Intact motivated attention in schizophrenia: Evidence from event-related potentials
Introduction
People with schizophrenia often show diminished emotional expression and pleasurable experiences based on clinical rating scales (Blanchard et al., 2011). However, when directly exposed to evocative stimuli (e.g., pictures, foods), patients show normal emotion-modulated experiential, cardiovascular, electrodermal, and startle eyeblink responses (Kring and Moran, 2008). Motivationally relevant stimuli rarely present themselves in this way in daily life; they are often incidental to the primary tasks we are performing. In healthy subjects, incidental emotional stimuli naturally capture attention, an adaptive process called “motivated attention” (Bradley, 2009). Adaptive functioning, however, requires an optimal balance: incidental emotional stimuli need to capture attention but not deplete the resources required for ongoing goal-directed pursuits. The current study used an event-related potential (ERP) paradigm to evaluate processing of task irrelevant emotional stimuli in schizophrenia.
In healthy subjects, two ERPs, the early posterior negativity (EPN) and late positive potential (LPP), are larger for both pleasant and unpleasant compared with neutral pictures, reflecting increased attention to motivationally relevant stimuli (see Hajcak et al., 2010). The EPN (200–300 ms) reflects early and relatively automatic selective attentional processing, whereas the LPP (400–1000 ms) reflects more sustained allocation of attentional resources. Consistent with the concept of motivated attention, the EPN and LPP are larger for emotional than neutral pictures even when the valence of pictures is irrelevant to the primary task to which attention is directed (Hajcak et al., 2010).
Recently, we found patients showed generally normal early and late ERP's to emotional versus neutral pictures during a task in which subjects attended to the pictures (Horan et al., 2010). However, we are not aware of any prior studies that examined whether patients also show intact ERPs to task-irrelevant emotional images. To address this question, the current study used a modified visual P300 task modeled on Fichtenholtz et al. (2004) that involved rare target letter stimuli intermixed with irrelevant images of varying emotional content. A handful of behavioral and functional magnetic resonance imaging (fMRI) studies show mixed evidence of intact versus impaired automatic emotional processing in schizophrenia (e.g., Dichter et al., 2010, Roux et al., 2010, Schwartz et al., 2010, Strauss et al., 2011); our prior ERP study led to the prediction that patients would show a larger EPN and LPP to task-irrelevant emotional versus neutral stimuli, similar to healthy controls.
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Participants
Thirty-five outpatients with schizophrenia based on the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID; First et al., 1996). Patients were medicated at clinically determined dosages. Psychiatric symptoms were rated using the expanded 24-item Brief Psychiatric Rating Scale (BPRS; Kopelowicz et al., 2008). Twenty-five healthy controls from the local community were screened with the SCID and SCID-II (Cluster A). Procedures were approved by the local Institutional Review Board.
ERP's to pictures
Grand average ERPs are presented in Fig. 2, Fig. 3, and mean ERP amplitudes are presented in Table 2. For the EPN, a 3 (Valence) × 2 (Group) repeated-measures ANOVA revealed a significant Valence effect. Compared to neutral pictures, LPP was significantly more positive for both unpleasant, t(60) = 5.23, p < .001, and pleasant pictures, t(60) = 4.38, p < .001, which did not significantly differ from each other, t(60) = 1.39, p > .05. The Group and Interaction effects were not significant, indicating a similar
Discussion
This study found normal early and late emotion-modulated ERPs in schizophrenia. Hence, the results from our earlier study (Horan et al., 2010) extend to processing task-irrelevant emotional stimuli. Automatic “grabbing” of attention by, and sustained processing of, emotional stimuli may reflect yet another area of relatively preserved emotion processing in schizophrenia. Our paradigm also allowed us to evaluate performance and ERPs in the target detection task where attention was directed. The
Role of funding sources
This work was supported by a NARSAD Young Investigator Award (to WPH) and the National Institute of Mental Health (MH082782 to WPH; MH065707, MH43292 to MFG). Funding sources had no role in study design or in the collection, analysis and interpretation of data; or in the writing of this report.
Contributors
Drs. Horan, Hajcak, and Green designed the study. All authors contributed to data analysis and intepretation. Dr. Horan wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.
Conflict of interest
None.
Acknowledgments
The authors would like to thank and acknowledge the following people who contributed to the data collection for the study: Mark McGee, Crystal Gibson, Cory Tripp, Katie Weiner, and Poorang Nori.
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