Single-trial log transformation is optimal in frequency analysis of resting EEG alpha.

The appropriate definition and scaling of the magnitude of electroencephalogram (EEG) oscillations is an underdeveloped area. The aim of this study was to optimize the analysis of resting EEG alpha magnitude, focusing on alpha peak frequency and nonlinear transformation of alpha power. A family of nonlinear transforms, Box-Cox transforms, were applied to find the transform that (a) maximized a non-disputed effect: the increase in alpha magnitude when the eyes are closed (Berger effect), and (b) made the distribution of alpha magnitude closest to normal across epochs within each participant, or across participants. The transformations were performed either at the single epoch level or at the epoch-average level. Alpha peak frequency showed large individual differences, yet good correspondence between various ways to estimate it in 2 min of eyes-closed and 2 min of eyes-open resting EEG data. Both alpha magnitude and the Berger effect were larger for individual alpha than for a generic (8-12 Hz) alpha band. The log-transform on single epochs (a) maximized the t-value of the contrast between the eyes-open and eyes-closed conditions when tested within each participant, and (b) rendered near-normally distributed alpha power across epochs and participants, thereby making further transformation of epoch averages superfluous. The results suggest that the log-normal distribution is a fundamental property of variations in alpha power across time in the order of seconds. Moreover, effects on alpha power appear to be multiplicative rather than additive. These findings support the use of the log-transform on single epochs to achieve appropriate scaling of alpha magnitude.

Cue exposure therapy reduces overeating of exposed and non-exposed foods in obese adolescents.

BACKGROUND AND OBJECTIVES: This study tested whether two sessions of food cue exposure therapy reduced eating in the absence of hunger (EAH), specified for exposed and non-exposed food, in overweight and obese adolescents, and whether habituation of food cue reactivity and reduced CS-US expectancies predicted a decrease in EAH. METHODS: 41 overweight adolescents (aged 12-18 years) were randomly assigned to a cue exposure intervention or a lifestyle intervention (control condition). Habituation of food cue reactivity (self-reported desire to eat and salivation) and CS-US expectancy were measured during both sessions, and EAH was measured at the end of session two. RESULTS: Compared to the control condition, the cue exposure condition showed less EAH for the exposed food item as well as for the non-exposed food items. Larger within-session (WSH) and between-session habituation (BSH) of cue reactivity were not related to less EAH, change in CS-US expectancy was unrelated to EAH. LIMITATIONS: The study was underpowered, and compliance to homework instructions between sessions was poor, intervention effects might have been larger when participants adhered to daily homework exercises. CONCLUSIONS: Food cue exposure was effective to reduce EAH of exposed and non-exposed food items, indicating generalisability of the exposure effect. In line with exposure effects in anxiety disorders, habituation was not found to benefit outcome, though the present data do also not provide evidence that CS-US expectancy violation predicts EAH.

Measuring working memory load effects on electrophysiological markers of attention orienting during a simulated drive.

Intersection accidents result in a significant proportion of road fatalities, and attention allocation likely plays a role. Attention allocation may depend on (limited) working memory (WM) capacity. Driving is often combined with tasks increasing WM load, consequently impairing attention orienting. This study (n = 22) investigated WM load effects on event-related potentials (ERPs) related to attention orienting. A simulated driving environment allowed continuous lane-keeping measurement. Participants were asked to orient attention covertly towards the side indicated by an arrow, and to respond only to moving cars appearing on the attended side by pressing a button. WM load was manipulated using a concurrent memory task. ERPs showed typical attentional modulation (cue: contralateral negativity, LDAP; car: N1, P1, SN and P3) under low and high load conditions. With increased WM load, lane-keeping performance improved, while dual task performance degraded (memory task: increased error rate; orienting task: increased false alarms, smaller P3). Practitioner Summary: Intersection driver-support systems aim to improve traffic safety and flow. However, in-vehicle systems induce WM load, increasing the tendency to yield. Traffic flow reduces if drivers stop at inappropriate times, reducing the effectiveness of systems. Consequently, driver-support systems could include WM load measurement during driving in the development phase.

Learned interval time facilitates associate memory retrieval.

The extent to which time is represented in memory remains underinvestigated. We designed a time paired associate task (TPAT) in which participants implicitly learned cue-time-target associations between cue-target pairs and specific cue-target intervals. During subsequent memory testing, participants showed increased accuracy of identifying matching cue-target pairs if the time interval during testing matched the implicitly learned interval. A control experiment showed that participants had no explicit knowledge about the cue-time associations. We suggest that "elapsed time" can act as a temporal mnemonic associate that can facilitate retrieval of events associated in memory.

Effect of working memory load on electrophysiological markers of visuospatial orienting in a spatial cueing task simulating a traffic situation.

Visuospatial attentional orienting has typically been studied in abstract tasks with low ecological validity. However, real-life tasks such as driving require allocation of working memory (WM) resources to several subtasks over and above orienting in a complex sensory environment. The aims of this study were twofold: firstly, to establish whether electrophysiological signatures of attentional orienting commonly observed under simplified task conditions generalize to a more naturalistic task situation with realistic-looking stimuli, and, secondly, to assess how these signatures are affected by increased WM load under such conditions. Sixteen healthy participants performed a dual task consisting of a spatial cueing paradigm and a concurrent verbal memory task that simulated aspects of an actual traffic situation. Behaviorally, we observed a load-induced detriment of sensitivity to targets. In the EEG, we replicated orienting-related alpha lateralization, the lateralized ERPs ADAN, EDAN, and LDAP, and the P1-N1 attention effect. When WM load was high (i.e., WM resources were reduced), lateralization of oscillatory activity in the lower alpha band was delayed. In the ERPs, we found that ADAN was also delayed, while EDAN was absent. Later ERP correlates were unaffected by load. Our results show that the findings in highly controlled artificial tasks can be generalized to spatial orienting in ecologically more valid tasks, and further suggest that the initiation of spatial orienting is delayed when WM demands of an unrelated secondary task are high.

The role of frontal EEG asymmetry in post-traumatic stress disorder.

Frontal alpha asymmetry, a biomarker derived from electroencephalography (EEG) recordings, has often been associated with psychological adjustment, with more left-sided frontal activity predicting approach motivation and lower levels of depression and anxiety. This suggests high relevance to post-traumatic stress disorder (PTSD), a disorder comprising anxiety and dysphoria symptoms. We review this relationship and show that frontal asymmetry can be plausibly linked to neuropsychological abnormalities seen in PTSD. However, surprisingly few studies (k = 8) have directly addressed frontal asymmetry in PTSD, mostly reporting that trait frontal asymmetry has little (if any) predictive value. Meanwhile, preliminary evidence suggest that state-dependent asymmetry during trauma-relevant stimulation distinguishes PTSD patients from resilient individuals. Thus, exploring links between provocation-induced EEG asymmetry and PTSD appears particularly promising. Additionally, we recommend more fine-grained analyses into PTSD symptom clusters in relation to frontal asymmetry. Finally, we highlight hypotheses that may guide future research and help to fully apprehend the practical and theoretical relevance of this biological marker.

The cognitive mechanisms underlying deception: an event-related potential study.

The cognitive view on deception proposes that lying comes with a cognitive cost. This view is supported by the finding that lying typically takes longer than truth telling. Event-related potentials (ERPs) provide a means to unravel the cognitive processes underlying this cost. Using a mock-crime design, the current study (n=20) investigated the effects of deception on the Contingent Negative Variation (CNV), the Lateralized Readiness Potential (LRP), the Correct Response Negativity (CRN), and the stimulus-locked N200 and P300 components. In line with previous research, lying resulted in more errors, longer reaction times (RTs) and longer RT standard deviations compared to truthful responses. A marginally significant effect suggested a stronger CNV for the anticipation of lying compared to the anticipation of truth telling. There were no significant deception effects on the stimulus- and the response-locked LRPs. Unexpectedly, we found a significantly larger CRN for truth telling compared to lying. Additional analyses revealed an enhanced N200 and a decreased P300 for lying compared to truth telling. Our results support the cognitive load hypothesis for lying, yet are mixed regarding the response conflict hypothesis. Results are discussed with regard to the specific characteristics of our design and their theoretical and applied implications.

Measuring automatic associations: validation of algorithms for the Implicit Association Test (IAT) in a laboratory setting.

BACKGROUND AND OBJECTIVES: In their paper, "Understanding and using the Implicit Association Test: I. An improved scoring algorithm", Greenwald, Nosek, and Banaji (2003) investigated different ways to calculate the IAT-effect. However, up to now, it remained unclear whether these findings - based on internet data - also generalize to laboratory settings. Therefore, the main goal of the present study was to cross-validate scoring algorithms for the IAT in a laboratory setting, specifically in the domain of psychopathology. METHODS: Four known IAT algorithms and seven alternative IAT algorithms were evaluated on several performance criteria in the large-scale laboratory sample of the Netherlands Study of Depression and Anxiety (N = 2981) in which two IATs were included to obtain measurements of automatic self-anxious and automatic self-depressed associations. RESULTS AND CONCLUSIONS: Results clearly demonstrated that the D(2SD)-measure and the D(600)-measure as well as an alternative algorithm based on the correct trials only (D(noEP)-measure) are suitable to be used in a laboratory setting for IATs with a fixed order of category combinations. It remains important to further replicate these findings, especially in studies that include outcome measures of more spontaneous kinds of behaviors.

Cognitive processes and attitudes in bipolar disorder: a study into personality, dysfunctional attitudes and attention bias in patients with bipolar disorder and their relatives.

BACKGROUND: Research in cognitive processes and attitudes in bipolar disorder is scarce and has provided mixed findings, possibly due to differences in current mood state. It is unclear whether alterations in cognitive processes and attitudes are only related to the depressive mood states of bipolar patients or also represent a vulnerability marker for the development of future (depressive) episodes. This was investigated in the current study. METHODS: Both implicit (attentional bias for emotional words) and explicit (dysfunctional attitudes and personality characteristics) measures of cognitive processes and attitudes were assessed in 77 bipolar patients with varying levels of depressive symptoms (depressed=17, euthymic n=60), their healthy first-degree relatives (n=39) and a healthy control group (n=61). Analyses of variance were used to investigate differences between groups. RESULTS: Mildly depressed patients with bipolar disorder demonstrated an attentional bias away from positive emotional words and showed increased dysfunctional attitudes and higher levels of neuroticism. Euthymic patients were largely comparable to healthy controls and only differed from controls in higher levels of neuroticism. Relatives were similar to controls on all measures, although they significantly differed from bipolar patients in displaying less neuroticism and more extraversion. LIMITATIONS: No firm conclusions regarding causality can be drawn from the associations that were found between cognitive processes and attitudes and the evolution of mood symptoms in bipolar disorder. CONCLUSION: Alterations in cognitive processes and attitudes in bipolar patients appear to be mostly related to the expression of mood symptomatology rather than to the vulnerability for bipolar disorder.

Implicit measures of association in psychopathology research.

Studies obtaining implicit measures of associations in Diagnostic and Statistical Manual of Mental Disorders (4th ed., Text Revision; American Psychiatric Association, 2000) Axis I psychopathology are organized into three categories: (a) studies comparing groups having a disorder with controls, (b) experimental validity studies, and (c) incremental and predictive validity studies. In the first category, implicit measures of disorder-relevant associations were consistent with explicit beliefs for some disorders (e.g., specific phobia), but for other disorders evidence was either mixed (e.g., panic disorder) or inconsistent with explicit beliefs (e.g., pain disorder). For substance use disorders and overeating, expected positive and unexpected negative associations with craved substances were found consistently. Contrary to expectation, implicit measures of self-esteem were consistently positive for patients with depressive disorder, social phobia, and body dysmorphic disorder. In the second category, short-term manipulations of disorder-relevant states generally affected implicit measures as expected. Therapeutic interventions affected implicit measures for one type of specific phobia, social phobia, and panic disorder, but not for alcohol use disorders or obesity. In the third category, implicit measures had predictive value for certain psychopathological behaviors, sometimes moderated by the availability of cognitive resources (e.g., for alcohol and food, only when cognitive resources were limited). The strengths of implicit measures include (a) converging evidence for dysfunctional beliefs regarding certain disorders and consistent new insights for other disorders and (b) prediction of some psychopathological behaviors that explicit measures cannot explain. Weaknesses include (a) that findings were inconsistent for some disorders, raising doubts about the validity of the measures, and (b) that understanding of the concept "implicit" is incomplete.

Extracting concealed information from groups.

Lie detection procedures are typically aimed at determining guilt or innocence of a single suspect. Serious security threats, however, often involve groups, such as terrorist networks or criminal organizations. In this report, we describe a variant of the skin conductance-based Concealed Information Test (CIT) that allows for the extraction of critical information from such groups. Twelve participants were given information about an upcoming (mock) terrorist attack, with specific instructions not to reveal this information to anyone. Next, each subject was subjected to a CIT, with questions pertaining to the details of the attack. Results showed that for every question, the average skin conductance response to the correct answer option differed significantly (p < 0.05) from those to all other options. These results show that the information about the upcoming attack could be extracted from the group of terror suspects as a whole.

Simplifying jackknifing of ERPs and getting more out of it: retrieving estimates of participants' latencies.

Abstract Research has demonstrated that the jackknifing procedure for estimating ERP latencies (J. Miller, T. Patterson, & R. Ulrich, 1998) yields more accurate estimates of differences between experimental conditions in ERP latency than other methods. However, the scores resulting from this procedure require special adjustments for further analyses and do not directly reflect each participant's latency. Here, a simple transform is proposed that retrieves estimates of each participant's latency from the subaverage scores, rendering further adjustments superfluous. Other advantages of working with participants' latencies are discussed. Results of simulations support the validity of jackknifing and the retrieval transform.

The contribution of mere recognition to the p300 effect in a concealed information test.

In two experiments, we investigated the role of mere recognition in a P300 based CIT. Mere recognition was isolated by having participants respond based on an irrelevant dimension of the stimuli. In Experiment 1 stimuli consisted of familiar and unfamiliar faces, with a dot placed on the left or the right cheek. Participants responded according to dot location. In the second experiment, participants were presented with autobiographical information, alternated with irrelevant stimuli, while instructed to respond based on the case of the stimuli. Results showed that with both familiar faces, and autobiographical information, mere recognition was sufficient to elicit a P300.

The effect of visual sexual content on the event-related potential.

In the present study we investigated the effect of emotional valence and arousal value of non-erotic visual stimuli on event-related potentials. We also directly compared the effects of erotic and non-erotic stimuli of comparable valence and arousal levels. Sixteen sexually functional heterosexual males rated 150 computer screen pictures, selected from the International Affective Picture System, representing five stimulus types differing along dimensions of emotional valence and arousal, and erotic vs. non-erotic content. A positive deflection of the ERP between 300 and 500 ms after stimulus onset (P300) was found to be sensitive to stimulus differences, with positive valence and high arousal resulting in larger P300. Furthermore, the positive slow wave (PSW) between 500 and 750 ms revealed additive effects of valence and arousal value. High arousal and positive valence of the stimuli resulted in larger PSW. Importantly, an interaction effect was absent here. In addition, sexual content led to a larger P300 and PSW than expected on the basis of a mere additive contribution of high arousal and positive valence.

The P300 is sensitive to concealed face recognition.

In two experiments, we investigated whether a P300 based Concealed Information Test (CIT) can be used to detect concealed face recognition. The results show that detection of concealed face recognition is highly successful when stimuli depict persons who are personally highly familiar, and instructions to conceal recognition are given. When pictures depict recognized, but personally less familiar faces, and no specific instructions to conceal recognition are given, detection is unsuccessful. These findings indicate that pictures of faces can be used in a P300 based CIT, and that mere recognition is not sufficient for successful detection of concealed information.

Lateralized ERP components related to spatial orienting: discriminating the direction of attention from processing sensory aspects of the cue.

Two spatial cueing experiments were conducted to examine the functional significance of lateralized ERP components after cue-onset and to discriminate components related to sensory cue aspects and components related to the direction of attention. In Experiment 1, a simple detection task was presented. In Experiment 2, attentional selection was augmented. Two unimodal visual cueing tasks were presented using nonlateralized line cues and lateralized arrow cues. Lateralized cue effects and modulation after stimulus onset were stronger in Experiment 2. An early posterior component was related to the physical shape of arrows. A posterior negativity (EDAN) may be related to the encoding of direction from arrow cues. An anterior negativity (ADAN) and a posterior positivity (LDAP) were related to the direction of attention. The ADAN was delayed when it was more difficult to derive cue meaning. Finally, the data suggested an overlap of the LDAP and the EDAN.

Combining skin conductance and forced choice in the detection of concealed information.

An advantage of the concealed information polygraph test (CIT) is that its false positive rate is determined on statistical grounds, and can be set a priori at arbitrary low levels (i.e., few innocents declared guilty). This criterion, however, inevitably leads to a loss of sensitivity (i.e., more guilty suspects declared innocent). We explored whether the sensitivity of a CIT procedure could be increased by adding an independent measure that is based on an entirely different psychological mechanism. In two experiments, we explored whether the accuracy of a CIT procedure could be increased by adding Symptom Validity Testing (SVT), a relatively simple, forced-choice, self-report procedure that has previously been used to detect malingering in various contexts. Results of a feigned amnesia experiment but not from a mock crime experiment showed that a combination measure of both tests yielded better detection than either test alone.

Sequence effects in a spatial cueing task: endogenous orienting is sensitive to orienting in the preceding trial.

In a spatial cueing paradigm it was investigated whether endogenous orienting is sensitive to orienting processes in the previous trial. Specifically, the effect of the previous cue direction, the previous trial type (valid, invalid, neutral, catch) and target alternation effects were studied. Strategic effects were shown as attentional costs and benefits were larger after a valid than after an invalid trial. Following catch trials, an overall response slowing was observed, but costs and benefits were unaffected. This was interpreted as a reduction in alertness and as support for the dissociation between spatial and temporal attentional mechanisms. Repetition of target position per se had no effect, but in neutral trials responses were slower to targets appearing at the location that was cued in the previous trial, independent of validity of the preceding trial. This suggests that long-term inhibition-of-return can occur between trials when attention is controlled endogenously.

Attentional bias and general orienting processes in bipolar disorder.

Attentional biases for emotional stimuli and general orienting processes were examined in bipolar disorder, using a modified dot-probe task with a spatial cueing paradigm incorporated in it. Bipolar patients in a euthymic state (i.e., remission), bipolar patients in a mildly depressed state, and non-psychiatric controls participated. General orienting results showed that within the patient group as a whole, measures of depressed mood were positively associated with a relative inability to disengage attention. Attentional bias results showed that bipolar patients in a mildly depressed state, in comparison with controls, directed their attention away from depression-related words and positive words. The bias away from positive words was equally present in both patient groups and part of a trait effect, demonstrated by the comparison of patients in a euthymic state and controls. The bias away from depression-related words was mood state-dependent and within the patient group as a whole correlated negatively with measures of depressed mood. It is proposed that biases for emotional stimuli are related to the transition of mood states, characteristic for bipolar disorder.

A Simon effect for threat-related stimulus content.

When a threat-related stimulus is preferentially processed, it may act as if it is presented alone, and thus trigger processes comparable with the effects elicited by a single stimulus. Peripheral stimuli are known to yield a Simon effect: faster responses when stimulus and response spatially correspond than when not. We designed a task during which a threat-related (physical threat, social threat, or height) word is presented with a neutral word (14 or 500 ms, masked), one above the other, and spatial correspondence of threat-related word and response varies across trials. Undergraduates performed this task when exposed to height (N=22) or in a lab (N=25). The height group, compared to the control group, showed a content-specific Simon effect for physical-threat words. This result adds evidence to the hypothesis of preferential processing of relevant threat-related information.