Péter Pajkossy

Impaired executive functions in subjects with frequent nightmares as reflected by performance in different neuropsychological tasks

Nightmare disorder is a prevalent parasomnia characterized by vivid and highly unpleasant dream experiences during night time sleep. The neural background of disturbed dreaming was proposed to be associated with impaired prefrontal and fronto-limbic functioning during REM sleep. We hypothesized that the impaired prefrontal and fronto-limbic functioning in subjects with frequent nightmares would be reflected at the behavioral level during waking tasks as well. 35-35 Subjects with frequent nightmares and matched controls participated in Study 1, involving an Emotional Go/NoGo, an Emotional Stroop task, and a Verbal Fluency task. Nightmare subjects exhibited longer reaction times in the Emotional Go/NoGo and Emotional Stroop tasks. Moreover, they committed more perseveration errors and showed less fluent word generation in the Verbal Fluency task. Nightmare subjects showed an overall slowing irrespective of the valence of the stimuli. While the effects of sleep quality and waking anxiety were associated to these deficits in some cases, these factors could not solely explain the difference between the two groups. In Study 2, 17 subjects with frequent nightmares and 18 controls were compared by a Color-word and an Emotional, block design Stroop task in order to avoid the slow effects of emotional interference potentially caused by previous items. Nightmare subjects were characterized by an overall slowing in the Emotional Stroop task, irrespective of the valence of the stimuli. In the Color-word Stroop task, nightmare subjects were not significantly slower in comparison with controls. Our results suggest that individuals with frequent nightmares are impaired in executive tasks involving the suppression of task-irrelevant semantic representations.

The opposite effect of trait and state anxiety on Iowa Gambling Task

Abstract The impact of state/trait anxiety and worry on decision-making was investigated applying a computerized gambling task (Iowa Gambling Task). Besides, using two measures of knowledge about the task-contingencies, we examined the role of declarative knowledge in successful performance on the task and we tested whether the amount of declarative knowledge is related to anxiety. Results showed that trait anxiety has a negative impact, while state anxiety and worry have a positive impact on performance on the Iowa Gambling Task. Furthermore, responses on post-experiment survey suggest that those who perform better on the Iowa Gambling Task are more likely to form and report correct declarative knowledge about the task-rules. This ability, however, was not associated with anxiety.

Tonic noradrenergic activity modulates explorative behavior and attentional set shifting: Evidence from pupillometry and gaze pattern analysis

A constant task for every living organism is to decide whether to exploit rewards associated with current behavior or to explore the environment for more rewarding options. Current empirical evidence indicates that exploitation is related to phasic whereas exploration is related to tonic firing mode of noradrenergic neurons in the locus coeruleus. In humans, this exploration-exploitation trade-off is subserved by the ability to flexibly switch attention between task-related and task-irrelevant information. Here, we investigated whether this function, called attentional set shifting, is related to exploration and tonic noradrenergic discharge. We measured pretrial baseline pupil dilation, proved to be strongly correlated with the activity of the locus coeruleus, while human participants took part in well-known tasks of attentional set shifting. Study 1 used the Wisconsin Card Sorting Task, whereas in Study 2, the Intra/Extradimensional Set Shifting Task was used. Both tasks require participants to choose between different compound stimuli based on feedback provided for their previous decisions. During the task, stimulus-reward contingencies change periodically, thus participants are repeatedly required to reassess which stimulus features are relevant (i.e., they shift their attentional set). Our results showed that baseline pupil diameter steadily decreased when the stimulus-reward contingencies were stable, whereas they suddenly increased when these contingencies changed. Analysis of looking patterns also confirmed the presence of exploratory behavior during attentional set shifting. Thus, our results suggest that tonic firing mode of noradrenergic neurons in the locus coeruleus is implicated in attentional set shifting, as it regulates the amount of exploration.

Mirroring intentional forgetting in a shared-goal learning situation.

Background Intentional forgetting refers to the surprising phenomenon that we can forget previously successfully encoded memories if we are instructed to do so. Here, we show that participants cannot only intentionally forget episodic memories but they can also mirror the “forgetting performance” of an observed model. Methodology/Principal Findings In four experiments a participant observed a model who took part in a memory experiment. In Experiment 1 and 2 observers saw a movie about the experiment, whereas in Experiment 3 and 4 the observers and the models took part together in a real laboratory experiment. The observed memory experiment was a directed forgetting experiment where the models learned two lists of items and were instructed either to forget or to remember the first list. In Experiment 1 and 3 observers were instructed to simply observe the experiment (“simple observation” instruction). In Experiment 2 and 4, observers received instructions aimed to induce the same learning goal for the observers and the models (“observation with goal-sharing” instruction). A directed forgetting effect (the reliably lower recall of to-be-forgotten items) emerged only when models received the “observation with goal-sharing” instruction (P<.001 in Experiment 2, and P<.05 in Experiment 4), and it was absent when observers received the “simple observation” instruction (P>.1 in Experiment 1 and 3). Conclusion If people observe another person with the same intention to learn, and see that this person is instructed to forget previously studied information, then they will produce the same intentional forgetting effect as the person they observed. This seems to be a an important aspect of human learning: if we can understand the goal of an observed person and this is in line with our behavioural goals then our learning performance will mirror the learning performance of the model.

Erratum to “Impaired executive functions in subjects with frequent nightmares as reflected by performance in different neuropsychological tasks” [Brain Cognit. 78 (2012) 274–283]

In the above mentioned paper, in Section 2.2.4 the results read: The between subject Group had a significant main effect on Perseveration scores (F1,68 = 11.47, p < 0.001) because of the significantly higher scores of perseveration errors in the NM (M = 0.4 ± 0.32) compared with the CTL group (M = 0.18 ± 0.23). The correct text is in Section 2.2.4 the results read: The between subject Group had a significant main effect on Perseveration scores (F1,68 = 11.47, p < 0.001) because of the significantly higher scores of perseveration errors in the NM (M = 0.04 ± 0.032) compared with the CTL group (M = 0.018 ± 0.023).

Acute stress affects prospective memory functions via associative memory processes

Recent findings suggest that acute stress can improve the execution of delayed intentions (prospective memory, PM). However, it is unclear whether this improvement can be explained by altered executive control processes or by altered associative memory functioning. To investigate this issue, we used physical-psychosocial stressors to induce acute stress in laboratory settings. Then participants completed event- and time-based PM tasks requiring the different contribution of control processes and a control task (letter fluency) frequently used to measure executive functions. According to our results, acute stress had no impact on ongoing task performance, time-based PM, and verbal fluency, whereas it enhanced event-based PM as measured by response speed for the prospective cues. Our findings indicate that, here, acute stress did not affect executive control processes. We suggest that stress affected event-based PM via associative memory processes.

The interplay of trait worry and trait anxiety in determining episodic retrieval: The role of cognitive control

Worrying is a key concept in describing the complex relationship between anxiety and cognitive control. On the one hand, cognitive control processes might underlie the specific tendency to engage in worrying (i.e., trait worry), conceptualized as a future-oriented mental problem-solving activity. On the other hand, the general tendency to experience the signs and symptoms of anxiety (i.e., trait anxiety) is suggested to impair cognitive control because worrisome thoughts interfere with task-relevant processing. Based on these opposing tendencies, we predicted that the effect of the two related constructs, trait anxiety and trait worry, might cancel out one another. In statistics, such instances have been termed suppressor situations. In four experiments, we found evidence for such a suppressor situation: When their shared variance was controlled, trait worry was positively whereas trait anxiety was negatively related to performance in a memory task requiring strategic, effortful retrieval. We also showed that these opposing effects are related to temporal context reinstatement. Our results suggest that trait worry and trait anxiety possess unique sources of variance, which differently relate to performance in memory tasks requiring cognitive control.

Hypnosis Attenuates Executive Cost of Prospective Memory

Abstract Prospective memory is the ability to formulate and carry out actions at the appropriate time or in the appropriate context. This study aimed to identify the effect of hypnosis on prospective memory performance and to analyze the involvement of executive control processes in intention realization in a hypnotically altered state of consciousness. In 1 experiment, manipulating hypnotic instruction in a within-subject fashion, the authors explored the event-based prospective memory performance of 23 volunteers in 3 conditions: baseline, expectation, and execution. The primary result was that executing prospective memory responses, at the same accuracy rate, produced a significantly lower cost of ongoing responses in terms of response latency in the hypnotic state than in wake condition.

Visuo-spatial memory impairment in obsessive compulsive disorder (OCD): from neuropsychological findings to eye-tracking

abstract There is a growing amount of evidence about the deficit of executive system in OCD, which is strongly related to the fronto-basal loop dysfunctions of the disorder (e.g. Chamberlain et al., 2005; Olley et al., 2007). In addition to the executive deficit, several studies found impaired visual and spatial memory performance in this disorder. In an early neuropsychological model, Savage (1998) suggested that the fronto-striatal dysfunctions along with impaired executive functioning leads to observed memory difficulties (encoding and retrieval of nonverbal information). Following this suggestion, here we aimed at investigating visuo-spatial memory functions in a pool of OCD patients in two studies. We combined neuropsychological tasks and computer based working memory paradigms with eye-tracking methodology. In Study 1 the Rey Complex Figure Task (RCFT) was used and it was found that OCD patients performed significantly poorer in the copy and recall phase of the task in comparison with matched healthy control group. Symptom severity and the level of anxiety were assessed by the Yale Brown Obsessive Compulsive Scale (Y-BOCS) and the State-Trait Anxiety Inventory (STAI), respectively. There was a significant negative correlation between symptom severity (Y-BOCS total scores) and the recall scores of the RCFT. In Study 2 we developed a computer-based Visual Pattern Task to investigate the eye movement correlates of cognitive processes involved in visuo-spatial working memory function. In addition subjects were also screened by a neuropsychological test battery including tasks on shifting (Wisconsin Card Sorting Test), response inhibition (Stop Signal Task, Stroop Task) and working memory capacity functions (n-back Task). According to our preliminary eye-tracking results, in comparison with healthy control subjects, OCD patients produced a significant decrease in target-related dwell time scores during the delay phase of the task. We will discuss the possible relationships between eye movement patterns, cognitive deficits and symptom severity.

The probability of association between response inhibition and compulsive symptoms of obsessive-compulsive disorder: response to Abramovitch and Abramowitz.

Abramovitch and Abramowitz (2014) listed several problems with the conclusions they interpret as having been drawn from cross-sectional (correlational) data in our recent article (Harsányi et al., 2014). First of all, causal inferences such as response inhibition deficits underlying compulsive rituals cannot logically be concluded from correlational data. However, this conclusion was never drawn in our article. Contrary to what Abramovitch and Abramowitz state in their Letter to the Editors, we did not conclude that response inhibition leads to obsessive-compulsive disorder (OCD); rather, we reported that inhibition deficit can be observed in OCD. We, of course, share the opinion of Abramovitch and Abramowitz that extensive deficits of executive functions, including response inhibition, are identifiable in several other psychiatric illnesses (e.g., in schizophrenia, bipolar affective disorder, attention deficit/hyperactivity disorder, anxiety disorders, and depression). We described correlations in our article based on the results of our research. However, we would like to emphasize the fact that in the case of the 51 OCD patients, we not only used questionnaires measuring executive functions (DEX, WBSI), but we also used a well-validated neurocognitive test battery to assess these functions. Abramovitch and Abramowitz question whether the Dysexecutive Questionnaire (DEX) adequately measures executive deficits. They base their skepticism on a study by Chaytor et al. (2006) in which the correlation of the DEX with executive tests was not particularly high. In reference, we would like to highlight that the study by Chaytor et al. (2006) is grounded on the data of a group of merely 46 patients, with a variety of neurological disorders, where correlation was carried out with a few tests measuring executive performance and experimental methods (Wisconsin Card Sorting Test (WCST), Trail Making Test, Stroop Color and Word Test, Controlled Oral Word Association Test (COWAT)), and between the DEX and other questionnaires. This study found a moderate correlation between the DEX and the Stroop task (r1⁄40.35) and weak or no correlation between the DEX and the Trail Making Test-Part B, COWAT and WCST (r1⁄40.25, r1⁄40.28, r1⁄40.03, respectively). In our opinion, the biggest problemwith this study is that it did not find a substantially stronger correlation between the other executive tests either. For example, the WCST shows an r1⁄40.34 correlation with the Trail Making Test-Part B, and an r1⁄40.33 and r1⁄40.00 correlation with the Stroop interference scores. Does this mean that the WCTS is also an inadequate tool for measuring executive deficit? Wilson et al. (1996) and Burgess et al. (1998), in contrast with Chaytor et al. (2006), when standardizing the DEX, examined 92 patients with brain injuries (closed head injuries, encephalitis, dementia, stroke) and compared data from the DEX with one of the most comprehensive neuropsychological test batteries (Behavioral Assessment of the Dysexecutive Syndrome (BADS)), consisting of six sub-tests. Research data showed a strong correlation between the BADS total score and DEX other ratings (r1⁄4 0.62). The above-cited studies indicate that we can, indeed, regard the DEX score of significant other ratings as a reliable research tool. Since the manual of the DEX/BADS presents inclusive statistics of dysexecutive symptoms of frontal lobe brain injury patients, the sentence in our publication, namely that ‘Based on the normative scales of the DEX questionnaire the presence and severity of executive problems of our 51 OCD patients were between 31 and 53 percentile, which shows a severe executive impairment comparing to the normal control of the manual of the DEX,’ needs to be more accurate. In the DEX/BADS manual, the percentage values are not representative of normal persons but of brain injury patients. Therefore, the fact that the executive function disorders in our examined OCD patients fell between 25 and 50 percent provides an even stronger basis for the presence of ‘severe executive impairment’, as it stands on a comparable level with the ‘severe’ extent of injury level reflecting executive deficit in brain injury patients. However, we did make an ambiguous statement in our article, but owing to the standardization logic of the DEX, the 25– 50 percent value in our examined OCD group (based on the data of a group of patients with brain injuries showing severe executive deficit) qualifies in the severely impaired range. Nonetheless, we can also assert, based on clinical data of our examined sample of patients, that DEX values correlated well with inhibition markers in the conducted executive tests measuring attentional focus and switching skills. To summarize, in our opinion, it is far from clear that the DEX is an unreliable neuropsychological tool, based both on literature and our own data. The neuropsychological tasks used to examine executive functions in our research confirm that scores of the DEX other ratings are capable of describing executive deficit and provide an ecologically valid measurement. Regarding OCD and impulsivity, on the one hand, we are of a similar opinion as Abramovitch and Abramowitz in that compulsions are ‘carefully planned and executed, and are usually carefully timed in response to obsessions.’ At the same time, we disagree with their assertion based on clinical observations that ‘...in clinical work with patients, it is easy to observe that individuals