measured and one of the main aims of this study was to examine cue-locked EEG activity originating from medio-frontal areas at a 200-400 ms. time window. Based on previous research an attempt was made to delay the onset of IOR in order to examine emotional modulation of the cue validity effect and measure cue-locked EEG activity 200-400 ms. post-cue. The experiment consisted of four different conditions. Target localization and target discrimination was randomized between subjects and short (200 ms.) and long (400 ms.) SOAs were randomized within subjects. An effect of task on the onset of IOR was observed, with an earlier onset of IOR in the localization compared to the discrimination task. However, IOR was present in three conditions: at both SOAs in the localization task and at the long SOA in the discrimination task. No IOR or cue validity effect was present at the short SOA in the discrimination task. Several task parameters may have contributed to the failed attempt to sufficiently delay the onset of IOR. Emotional modulation of the cue-validity effect could thus not be assessed, so emotional modulation of the IOR effect was examined. A reduction in the amount of IOR was observed after presentation of the threat cue compared to the neutral cue. In the localization task IOR was reduced by faster reaction times to valid and slower reaction times to invalid targets following the threat cue. In the discrimination task IOR was reduced only by faster reaction times to valid targets. This difference my be induced by different attentional set adopted in localization and discrimination tasks or by differences in motor-related processes. The target-locked P1 showed an IOR effect with larger amplitudes to invalid compared to valid targets. No evidence was found for the involvement of early visual and attentional processes, represented by the P1 related to the cue and target, in relation to the reduction in IOR, suggesting that other processes may be involved. A significant stronger P2a amplitude, with a medio-frontal scalp distribution, in response to the threat cue compared to the neutral cue was observed. It is suggested that this may represent an attention selection mechanism located in the MFC sensitive not only to task-relevant items, but also to affective and motivational relevant stimuli.