Depression, Suicide, and Performance Monitoring: Identifying Neuroelectric Markers of Suicidal Behavior

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Kaylie Carbine and Michael Larson, Psychology and Neuroscience

Introduction

From 2000-2009, suicide mortality rates increased by 15% (Rockett, et al., 2012) and 98% of individuals who complete suicide have diagnosable psychopathology (Bertolote, Fleischmann, De Leo, & Wasserman, 2003). Individuals at risk for suicide exhibit cognitive impairments in decision-making and problem-solving abilities (Pollock & Williams, 2004; Jollant, et al., 2005). These cognitive deficits may be related to deficits in performance monitoring. Performance monitoring is the ability to continually assess behavior in order to make adjustments and improve performance. Performance monitoring is mediated by the anterior cingulate cortex (ACC), which is related to cognitive control abilities. Furthermore, suicidal thoughts and behaviors are associated with abnormalities in the ACC (Mann, 2003). However, no known studies have examined if suicide risk is related to neuroelectric indices of performance monitoring. Also, neural indices in performance monitoring in individuals with major depressive disorder (MDD) are inconsistent. Suicide risk may moderate the performance monitoring discrepancies seen in individuals with MDD.

Neural indices of performance monitoring can be measured via event-related potentials (ERPs), which are changes in the brain’s electrical waveforms due to responses towards stimuli (Luck, 2005). We looked at three specific ERPs involved in performance monitoring processes: the error-related negativity (ERN), the correct-related negativity (CRN), and the post-error positivity (Pe). The ERN is a negative-going ERP that occurs 100ms after an erroneous response and reflects reinforcement learning, early error detection, or detection of response conflict (Falkenstein, Hohnsbein, Hoormann, & Banke, 1991; Holroyd & Coles, 2002; Yeung, Botvinick, & Cohen, 2004). The CRN is a negative-going ERP, occurring 100ms after a correct response and reflects overall performance-monitoring, emotional reactions toward a correct response, and error processing on correct trials when accuracy is uncertain (Pailing & Segalowitz, 2004; Vidal, Hasbroucq, Grapperon, & Bonnet, 2000). The Pe is a positive-going ERP that occurs 200-400ms after an incorrect response and reflects an affective response to a conscious error and later error processing (Nieuwenhuis, Ridderinkhof, Blom, Band, & Kok, 2001; Overbeek, Nieuwenhuis, & Ridderinkhof, 2005). Abnormalities in these ERPs may help distinguish between different cognitive processes of individuals at risk for suicide and those who are not. Specifically, we hypothesized that individuals who endorsed suicidal ideation will exhibit decreased ERN, CRN, and Pe amplitudes relative to individuals who did not endorse suicidal ideation and healthy controls.

Methodology

To elicit and measure ERPs, all participants (n=153) completed a modified Flanker task while wearing a 128-electrode sensor EEG net. In the task, participants see five arrows and are asked to identify the direction of the middle arrow for congruent (< < < < <) or incongruent (< < > < <) trials; 55% of trials were incongruent and 45% congruent. All participants had to have at least 15 useable error trials to be included in analyses. EEG data was re-referenced to an average reference off-line, cleaned for eye movement and extremely high voltages (>100μV) and digitally low-pass filtered at 30Hz.

All psychiatric diagnoses were completed by a health care provider and confirmed by the Mini-International Neuropsychiatric Inventory (MINI). The Suicidality Module of the MINI was used to assess suicide risk in participants. An IRB-approved protocol in case of current suicidality was in place and there were no adverse events during the research. All participants were free of neurological diseases, psychotic disturbances, bipolar disorder, psychotropic medication changes within the last two months, reported history of alcohol or substance abuse, a learning disability, or attention deficit/hyper activity disorder. Data were analyzed using three-group (MDD-suicide, MDD-no suicide, controls) one-way ANOVAs to examine the differences in the ERN, CRN, and Pe.

Results

Twenty-one participants were diagnosed with MDD and at risk for suicide (mean age=21.46, SD=2.66); 26 participants were diagnosed with MDD and not at risk for suicide (mean age=21.92, SD=2.10); 106 participants were healthy controls (mean age=20.90, SD=4.52). Whereas ERN (F[2,150]=0.13, p=.88) and Pe (F[2,150]=0.65, p=.52) amplitudes did not significantly differ between groups, CRN amplitude did differ between groups (F[2,150]=4.5, p=.01). Post hoc Tukey HSD analyses showed individuals with MDD at risk for suicide had a more negative CRN amplitude than healthy controls (p=.02).

Discussion

Individuals with MDD at risk for suicide showed no differences in ERN and Pe amplitudes compared to individuals with MDD not at risk for suicide and healthy controls; individuals at risk for suicide may not exhibit differences when specifically monitoring and processing error-trials. However, individuals with MDD at risk for suicide had a more negative CRN amplitude compared to healthy controls, suggesting individuals at risk for suicide may exhibit differences in overall performance monitoring, specifically overactive performance monitoring during correct-trials. Overactive correcttrial performance monitoring suggests individuals at risk for suicide may have difficulty differentiating between when they have made a correct response and when they have made a mistake (Olvet, Klein, & Hajcak, 2010). Future research may wish to examine performance monitoring exclusively in individuals who have attempted suicide to see if CRN amplitudes are related to increased risk of attempting suicide.

Conclusion

We aimed to examine if individuals at risk for suicide exhibited differences in neural indices of performance monitoring relative to individuals not at risk for suicide and healthy controls. Individuals at risk for suicide did not show differences in performance monitoring specifically during error-trials, although they did exhibit overactive correcttrial performance monitoring. Future research should further investigate performance monitoring differences in individuals who have attempted suicide.

References

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