Explicit attention interferes with selective emotion processing in human extrastriate cortex

BACKGROUND: Brain imaging and event-related potential studies provide strong evidence that emotional stimuli guide selective attention in visual processing. A reflection of the emotional attention capture is the increased Early Posterior Negativity (EPN) for pleasant and unpleasant compared to neutral images (~150–300 ms poststimulus). The present study explored whether this early emotion discrimination reflects an automatic phenomenon or is subject to interference by competing processing demands. Thus, emotional processing was assessed while participants performed a concurrent feature-based attention task varying in processing demands. RESULTS: Participants successfully performed the primary visual attention task as revealed by behavioral performance and selected event-related potential components (Selection Negativity and P3b). Replicating previous results, emotional modulation of the EPN was observed in a task condition with low processing demands. In contrast, pleasant and unpleasant pictures failed to elicit increased EPN amplitudes compared to neutral images in more difficult explicit attention task conditions. Further analyses determined that even the processing of pleasant and unpleasant pictures high in emotional arousal is subject to interference in experimental conditions with high task demand. Taken together, performing demanding feature-based counting tasks interfered with differential emotion processing indexed by the EPN. CONCLUSION: The present findings demonstrate that taxing processing resources by a competing primary visual attention task markedly attenuated the early discrimination of emotional from neutral picture contents. Thus, these results provide further empirical support for an interference account of the emotion-attention interaction under conditions of competition. Previous studies revealed the interference of selective emotion processing when attentional resources were directed to locations of explicitly task-relevant stimuli. The present data suggest that interference of emotion processing by competing task demands is a more general phenomenon extending to the domain of feature-based attention. Furthermore, the results are inconsistent with the notion of effortlessness, i.e., early emotion discrimination despite concurrent task demands. These findings implicate to assess the presumed automatic nature of emotion processing at the level of specific aspects rather than considering automaticity as an all-or-none phenomenon

The effect of neuroleptic medication on prepulse inhibition in schizophrenia patients : current status and future issues

RATIONALE: Prepulse inhibition (PPI) of the startle reflex is a powerful tool for investigating sensorimotor gating in both animals and humans. Evidence of impaired PPI in patients with schizophrenia suggests that PPI performance might serve as a promising model to investigate the neurobiological mechanisms of this disorder. Animal data show that experimentally induced PPI deficits can be removed by the administration of antipsychotic agents. Recent clinical studies suggest that neuroleptic medication is capable of improving deficient PPI performance in schizophrenia patients as well. OBJECTIVES: The present paper reviews the published data on PPI performance in schizophrenia patients, focussing on medication effects. Using a modified meta-analytic approach, the consistency of PPI deficits in schizophrenia patients across studies is explored. In particular, methodological issues of defining PPI deficits and assessing PPI improvements are considered. METHOD: Literature search produced 12 original studies that investigated PPI performance in schizophrenia patients using comparable experimental conditions. Percentage change scores were calculated to compare the actual amount of PPI observed in schizophrenia patients and healthy controls across studies. RESULTS: Results revealed that the amount of PPI in medicated schizophrenia patients was fairly consistent across all studies. For medicated schizophrenia patients, the amount of PPI varied between 30% and 65% for the critical lead intervals. Moreover, medicated patients showed around 20% less PPI than healthy controls. Whether these group differences were statistically significant depended on the composition of the control group that showed large variability across studies. CONCLUSIONS: To delineate the effects of neuroleptic medication on PPI performance more precisely, future research should not further rely on between-group comparisons. Rather, future clinical research should take advantage of longitudinal designs to disentangle state-dependent medication effects from more stable, trait-linked factors that contribute to PPI deficits in schizophrenia

In dubio pro defensio : Initial activation of conditioned fear is not cue specific

This study explored the time course of conditioned fear response expression. Two neutral male facial expressions served as conditioned stimuli (CS) in a differential trace conditioning that involved either an aversive (n = 14) or a nonaversive (n = 12) unconditioned stimulus (UCS) in a between-subjects design. Skin conductance response (SCR) to the CSs and startle response magnitudes to acoustic probes presented at early (250 ms) or late (1,750 ms) probe times after CS onset were measured. As expected, conditioned SCR discrimination was observed in both aversive and nonaversive learning, whereas the conditioned potentiation of the startle response was only observed for the aversive UCS condition. Interestingly, conditioned startle discrimination was specific for the later probe time. In contrast, conditioned fear potentiation of the startle response at the early probe time was equally pronounced for CS+ and CS-. These findings suggest that fear-eliciting neural structures are rapidly activated in fear learning, whereas the expression of inhibitory conditioning requires more time, presumably reflecting the involvement of cortical top down control processes

Fear acquisition requires awareness in trace but not delay conditioning

The present study explored fear acquisition in differential delay versus trace conditioning in regard to the potential role of the acquired contingency awareness. One of two neutral pictures (CS+) either coterminated with (delay group; n=32) or was followed by the aversive unconditioned stimulus (UCS) after CS offset (trace group; n=32), while startle blink and skin conductance responses (SCR) were measured. As expected, the acquisition of conditioned startle potentiation in delay conditioning was independent of contingency awareness. In contrast, fear-potentiated startle in trace conditioning was only observed for those participants who were aware of the CS-UCS contingencies. SCR conditioning was generally only obtained for aware participants. The present results suggest a more implicit learning process in delay fear conditioning, whereas the explicit acquisition of contingency awareness might be a prerequisite for trace fear conditioning

Attention and emotion : An ERP analysis of facilitated emotional stimulus processing

Recent event-related potential studies observed an early posterior negativity (EPN) reflecting facilitated processing of emotional images. The present study explored if the facilitated processing of emotional pictures is sustained while subjects perform an explicit non-emotional attention task. EEG was recorded from 129 channels while subjects viewed a rapid continuous stream of images containing emotional pictures as well as task-related checkerboard images. As expected, explicit selective attention to target images elicited large P3 waves. Interestingly, emotional stimuli guided stimulus-driven selective encoding as reflected by augmented EPN amplitudes to emotional stimuli, in particular to stimuli of evolutionary significance (erotic contents, mutilations, and threat). These data demonstrate the selective encoding of emotional stimuli while top-down attentional control was directed towards non-emotional target stimuli