Supplemental Materials

Attentional Bias Temporal Dynamics in Remitted Depression

by A. Zvielli et al., 2016, Journal of Abnormal Psychology

Method

Participants

The RMDs were recruited from a Dutch medical center and regional outpatient psychiatric services. The control group of never-depressed individuals was recruited via local newspapers, online postings at the medical center’s website and a local training center.

Exclusion criteria for both groups were: Current depressive episode, current or lifetime bipolar disorder, schizophreniaandothercurrentorformerpsychoticdisorders, alcohol or substance abuse within the past 6 months, deafness, blindness, neurological disorder and sensorimotor disabilities limiting cognitive functions or computer use, and intellectual disability. Patients with a previous major depressive episode with psychotic features were allowed to participate. The study was approved by the Dutch central medical ethics review board (P04.0599C) and was performed in accordance with guidelines and regulations for human studies. This study was part of a larger study designed to study cognitive biases to genetic susceptibility for depression.

Procedure

Depression Assessment and Study Eligibility.

A psychiatrist was consulted before inclusion in case of recent recovery from a depressive episode with lingering depressive symptoms. Current use of psychotropic medication that might influence cognitive functioning was assessed by a psychiatrist. Number of past episodes was assessed during the diagnostic interview.

Attentional Bias Measurement.

Participants were asked to pay attention to a target (dot) on the computer screen while ignoring the preceding pair of pictures (selected from the Karolinska Directed Emotional Faces database; (Lundqvist, Flykt, & Ohman, 1998). Each pair depicted a unique individual with two different facial expressions: 20 pairs of sad and emotionally-neutral expressions and 20 pairs of happy and emotionally-neutral expressions (half male faces, half female faces). The 1000ms presentation of a face pair was preceded by a black fixation cross in the middle of the screen (for 500ms). Then, a small gray dot appeared on the screen location where one of the pictures was presented and remained on screen until the participant responded to its location. Participants were instructed to determine, as quickly and accurately as possible, whether the gray dot was on the left or right side of the computer screen by pressing one of two keys on a standard keyboard.

Participants were seated with their eyes ~50 cm from the monitor.Face gender (male/female), face emotion (happy/sad) and emotion-neutral face location (left/right) were equally counter-balanced across the task. Half of the trials (randomly ordered) were congruent trials (CT), in which the target (probe) was presented at the location of the emotional (happy/sad) face, and half were incongruent trials (IT), in which the target appeared at the location of the emotionally-neutral face.

Results

Data Preparation

We discarded dot probe task trials with incorrect responses (M %(SD) =0.71% (.91)). Of the remaining trials, statistical outliers (<200ms, >1500ms or >3SDs above or below individual’s SD) were also discarded (M % (SD) = 1.77% (1.71)). No other post-hoc data screening criteria were applied or tested.

Attentional Bias Computation

The pre-defined window size of 5 was the maximum for any possible match but not the common distance between matched trials, as the matching algorithm selects the most proximate match possible. Accordingly, the distance between matched trials was M(SD) = 2.0(0.16), such that the maximum of 5 was only rarely reached.

Parameters of AB dynamics – each reflecting a key feature of AB dynamics: (1) Mean TL-BSTOWARDS - Mean TL-BS > 0ms; (2) Mean TL-BSAWAY - Mean TL-BS < 0ms (3) Peak TL-BSTOWARDS - Maximum TL-BS. (4) Peak TL-BSAWAY - Minimum TL-BS (5) TL-BS Variability - Temporal stability/variability in the expression of AB towards and/or away over time (i.e., sum of distances between sequential TL-BS estimates / number of TL-BS estimates).

Analyses Ruling Out Alternative Explanations of Findings

Controlling for participant age. RMD participants age (M(SD)=47.74(11.98) years-old) were slightly older than the never depressed group (M(SD)=42.94(11.98) years-old) (t(408)=3.29, p <.001). Group status remained significantly associated with TL-BS parameters of AB dynamicsafter controlling for participant age (F(1,407) = 10.06 – 11.90 , p < .01, ηp2 = .024 – .028). A similar incremental effect beyond participant agewas also observed with respect to the association between number of depressive episodes and TL-BS parameters among RMDs (F(1,326) = 6.11 – 6.23, p < .02, ηp2 = .018 – .019) ); although the effect for Mean TL-BSAWAY (F(1,326) = 2.95, p = .09, ηp2 = .009) shifted to just over the critical p value.

Controlling for General Reaction Time Variability.Although limited in size, using the 12 neutral trials has some important virtues. First, the practice block has the unique quality of not being influenced by preceding emotional trails – which have been shown in some past work to result in carry-over and related inter-trial effects (Etkin, Egner, & Kalisch, 2011; Kennedy & Most, 2012; McKenna & Sharma, 2004). Second, despite the limited number of trials, the mean RT for the 12 neutral trials is strongly correlated with the RT of the full task (r = .70, p<.001), and variability of these trials is also significantly correlated (r =.38, p<.001). The mean RT of neutral trials is also significantly elevated in RMDs relative to NDCs (t(409)=2.59, p.01). This suggests that although short in length, this block is a psychometrically reasonable sample of RT varianceamong RMDs and NDCs that is, by methodological definition, not emotionally sourced.

References

Etkin, A., Egner, T., & Kalisch, R. (2011). Emotional processing in anterior cingulate and medial prefrontal cortex. Trends in Cognitive Sciences, 15(2), 85-93.

Kennedy, B. L., & Most, S. B. (2012). Perceptual, not memorial, disruption underlies emotion-induced blindness. Emotion, 12(2), 199.

Lundqvist, D., Flykt, A., & Ohman, A. (1998). Karolinska Directed Emotional Faces (Database of Standardized Facial Images).Psychology Section, Department of Clinical Neuroscience, Karolinska Hospital.

McKenna, F. P., & Sharma, D. (2004). Reversing the emotional stroop effect reveals that it is not what it seems: The role of fast and slow components. Journal of Experimental Psychology: Learning, Memory, and Cognition, 30(2), 382.