Attentional bias in high- and low-anxious individuals: evidence for threat-induced effects on engagement and disengagement.

Attentional bias to threatening visual stimuli (words or pictures) is commonly present in anxious individuals, but not in non-anxious people. There is evidence to show that attentional bias to threat can be induced in all individuals when threat is imposed by threat not of symbolic nature, but by cues that predict aversive stimulation (loud noise or electric shock). However, it is not known whether attentional bias in such situations is still influenced by individual differences in anxiety. This question was addressed in two experiments using a spatial cuing task in which visual cues predicted the occurrence of an aversive event consisting of a loud human scream. Speeded attentional engagement to threat cues was positively correlated with trait anxiety in Experiment 1. Experiment 2 showed that speeded attentional engagement was present only in participants selected for high anxiety but not in low-anxious participants. In both experiments, slower disengagement from threat cues was found in all participants, irrespective of their trait anxiety levels.

Startle potentiation in rapidly alternating conditions of high and low predictability of threat.

Effects of predictability of threat on potentiation of the startle reflex were investigated by presenting participants with predictable and unpredictable electric shocks. Shocks were presented either paired with a visual cue (paired condition) or unrelated to the presentation of the visual cues (unpaired condition). In contrast to previous slower-paced studies, conditions alternated at a rapid rate: each context lasted 8.5 s and within these contexts the visual cues had a duration of 1.5 s. Results replicated previous findings: in the predictable condition, startle responses were augmented by a threat-signaling stimulus, and startle responses in the unpredictable condition were larger than in a neutral condition in which no shocks were presented. In all three conditions, visual stimuli that did not carry information about when a shock could be presented augmented startle reactivity. A control experiment showed that the effects of threat on the startle response could not be ascribed to attention and that the effects of the lead stimuli that did not signal threat are likely to be unrelated to the effects of threat. These results show that the fear system is modulated dynamically as a function of rapidly changing information about threat and emphasize the role of predictability of an aversive stimulus in the distinction between cue-specific and contextual fear.

Spatio-temporal dynamics of top-down control: directing attention to location and/or color as revealed by ERPs and source modeling.

This study investigated the nature and dynamics of the top-down control mechanisms that afford attentional selection using event-related potentials (ERPs) and dipole-source modeling. Subjects performed a task in which they were cued to direct attention to color, location, a conjunction of color and location or no specific feature on a trial-by-trial basis. Overall, similar ERP patterns were observed for directing attention to color and location, suggesting that spatial and non-spatial attention rely to a great extent on similar control mechanisms. The earliest attention-directing effect, at 340 ms, was localized to ventral posterior cortex and may reflect processes by which the cue is linked to its associated feature. Only late in the cue-target interval, differences in ERP were observed between directing attention to color and location. These originated from anterior and ventral posterior areas and may represent differences in, respectively, maintenance and perceptual biasing processes. The ventral posterior sources estimated for these late effects of directing attention to location and color were located posterior to those estimated for the modulatory effects of, respectively, spatial and non-spatial attention. This suggests that the precise neural populations involved in perceptual biasing and attentional modulation may differ. Conjunction cues initially elicited less posterior positivity than color and location cues, but evoked greater central positivity from 540 ms on. This central effect may reflect feature integration or ongoing processes related to cue-symbol translation. These results extend our understanding of the spatio-temporal dynamics of top-down attentional control.

Performance monitoring in obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is associated with hyperactivity of brain structures involved in performance monitoring. It has been proposed that this pathophysiology results in the generation of inappropriate or excessive internal error signals, giving rise to the characteristic symptoms of OCD. We measured an electrophysiological correlate of performance monitoring, error-related negativity (ERN), to study whether OCD patients exhibit enhanced brain activity associated with errors and negative performance feedback. We found that OCD patients (n=16) and healthy control participants (n=16) did not differ in the amplitude of the ERN associated with errors and negative feedback in a probabilistic learning task. The discrepancy between these results and the results from previous studies is discussed.

Reinforcement-related brain potentials from medial frontal cortex: origins and functional significance.

The development of the field of cognitive neuroscience has inspired a revival of interest in the brain mechanisms involved in the processing of rewards, punishments, and abstract performance feedback. One fruitful line of research in this area was initiated by the report of an electrophysiological brain potential in humans that was differentially sensitive to negative and positive performance feedback [J. Cogn. Neurosci. 9 (1997) 788]. Here we review current knowledge regarding the neural basis and functional significance of this feedback-evoked 'error-related negativity' (ERN). Our review is organized around a set of predictions derived from a recent theory, which holds that the ERN is associated with the arrival of a negative reward prediction error signal in anterior cingulate cortex.

Generating spatial and nonspatial attentional control: An ERP study.

The present study used event-related potentials and dipole source modeling to investigate dimension specificity in attentional control. Subjects performed cued attention tasks in which the task-relevant information (a) was always the same, (b) varied between features within the same dimension, or (c) varied between features of two different dimensions. Thus, both demands on control processes involved in generating an attentional set and the dimension (color or location) of the task-relevant feature were varied. Attentional control was associated with a dorsal posterior positivity starting at 260 ms postcue, which was stronger over left posterior scalp regions from 580 ms onward, especially when color was task relevant. This positivity likely reflects generic processes involved in the generation of an attentional set that were followed in time by dimension-specific processes related to the persistence of the task-relevant information in working memory.