[show abstract][hide abstract] ABSTRACT: Smoking prevalence is highly elevated in schizophrenia compared to the general population and to other psychiatric populations. Evidence suggests that smoking may lead to improvements of schizophrenia-associated attention deficits; however, large-scale studies on this important issue are scarce. We examined whether sustained, selective, and executive attention processes are differentially modulated by long-term nicotine consumption in 104 schizophrenia patients and 104 carefully matched healthy controls. A significant interaction of 'smoking status' × 'diagnostic group' was obtained for the domain of selective attention. Smoking was significantly associated with a detrimental conflict effect in controls, while the opposite effect was revealed for schizophrenia patients. Likewise, a positive correlation between a cumulative measure of nicotine consumption and conflict effect in controls and a negative correlation in patients were found. These results provide evidence for specific directional effects of smoking on conflict processing that critically dissociate with diagnosis. The data supports the self-medication hypothesis of smoking in schizophrenia and suggests selective attention as a specific cognitive domain targeted by nicotine consumption. A potential mechanistic model explaining these findings is discussed.
[show abstract][hide abstract] ABSTRACT: The Attention Network Test (ANT) is a well established behavioral measure in neuropsychological research to assess three different facets of selective attention, i.e., alerting, orienting, and conflict processing. Although the ANT has been applied in healthy individuals and various clinical populations, data on retest reliability are scarce in healthy samples and lacking for clinical populations. The objective of the present study was a longitudinal assessment of relevant ANT network measures in healthy controls and schizophrenic patients.
Forty-five schizophrenic patients and 55 healthy controls were tested with ANT in a test-retest design with an average interval of 7.4 months between test sessions. Test-retest reliability was analyzed with Pearson and Intra-class correlations.
Healthy controls revealed moderate to high test-retest correlations for mean reaction time, mean accuracy, conflict effect, and conflict error rates. In schizophrenic patients, moderate test-retest correlations for mean reaction time, orienting effect, and conflict effect were found. The analysis of error rates in schizophrenic patients revealed very low test-retest correlations.
The current study provides converging statistical evidence that the conflict effect and mean reaction time of ANT yield acceptable test-retest reliabilities in healthy controls and, investigated longitudinally for the first time, also in schizophrenia. Obtained differences of alerting and orienting effects in schizophrenia case-control studies should be considered more carefully. The analysis of error rates revealed heterogeneous results and therefore is not recommended for case control studies in schizophrenia.
Schizophrenia Research 12/2011; 133(1-3):218-22. · 4.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: In the search for markers of schizophrenia, functional deficits during inhibition have been a major focus. In previous studies, we found a reduced amplitude modulation of the visual P3 component of the event-related potential (ERP) in schizophrenic patients during inhibition in the Attention Network Test (ANT). The objective of the present study was to explore whether this deficit exhibits properties of a trait or state marker of schizophrenia.
Eighteen recent onset inpatients and eighteen chronic schizophrenic outpatients as well as 36 healthy controls, including a young adult and an old adult group to match recent onset and chronic illness groups for age and sex, were included. Participants were tested with ANT while 32-channel electroencephalogram was recorded and visual P3 amplitudes were analyzed. Amplitude modulation was defined as the variation of P3 amplitude at Pz as a function of ANT flanker conditions.
There were no significant behavioral between-group differences in terms of alerting, orienting, and inhibition. Mean visual P3 was significantly lower in schizophrenic patients than in healthy controls. Parietal P3 amplitude was significantly less modulated in both recent onset (-0.035) and chronic schizophrenic patients (-0.081) compared with young (-0.588; p<0.05) and older healthy controls, respectively (-0.556; p<0.05). No correlations were obtained between P3 modulation and clinical or demographic variables.
The results provide evidence that the observed deficit of visual P3 amplitude modulation is independent of duration of illness and age and may contain properties of a trait marker of schizophrenia.
Schizophrenia Research 03/2011; 130(1-3):210-5. · 4.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: To characterize the interplay of bottom-up and top-down processing deficits of the early visual ERP component N1 in schizophrenia.
Thirty-three schizophrenic patients and 61 healthy controls underwent a visual selective attention paradigm while 32-channel electroencephalogram was recorded. Visual N1 responses were calculated and source localization was applied.
Significant reductions of the cue N1 as well as the target N1 components were found in schizophrenia patients. Linear regression slopes for the cue N1 and for the cue-locked target N1 indicated significantly reduced early bottom-up and top-down modulation in patients relative to controls. Source analyses indicated that bottom-up as well as top-down N1 deficits in schizophrenia are associated with partially overlapping current density deficits in posterior cortex areas. Differential functional deficits were observed in right parietal lobe during bottom-up processing and in anterior cingulate cortex during top-down attention.
The results provide evidence for both early visual bottom-up and top-down deficits in schizophrenia and illustrate how disturbances in these processing streams converge on the visual N1 amplitude.
Visual top-down disturbances in schizophrenia appear to be confounded by visual bottom-up deficits.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 01/2011; 122(1):90-8. · 3.12 Impact Factor
[show abstract][hide abstract] ABSTRACT: Selective visual attention is thought to be comprised of distinct neuronal networks that serve different attentional functions. The Attention Network Test (ANT) has been introduced to allow for assessment of alerting, orienting, and response inhibition. Information on associated measures of neural processing during ANT is still scarce. We topographically analyzed top-down ANT effects on visual event-related potential morphology in 44 healthy participants. Significant reaction time effects were obtained for all attention networks. Posterior cue-locked target N1 amplitude was significantly increased during both alerting and orienting. P3 amplitude was significantly modulated at frontal and parietal leads as a function of inhibition. Our data suggests that attentional mechanisms of alerting and orienting are employed simultaneously at early stages of the visual processing stream to amplify perceptual discrimination and load onto the same ERP component. Fronto-parietal modulations of P3 amplitude seem to mirror both response inhibition and visual target detection and may be interesting markers for further studies.
International journal of psychophysiology: official journal of the International Organization of Psychophysiology 02/2010; 76(2):72-9. · 3.05 Impact Factor
[show abstract][hide abstract] ABSTRACT: Attention is one of the cognitive domains typically affected in multiple sclerosis. The Attention Network Test was developed to measure the function of the three distinct attentional networks, alerting, orienting, and executive control. The Attention Network Test has been performed in various neuropsychiatric conditions, but not in multiple sclerosis. Our objective was to investigate functions of attentional networks in multiple sclerosis by means of the Attention Network Test. Patients with relapsing-remitting multiple sclerosis (n = 57) and healthy controls (n = 57) matched for age, sex, and education performed the Attention Network Test. Significant differences between patients and controls were detected in the alerting network (p = 0.003), in contrast to the orienting (p = 0.696) and the conflict (p = 0.114) network of visual attention. Mean reaction time in the Attention Network Test was significantly longer in multiple sclerosis patients than in controls (p = 0.032), Multiple sclerosis patients benefited less from alerting cues for conflict resolution compared with healthy controls. The Attention Network Test revealed specific alterations of the attention network in multiple sclerosis patients which were not explained by an overall cognitive slowing.
[show abstract][hide abstract] ABSTRACT: Associations between the well-known functional single nucleotide polymorphism Val (158)Met in the gene encoding catechol- O-methyltransferase (COMT) and cognitive do-mains affected in schizophrenia are inconsistent regarding directionality and specific impact and call for a more fundamental cognitive endophenotype. Recent studies suggest that the COMT genotype contributes to cognitive flexibility, a fundamental cognitive ability that potentially influences an individual's performance in a variety of other neurocognitive tasks.
We investigated the association between COMT Val (158)Met genotype and cognitive flexibility as assessed by signal discrimination in the Continuous Performance Test - Identical Pairs version in a cohort of 111 German schizophrenic patients.
COMT genotype was significantly associated with signal discrimination index d' in schizophrenia. The Val/Val genotype was associated with the highest and the Met/Met genotype with the lowest scores; heterozygous individuals displayed an intermediate performance.
Our data suggest that allelic variation at the COMT Val (158)Met locus may influence signal discrimination capacity in schizophrenia and confirm that Val loading, probably due to decreased prefrontal dopamine availability, is associated with greater cognitive flexibility, which in turn may influence other cognitive measures that have been associated with COMT to date.
[show abstract][hide abstract] ABSTRACT: Functional neuroimaging studies have increasingly aimed at approximating neural substrates of human cognitive sex differences elicited by visuospatial challenge. It has been suggested that females and males use different behaviorally relevant neurocognitive strategies. In females, greater right prefrontal cortex activation has been found in several studies. The spatiotemporal dynamics of neural events associated with these sex differences is still unclear. We studied 22 female and 22 male participants matched for age, education, and nicotine with 29-channel-electroencephalogram recorded under a visual selective attention paradigm, the Attention Network Test. Visual event-related potentials (ERP) were topographically analyzed and neuroelectric sources were estimated. In absence of behavioral differences, ERP analysis revealed a novel frontal-occipital second peak of visual N100 that was significantly increased in females relative to males. Further, in females exclusively, a corresponding central ERP component at around 220 ms was found; here, a strong correlation between stimulus salience and sex difference of the central ERP component amplitude was observed. Subsequent source analysis revealed increased cortical current densities in right rostral prefrontal (BA 10) and occipital cortex (BA 19) in female subjects. This is the first study to report on a tripartite association between sex differences in ERPs, visual stimulus salience, and right prefrontal cortex activation during attentional processing.
Human Brain Mapping 02/2009; 30(9):2997-3008. · 6.88 Impact Factor