Covariation bias and its physiological correlates in panic disorder patients

A covariation bias, i.e., the overestimation of random contingencies between fear-relevant stimuli and aversive consequences, seems to characterize anxiety disorders. Panic patients (n=30) and healthy controls (n=25) were exposed to panic-relevant, neutral, and phobia-relevant but panic-irrelevant picture stimuli, followed randomly be aversive consequences (acoustic startle stimuli). While covariation estimates reflected objective contingencies in both groups, only panic patients revealed a more negative Contingent Negative Variation (CNV) to panic-relevant than to phobia-relevant and neutral pictures. For startle reflex, only main effects of picture category were found, indicating that valence effects of picture stimuli were not specifically distorted in panic patients. CNV presumably reflects a biased processing of disorder-relevant stimuli by panic patients, perhaps with the expectation that aversive consequences will follow these stimuli.     

Memory bias for panic-related material in patients with panic disorder.

Two experiments investigated memory bias for panic-related material in 40 patients with panic disorder and 40 healthy control subjects. No memory bias was found on a memory task that tested intentional encoding and explicit recall of panic-related versus non-panic-related sentences. In contrast, a significant memory bias was apparent on a memory task requiring classification of panic-related and non-panic-related words to test conceptual information processing in implicit memory. Panic patients learned panic-related material better than controls.     

Information processing biases in spider phobia: application of the Stroop and "White Noise" Paradigm

The present study examines attentional and implicit memory biases in spider phobic and nonphobic participants. The results showed that spider phobics demonstrated increased interference for neutral, negative, and spider-relevant words on a computerized Stroop task. However, no group differences emerged when adjusting for differences in color-naming speed. Prior exposure to a dead spider did result in higher overall Stroop interference in spider phobics and this appeared to be mostly pronounced for spider-relevant words. Implicit memory bias for threat was examined with a noise judgment task. Participants first heard neutral and spider-relevant sentences and implicit memory for these sentences was evaluated by having participants rate the volume of noise accompanying the presentation of old sentences intermixed with new sentences. An implicit memory bias is indicated if participants rate noise accompanying old sentences as less loud than noise accompanying new sentences. No evidence was found for an implicit memory bias in spider phobics. These findings are discussed in relation to the role of information processing biases in spider phobia.     

Attentional and memory bias for emotional information in crime victims with acute posttraumatic stress disorder (PTSD)

A combined emotional Stroop, implicit memory (tachistoscopic identification) and explicit memory (free recall) task with three types of words (trauma-related, positive, and neutral) and two exposure conditions (subliminal and supraliminal) was administered to 39 crime victims with acute posttraumatic stress disorder (PTSD) and 39 age- and sex-matched controls. PTSD subjects showed supraliminal Stroop interference for trauma-related words and a similar effect on positive words. A specific explicit memory bias was found for trauma-related words among the PTSD subjects, but no preattentive bias on the subliminally presented words, nor any implicit memory bias. Findings suggest that acute PTSD subjects have an attentional and memory bias for threat-related material. Methodological limitations of the study are reviewed, and it is proposed that further studies are needed in order to elucidate whether acute PTSD Ss display a preattentive and implicit memory bias for trauma-related material.     

Attention bias in children of patients with panic disorder

Cognitive models of panic disorder have emphasized the role of cognitive distortions in the maintenance of this disorder. Several studies have produced results consistent with this hypothesis, but it is still unclear whether cognitive biases precede anxiety disorders or whether they are a consequence of the disorder. In the present study, we compared children of individuals with panic disorder, children of individuals with animal phobia, and children of normal controls with respect to attentional bias with an emotional Stroop task, which included three types of words: panic-relevant, animal phobia-relevant, and neutral words. Our results revealed that children of panic patients did not show an attentional bias for panic-relevant stimuli. Results will be discussed in the context of theoretical models explaining the etiological factor of cognitive biases for the development of anxiety disorders.     

Memory bias for health-related information in somatoform disorders

OBJECTIVE: Cognitive processes are considered to be relevant to the etiology and maintenance of somatoform disorders (SFDs). The aim of this study was to assess explicit and implicit information-processing bias for disorder-congruent information in SFDs. METHODS: A clinical sample of 33 patients suffering from multiple somatoform symptoms (SSI-3/5) and 25 healthy controls performed an encoding task with computer-presented word lists (illness related, negative, positive, neutral content), subsequently followed by explicit memory tests (free recall and recognition) and an implicit test (word-stem completion). RESULTS: The somatoform group showed a memory bias for illness-related stimuli in the word-stem completion task, whereas the two groups did not differ in explicit memory tests. This effect could not be explained by comorbid depression. CONCLUSION: These results provide some support for current theories on SFDs.     

Implicit gambling attitudes in problem gamblers: Positive but not negative implicit associations

BACKGROUND AND OBJECTIVES: Implicit attitudes (associations) are involved in the generation of substance use behaviors. However, little is known about the role of this automatic cognitive processing in deregulated behaviors without substance use, such as abnormal gambling. This study examined whether problem gamblers exhibit both positive and negative implicit attitudes toward gambling-related stimuli. METHODS: Twenty-five problem gamblers and 25 control participants performed two unipolar (pleasant; unpleasant) Single-Target Implicit Association Tasks (unipolar ST-IAT), in which gambling pictures were associated with either pleasant (or unpleasant for the negative unipolar ST-IAT) or neutral words. Explicit attitudes toward gambling were also recorded. RESULTS: We found in problem gamblers: (i) both positive implicit and explicit attitudes toward gambling; (ii) no negative implicit gambling association; (iii) that only positive explicit attitudes positively correlated with the gambling severity score. LIMITATIONS: (i) the use of only one type of reaction time task; (ii) the use of both words and pictures in a same IAT; (iii) problem gamblers have been compared to non-gamblers instead of being contrasted with healthy non-problem gamblers. CONCLUSIONS: Whereas our gamblers experienced deleterious effects related to gambling, implicit attitude toward gambling remained positive, thus hampering attempts to quit gambling. Possible clinical interventions targeting implicit cognition in problem gamblers were discussed.     

Attentional and memory bias in persecutory delusions and depression

BACKGROUND: Previous research has indicated that persecutory delusions and depression may share similar cognitive biases at implicit levels of processing, but differentiate at explicit levels, supporting the theory that paranoia may have a protective function against underlying negative schemata. The study aimed to investigate attentional bias and both implicit and explicit memory biases for personally salient and standardised emotional stimuli in persecutory delusions and depression. SAMPLING: 36 participants, with 12 in each group, were interviewed in order to generate personally salient stimuli to be employed within the cognitive tests. Standardised emotional stimuli were additionally employed as a control. Participants completed two probe detection tasks, one including personally salient stimuli and one including standard emotional stimuli. Memory for the stimuli presented in this task was assessed by a free recall task (explicit memory) followed by a word completion task (implicit memory). RESULTS: On an implicit memory task, both the deluded and depressed groups displayed comparable retrieval of positive and negative words. However, on the explicit memory task, the depressed group demonstrated a bias for negative stimuli, whereas the deluded group demonstrated a bias for positive stimuli. The groups did not demonstrate an attentional bias for personally salient information. However, an attentional bias for standardised emotional stimuli was found in the depressed group, although this was not specific to either negative or positive stimuli. CONCLUSION: The results indicate that depression and persecutory delusions may share similar patterns of processing at an implicit level but differentiate at the explicit level, which may be indicative of cognitive avoidance of threatening stimuli in psychosis. However, this does not seem to be a feature of automatic attentional processes in people with persecutory delusions. Implications for further research are discussed.     

Variation in the corticotropin-releasing hormone receptor 1 (CRHR1) gene influences fMRI signal responses during emotional stimulus processing

The corticotropin-releasing hormone (CRH) system coordinates neuroendocrine and behavioral responses to stress and has been implicated in the development of major depressive disorder (MDD). Recent reports suggest that GG-homozygous individuals of a single nucleotide polymorphism (rs110402) in the CRH receptor 1 (CRHR1) gene show behavioral and neuroendocrine evidence of stress vulnerability. The present study explores whether those observations extend to the neuronal processing of emotional stimuli in humans. CRHR1 was genotyped in 83 controls and a preliminary sample of 16 unmedicated patients with MDD who completed a functional magnetic resonance imaging scan while viewing blocks of positive, negative, and neutral words. In addition, potential mediating factors such as early life stress, sex, personality traits, and negative memory bias were examined. Robust differences in blood oxygenation level-dependent (BOLD) signal were found in healthy controls (A allele carriers > GG-homozygotes) in the right middle temporal/angular gyrus while subjects were viewing negative versus neutral words. Among GG-homozygotes, BOLD signal in the subgenual cingulate was greater in MDD participants (n = 9) compared with controls (n = 33). Conversely, among A-carriers, BOLD signal was smaller in MDD (n = 7) compared with controls (n = 50) in the hypothalamus, bilateral amygdala, and left nucleus accumbens. Early life stress, personality traits, and levels of negative memory bias were associated with brain activity depending on genotype. Results from healthy controls and a preliminary sample of MDD participants show that CRHR1 single nucleotide polymorphism rs110402 moderates neural responses to emotional stimuli, suggesting a potential mechanism of vulnerability for the development of MDD.     

Memory bias for health-related information in somatoform disorders

ObjectiveCognitive processes are considered to be relevant to the etiology and maintenance of somatoform disorders (SFDs). The aim of this study was to assess explicit and implicit information-processing bias for disorder-congruent information in SFDs.MethodsA clinical sample of 33 patients suffering from multiple somatoform symptoms (SSI-3/5) and 25 healthy controls performed an encoding task with computer-presented word lists (illness related, negative, positive, neutral content), subsequently followed by explicit memory tests (free recall and recognition) and an implicit test (word-stem completion).ResultsThe somatoform group showed a memory bias for illness-related stimuli in the word-stem completion task, whereas the two groups did not differ in explicit memory tests. This effect could not be explained by comorbid depression.ConclusionThese results provide some support for current theories on SFDs.     

Selective memory and memory deficits in depressed inpatients

We investigated memory impairment and mood-congruent memory bias in depression, using an explicit memory test and an implicit one. Thirty-six severely depressed inpatients that fulfilled DSM-IV criteria for major depressive disorder and 36 healthy controls matched for sex, age, and educational level participated in the study. Explicit memory was assessed with a free recall task and implicit memory with an anagram solution task. Results showed that depressed and controls differed in explicit memory performance, depending on the amount of cognitive distraction between incidental learning and testing. Implicit memory was not affected. In addition, severely depressed patients showed a mood-congruent memory bias in implicit memory but not in explicit memory. The complex pattern of results is discussed with regard to relevant theories of depression.     

Brain regions showing increased activation by threat-related words in panic disorder

Threat-related stimuli consistently activate the posterior cingulate cortex in normal subjects and have exaggerated effects on memory in patients with panic disorder. We hypothesized that panic patients would show increased response to threat-related stimuli in the posterior cingulate cortex. While undergoing fMRI, six panic patients and eight healthy volunteers made valence judgements of threat-related and neutral words. Both groups showed threat-related activation in the left posterior cingulate and left middle frontal cortices, but the activation was significantly greater in panic patients. Panic patients also had more right>left asymmetry of activation in the mid-parahippocampal region. The increased responsivity observed in the posterior cingulate and dorsolateral prefrontal cortices is consistent with the hypothesis that panic disorder patients engage in more extensive memory processing of threat-related stimuli.     

A priori expectancy bias in patients with panic disorder

BACKGROUND: Several studies have indicated that phobic participants tend to overassociate fear-relevant stimuli and aversive outcomes, i.e, they show a covariation bias. Such a bias seems to be a powerful way to confirm danger expectations and enhance fear. Therefore, a covariation bias might be an important factor in the maintenance of fear. METHODS: To investigate a covariation bias in patients with panic disorder, we had 29 patients and 29 healthy control participants rate the a priori probabilities with which they would expect pictures of mushrooms, spiders, erotic scenes, and emergency situations to be paired with a tone, shock, or nothing. RESULTS: This is the first study to show that patients with panic disorder specifically overestimate the association between panic-relevant stimuli and a following negative consequence. This distorted contingency expectancy represents a panic-specific covariation bias, since it was not observable for other stimuli-consequence combinations and only to a significantly lesser degree in control participants. CONCLUSIONS: The underpinning hypothesis is that overestimation of threat plays a casual role in the origins and maintenance of anxiety. Thus anxiety may induce a covariation bias, which in turn may enhance the perceived threat, which in turn may intensify the anxiety etc. This reciprocal relationship between covariation bias and anxiety may have clinical implications for prediction and treatment in patients with panic disorder.     

Neural correlates of emotional working memory in patients with mild cognitive impairment

Emotional stimuli can have beneficial effects on memory in healthy aged subjects and partly on patients with dementia. So far, no experimental study has explored the effects of memory for emotional stimuli in patients with mild cognitive impairment (MCI), a concept that describes a transitional state between normal aging and dementia. The present fMRI study explored working memory for emotional stimuli in 16 patients with amnestic MCI (aMCI) and 16 healthy aged participants. Subjects performed an n-back task (2-back) with neutral, positive, and negative emotional pictures. The analysis focused on target processing. Results showed that groups did not differ in working memory performance. In healthy aged participants emotional targets had no significant impact on working memory. In patients with aMCI a negativity bias was observed, indicating that negative targets were better remembered compared to neutral and positive targets. Regarding fMRI results, both groups showed an increase in functional activity in prefrontal and lateral parietal brain regions associated with target processing. As a key result, we observed significant group by emotion interaction effects in the precuneus. Healthy aged participants showed a signal decrease in the left precuneus for positive compared to neutral targets. The precuneus deactivation in healthy aged participants may indicate a disengagement of self-referential processes towards task-related processes. Patients with aMCI revealed a signal increase in the right precuneus for negative compared to neutral targets. This increase in precuneus activity, combined with a behavioural facilitation effect, may indicate a mechanism to compensate disease related processes in aMCI.     

Do dissociations between implicit and explicit memory disappear, when reliability of the tests is comparable? An example

Implicit memory measures tend to be less reliable than explicit memory measures. Consequently dissociations can arise as a consequence of differential reliabilities of the tasks. In the present study the effect of a manipulation of levels of processing in an implicit and an explicit memory task were investigated in a sample of 200 students after establishing comparable reliabilities of the memory tasks. A fragmented object-naming test was used as an indirect test and a recognition task was used as a direct test. The reliabilities of these measures were comparable in all conditions. A main effect of levels of processing, but no interaction between type of test and levels of processing, was found. These findings reinforce the necessity of taking into account the reliability of memory measures for the interpretation of dissociations between explicit and implicit memory.     

A dissociation between implicit and explicit verbal memory in left temporal lobe epilepsy

PURPOSE: Temporal lobe epilepsy patients are well known to present deficits on explicit verbal memory procedures (e.g., recall, recognition). The integrity of implicit memory procedures in these patients is not established. Previous studies in this area used implicit memory measures contaminated by the effects of explicit memory. METHODS: We examined the integrity of verbal implicit and explicit memory in left temporal lobe epilepsy (LTLE) patients and hypothesized that a clear dissociation in performance would be found with a relative preservation of implicit memory. TLE patients (n = 15) and age- and education-matched healthy normal patients (n = 15) were shown a 40-word study list, followed by a test phase requiring completion of word stems based on the study words or new/unseen words. Experimental conditions involved instructions to provide either the old (study) words or novel/nonlist words when completing the stem. Measures of automaticity and recollection provided uncontaminated indices of implicit and explicit memory, respectively. RESULTS: The data showed a significant difference (p < 0.001) between the patients (Recollection, 0.12; SD, 0.18) and controls (0.50, SD, 0.15) on the measure of explicit memory. In contrast, the patients (Automaticity, 0.51; SD, 0.11) and controls (0.45, SD, 0.18) performed similarly on the implicit memory measure, with patient scores clearly at normative levels based on other Process Dissociation Procedure data. CONCLUSIONS: The data demonstrate the integrity of implicit memory in LTLE patients. Finding a dissociation between the two forms of verbal memory in LTLE patients provides evidence that they rely on different neuroanatomic systems.     

Is panic disorder linked to cognitive avoidance of threatening information?

We used a directed-forgetting paradigm to investigate whether panic disorder patients cognitively avoid threatening information. To determine if hemispheric laterality predicts processing biases in this paradigm, we used dichotic listening methods to ascertain participants' auditory perceptual asymmetry (PA). Panic disorder patients and healthy control participants viewed a series of intermixed threat, positive, and neutral words, each followed by an instruction to either remember the word or forget it. They then performed free recall and recognition tests for all words, irrespective of initial instructions. Directed-forgetting effects occurred equally for all word types: both groups recalled remember-words better than forget-words. Because this task is strongly affected by encoding style, panic patients as a group do not seem to avoid encoding threat cues. However, PA analyses revealed that cognitive avoidance of threat forget-words was significantly associated with greater left hemisphere bias in the control group and nonsignificantly associated with lesser left hemisphere bias in the panic disorder group.     

The effects of case mixing on word recognition: evidence from a PET study

The early stages of visual word recognition were investigated by scanning participants using PET as they took part in implicit and explicit reading tasks with visually disrupted stimuli. CaSe MiXiNg has been shown in behavioral studies to increase reaction times (RTs) in naming and other word recognition tasks. In this study, we found that during both an implicit (feature detection) task and an explicit word-naming task, mixed-case words compared to same-case words produced increased activation in an area of the right parietal cortex previously associated with visual attention. No effect of case was found in this area for pseudowords or consonant strings. Further, lowering the contrast of the stimuli slowed RTs as much as case mixing, but did not lead to the same increase in right parietal activation. No significant effect of case mixing was observed in left-hemisphere language areas. The results suggest that reading mixed-case words requires increased attentional processing. However, later word recognition processes may be relatively unaffected by the disruption in presentation.     

Memory for trauma-related information in Holocaust survivors with PTSD

The impact of trauma-related information on memory performance in aging Holocaust survivors with post-traumatic stress disorder (PTSD) was evaluated. Explicit and implicit memory for neutral and Holocaust-related words was assessed in Holocaust survivors with PTSD (PTSD+, n=31), in Holocaust survivors without PTSD (PTSD-, n=17), and in healthy Jewish adults not exposed to the Holocaust (non-exposed, n=34) using the paired associates learning and word-stem completion tests, respectively. The PTSD+ group had significantly poorer paired associate recall than the PTSD- and non-exposed groups, and showed a significantly different response to the introduction of Holocaust-related words. The PTSD+ group recalled significantly more words from the Holocaust-related than the neutral word pairs, whereas word type had little effect on paired associate recall in the other two groups. In contrast, there were no group differences in implicit memory performance or in the effect of Holocaust-related words on implicit memory. Among Holocaust survivors, explicit recall of Holocaust-related word pairs was associated with intrusive PTSD symptoms. These results suggest that aging Holocaust survivors with PTSD preferentially form new associations with trauma-related stimuli as compared with neutral stimuli. The presence of such a disturbance of associative learning decades after the Holocaust may underlie the persistence of psychological symptoms and, in particular, the intrusive symptoms of PTSD. This trauma-related facilitation of explicit memory, together with generally poorer explicit memory, may help to explain the bi-directional nature of the memory impairments in PTSD.     

Implicit self-esteem in bulimia nervosa

Implicit and explicit self-esteem were compared in a group of female participants with bulimia nervosa or binge eating disorder (n = 20) and a healthy control group (n = 20). Lower explicit and a less positive implicit self-esteem bias in the clinical group was predicted. Participants completed a self-esteem implicit association test and two explicit self-esteem measures. The eating disordered group had lower explicit self-esteem, but a more positive implicit self-esteem bias than controls. The results are discussed in relation to the idea that discrepancies between implicit and explicit self-esteem reflect fragile self-esteem and are related to high levels of perfectionism, which is associated with eating disorders.