Stephan Walther

Neural correlates of impaired cognitive-behavioral flexibility in anorexia nervosa

OBJECTIVE Impaired cognitive-behavioral flexibility is regarded as a trait marker in anorexia nervosa patients. The authors sought to investigate the neural correlates of this deficit in executive functioning in anorexia nervosa. METHOD Fifteen women with anorexia nervosa and 15 age-matched healthy comparison women underwent event-related functional MRI while performing a target-detection task. The task distinguished between shifts in behavioral response and shifts in cognitive set. It involved infrequent target and non-target distractor stimuli embedded in a sequence of prepotent standard stimuli. RESULTS Relative to comparison subjects, anorexia nervosa patients showed a significantly higher error rate in behavioral response shifting, independent of whether those runs also involved cognitive set shifting. During behavioral response shifting, patients showed reduced activation in the left and right thalamus, ventral striatum, anterior cingulate cortex, sensorimotor brain regions, and cerebellum that differed significantly from the comparison group but showed dominant activation in frontal and parietal brain regions. These differential activations in patients and comparison subjects were specific to shifts in behavioral response: except for thalamic activation, they were not observed in response to non-target distractor trials that required no alteration in behavioral response. CONCLUSION Impaired behavioral response shifting in anorexia nervosa seems to be associated with hypoactivation in the ventral anterior cingulate-striato-thalamic loop that is involved in motivation-related behavior. In contrast, anorexia nervosa patients showed predominant activation of frontoparietal networks that is indicative of effortful and supervisory cognitive control during task performance.

Oxytocin and Reduction of Social Threat Hypersensitivity in Women With Borderline Personality Disorder

OBJECTIVE Patients with borderline personality disorder are characterized by emotional hyperarousal with increased stress levels, anger proneness, and hostile, impulsive behaviors. They tend to ascribe anger to ambiguous facial expressions and exhibit enhanced and prolonged reactions in response to threatening social cues, associated with enhanced and prolonged amygdala responses. Because the intranasal administration of the neuropeptide oxytocin has been shown to improve facial recognition and to shift attention away from negative social information, the authors investigated whether borderline patients would benefit from oxytocin administration. METHOD In a randomized placebo-controlled double-blind group design, 40 nonmedicated, adult female patients with a current DSM-IV diagnosis of borderline personality disorder (two patients were excluded based on hormonal analyses) and 41 healthy women, matched on age, education, and IQ, took part in an emotion classification task 45 minutes after intranasal administration of 26 IU of oxytocin or placebo. Dependent variables were latencies and number or initial reflexive eye movements measured by eye tracking, manual response latencies, and blood-oxygen-level-dependent responses of the amygdala to angry and fearful compared with happy facial expressions. RESULTS Borderline patients exhibited more and faster initial fixation changes to the eyes of angry faces combined with increased amygdala activation in response to angry faces compared with the control group. These abnormal behavioral and neural patterns were normalized after oxytocin administration. CONCLUSIONS Borderline patients exhibit a hypersensitivity to social threat in early, reflexive stages of information processing. Oxytocin may decrease social threat hypersensitivity and thus reduce anger and aggressive behavior in borderline personality disorder or other psychiatric disorders with enhanced threat-driven reactive aggression.

Grey matter abnormalities within cortico-limbic-striatal circuits in acute and weight-restored anorexia nervosa patients.

Functional disturbances within cortico-striatal control systems have been implicated in the psychobiology (i.e. impaired cognitive-behavioral flexibility, perfectionist personality) of anorexia nervosa. The aim of the present study was to investigate the morphometry of brain regions within cortico-striatal networks in acute anorexia nervosa (AN) as well as long-term weight-restored anorexia nervosa (AN-WR) patients. A total of 39 participants: 12 AN, 13 AN-WR patients, and 14 healthy controls (HC) underwent high-resolution, T1-weighted magnetic resonance imaging (MRI), a cognitive-behavioral flexibility task, and a psychometric assessment. Group differences in local grey matter volume (GMV) were analyzed using whole brain voxel-based morphometry (VBM) and brain-atlas based automatic volumetry computation (IBASPM). Individual differences in total GMV were considered as a covariate in all analyses. In the regional brain morphometry, AN patients, as compared to HC, showed decreased GMVs (VBM and volumetry) in the anterior cingulate cortex (ACC), the supplementary motor area (SMA), and in subcortical regions (amygdala, putamen: VBM only). AN-WR compared to HC showed decreased GMV (VBM and volumetry) in the ACC and SMA, whereas GMV of the subcortical region showed no differences. The findings of the study suggest that structural abnormalities of the ACC and SMA were independent of the disease stage, whereas subcortical limbic-striatal changes were state dependent.

Training cognitive flexibility in patients with anorexia nervosa: A pilot randomized controlled trial of cognitive remediation therapy

OBJECTIVE Inefficient cognitive flexibility is considered a neurocognitive trait marker involved in the development and maintenance of anorexia nervosa (AN). Cognitive Remediation Therapy (CRT) is a specific treatment targeting this cognitive style. The aim of this study was to investigate the feasibility and efficacy (by estimating the effect size) of specifically tailored CRT for AN, compared to non-specific cognitive training. METHOD A prospective, randomized controlled, superiority pilot trial was conducted. Forty women with AN receiving treatment as usual (TAU) were randomized to receive either CRT or non-specific neurocognitive therapy (NNT) as an add-on. Both conditions comprised 30 sessions of computer-assisted (21 sessions) and face-to-face (9 sessions) training over a 3-week period. CRT focused specifically on cognitive flexibility. NNT was comprised of tasks designed to improve attention and memory. The primary outcome was performance on a neuropsychological post-treatment assessment of cognitive set-shifting. RESULTS Data available from 25 treatment completers were analyzed. Participants in the CRT condition outperformed participants in the NNT condition in cognitive set-shifting at the end of the treatment (p = 0.027; between-groups effect size d = 0.62). Participants in both conditions showed high treatment acceptance. DISCUSSION This study confirms the feasibility of CRT for AN, and provides a first estimate of the effect size that can be achieved using CRT for AN. Furthermore, the present findings corroborate that neurocognitive training for AN should be tailored to the specific cognitive inefficiencies of this patient group.

Prolonged activation EEG differentiates dementia with and without delirium in frail elderly patients

Objective: Delirium in the elderly results in increased morbidity, mortality and functional decline. Delirium is underdiagnosed, particularly in dementia. To increase diagnostic accuracy, we investigated whether maintenance of activation assessed by EEG discriminates delirium in association with dementia (D+D) from dementia without delirium (DP) and cognitively unimpaired elderly subjects (CU). Method: Routine and quantitative EEG (rEEG/qEEG) with additional prolonged activation (3 min eyes open period) were evaluated in hospitalised elderly patients with acute geriatric disease. Patients were assigned post hoc to three comparable groups (D+D/DP/CU) by expert consensus based on DSM-IV criteria. Dementia diagnosis was confirmed using cognitive and functional tests and caregiver rating (IQCODE, Informed Questionnaire of Cognitive Decline in the Elderly). Results: While rEEG at rest showed low accuracy for a diagnosis of delirium, qEEG in DP and CU revealed a specific activation pattern of high significance found to be absent in the D+D group. Stepwise logistic regression confirmed that differentiation of D+D from DP was best resolved using activated upper alpha and delta power density which, compared with rEEG, enabled an 11% increase in diagnostic correctness to 83%, resulting in 67% sensitivity and 91% specificity. Among frail CU and D+D subjects, almost 90% were correctly classified. Conclusion: Dementia associated with delirium can be discriminated reliably from dementia alone in a meaningful clinical setting. Thus EEG evaluation in chronic encephalopathy should be optimised by a simple activation task and spectral analysis, particularly in the elderly with dementia.

Gender-specific strategy use and neural correlates in a spatial perspective taking task.

In the context of the present study spatial perspective taking refers to the ability to translocate ones own egocentric viewpoint to somebody elses viewpoint in space. We adopted a spatial perspective taking paradigm and performed a functional magnetic resonance imaging study to assess gender differences of neural activity during perspective taking. 24 healthy subjects (12 male/12 female) were asked to systematically either take their own (first-person-perspective, 1PP) or another persons perspective (third-person-perspective, 3PP). Presented stimuli consisted of a virtual scenery with an avatar and red balls around him that had to be counted, if visible, from 1PP or 3PP. Reaction time was increased and correctness scores were decreased during the cognitively more effortful 3PP condition. Correctness scores showed a trend towards a more pronounced decline of performance during 3PP as compared to 1PP in female subjects. Female subjects correctness scores declined by 6.7% from 1PP to 3PP, while in male subjects this performance decline was only 2.7%. Debriefings after the experiment, reaction times depending on angle of rotation and error rates suggest that males are more likely to employ an object-based strategy in contrast to a consistently employed egocentric perspective transformation in females. In the whole group, neural activity was increased in the parieto-occipital, right inferior frontal and supplementary motor areas, confirming previous studies. With respect to gender, male subjects showed stronger activation in the precuneus and the right inferior frontal gyrus than female subjects in a region-of-interest approach. In a subgroup of male subjects whose strategy reports suggest object-based strategies these differences seem to be more pronounced. In conclusion, the differential recruitment of brain regions most likely reflects different strategies in solving this spatial perspective taking task.

Intra-individual variability in high-functioning patients with schizophrenia.

Intra-individual variability of reaction times (IIV) can be employed as a measure of the stability of information processing, which has been proposed to be fundamentally disturbed in schizophrenia. However, the theoretical and clinical significance of IIV is not clear, in part because it has previously been investigated in subject groups with generalized cognitive impairment. Therefore, the purpose of the study was to assess IIV in high-functioning patients with schizophrenia and relatively preserved cognitive performance. 28 high-functioning patients with schizophrenia and 28 controls performed a Go/Nogo task and a Continuous Performance Test. In contrast to average measures of task performance, IIV differentiated consistently and with large effect size between groups. Modelling with an Ex-Gaussian distribution revealed that patients have a higher proportion of slow responses reflected by an increased tau parameter. The tau parameter was correlated with work capability in the sample with schizophrenia. In conclusion, IIV is an easily obtained measure, which is highly sensitive to fundamental cognitive deficits not directly visible in a high-functioning patient group. The response pattern with more exceedingly slow reactions could reflect a core deficit in the stability of information processing. The relationship with work capability suggests investigation of IIV as a clinical measure.

Motor impulsivity and the ventrolateral prefrontal cortex

Functional magnetic resonance imaging in a Go/Nogo task was employed to investigate the relationship between trait impulsivity and brain activation during motor response inhibition. We found a positive correlation between motor impulsivity and activation of bilateral ventrolateral prefrontal cortex during successful inhibitions, which suggests stronger recruitment to maintain task performance.

A supramodal network for response inhibition

Response inhibition is the capacity to suppress inappropriate actions and is considered to be a fundamental executive function. This study investigated whether the neural correlates of response inhibition are organized along supramodal or modality-specific principles. For this purpose, we used event-related functional magnetic resonance imaging in a go-nogo task with auditory and visual stimuli. Common activation relating to response inhibition across modalities was observed in a frontoparietal network including the ventrolateral prefrontal cortex. In contrast, there was no modality-specific activation related to response inhibition in the prefrontal cortex. These findings suggest that the neural correlates of response inhibition have a supramodal organization, which is consistent with its role as a core executive function.

Anorexia nervosa: selective processing of food-related word and pictorial stimuli in recognition and free recall tests.

OBJECTIVE Maladaptive processing of food cues is considered pivotal in the psychopathology of anorexia nervosa. However, the influence of hunger and differences in processing because of the type of stimuli remain largely unclear. METHOD Memory bias for food-related pictorial and semantic stimuli was assessed in a recognition and a free recall test in 16 anorexia nervosa (AN) patients, 16 control participants with food intake prior to the study (CG-FI) and 16 control participants with a fasting period prior to the study (CG-NF). RESULTS Compared with CG-FI participants, both AN and CG-NF participants responded faster to food-related as compared with neutral words (p < .001) in the recognition test. Differences were found for word but not for pictorial stimuli. No group differences were observed with respect to the number of correct retrievals in either the recognition or the free recall test. CONCLUSION The present study found behavioral indications of abnormal processing of food-related and neutral stimuli in anorectic patients similar to those found in fasted healthy controls. Results are discussed in terms of self-schemata in eating disorders, competitive interference, and levels of processing.