Attentional bias in depressive patients and the moderating effect of concurrent anxiety.

BACKGROUND: Most previous studies finding positive results in the emotional Stroop test did not control for concurrent anxiety symptoms. This study investigated depressive patients without comorbid anxiety disorders in order to clarify existing inconsistent findings. Furthermore, we examined the relationship between anxiety level and the emotional Stroop effect in patients and healthy subjects. SUBJECTS AND METHODS: Twenty-three depressive patients without comorbid anxiety disorder and 27 healthy subjects performed a mixed computerized version of the emotional Stroop test (attentional bias test). We assessed the state and trait anxiety and examined its correlation with the emotional Stroop effect. RESULTS: We failed to find evidence for attentional bias in the patients as measured by longer reaction times to the emotional stimuli. However, there was a positive correlation between state anxiety and attentional bias in depressed patients. On the other hand, in healthy subjects the trait anxiety correlated negatively with attentional bias. CONCLUSIONS: Attentional bias is not found in depressed patients if only patients without comorbid anxiety disorders are included. Furthermore, healthy subjects with high trait anxiety levels may be vulnerable to affective disorders because they use avoidance strategies when encountering negative information.

Pain ratings and somatosensory evoked responses to repetitive intramuscular and intracutaneous stimulation in fibromyalgia syndrome.

To determine the presence of perceptual sensitization and related brain responses we examined 15 patients with fibromyalgia syndrome and 15 healthy controls comparable in age and sex. Multichannel EEG recordings and pain ratings were obtained during the presentation of 800 painful electrical intramuscular and intracutaneous stimuli to the left m. erector spinae and the left m. extensor digitorum. The stimulus intensity was adjusted to 50% between pain threshold and tolerance. Detection and pain thresholds were significantly lower in the fibromyalgia syndrome group. Sensitization occurred for both groups during intramuscular stimulation. In the EEG data the fibromyalgia syndrome patients showed higher N80 amplitudes compared with the healthy controls. Arm stimulation and intramuscular stimulation yielded higher N80 and N150 amplitudes compared with intracutaneous stimulation or stimulation of the back. These results indicate lower pain thresholds in the fibromyalgia syndrome patients after electrical stimulation and a higher N80 amplitude both indicative of enhanced sensory processing in this group.

Stroop performance in depressive patients: a preliminary report.

BACKGROUND: The Stroop interference test requires executive control functions, in particular inhibition of a learned routine (in this case word reading). Depressive patients show deficits on tests of executive function. However, the impact of confounding variables like type of depression and anxiety level is not yet elucidated for depressive patients. This is of clinical importance, since executive functions seem to play an important role in predicting treatment response and functional outcome. METHODS: 23 depressive patients and 27 healthy subjects performed a computerized mixed trial Stroop task. Depressive patients were divided according to DSM-IV diagnosis into melancholic and non-melancholic subgroups. Furthermore the level of anxiety was assessed in all subjects. RESULTS: When depressed patients were analyzed as a whole group, they showed only a trend towards higher Stroop interference effect at the beginning of the task. When analysis was performed using according to DSM-IV defined melancholic and non-melancholic subgroups, only non-melancholic patients were impaired in the Stroop task compared to melancholic patients and healthy subjects. LIMITATIONS: The sample size was small resulting in low statistical power. Furthermore, the patients were medicated. CONCLUSIONS: The unexpected result that melancholic patients perform better than non-melancholic ones may be due to their more pronounced rigidity, which makes them more resistant against distraction. Hence, more detailed psychopathological assessment is desirable for future investigations in executive functions of melancholic patients.

N2 event-related potential correlates of response inhibition in an auditory Go/Nogo task.

The aim of this study was to investigate the event-related potential correlates of response inhibition in the N2 time window, specifically in the auditory modality. A paired tone Go/Nogo paradigm elicited an enhanced fronto-central negativity in the Nogo condition, which was accompanied by a concurring inferior fronto-temporal positivity. In contrast to most previous studies our data provide evidence for a fronto-central Nogo-N2 component in the auditory modality.

Prefrontal-cingulate activation during executive control: which comes first?

The Stroop test requires executive control functions, in particular inhibition of a learned routine (in this case, word reading). The spatiotemporal analysis of brain activation during Stroop task execution was performed in 16 healthy subjects using high-density event-related potentials (ERPs) and dipole source modeling (BESA software). Scalp ERP analysis revealed the neurophysiological substrate of the interference effect: first, a greater negativity in the incongruent as compared to the congruent and neutral conditions was found between 350 and 450 ms poststimulus over left frontocentral scalp regions. Source analysis of the difference wave (incongruent-congruent) indicated that a generator localized in left prefrontal cortex (PFC) contributed to this effect. Second, immediately after the first effect, a greater positivity in the incongruent as compared to the congruent and neutral conditions developed between 450 and 550 ms poststimulus over midline frontocentral scalp regions. A generator of this effect was located in right anterior cingulate cortex (ACC). ACC activation seems to follow the activation of PFC with some overlap between the two components. Possible interpretation of this finding is that PFC signals ACC when executive control is required and ACC implements the control.

Stroop interference effect in schizophrenic patients: an electrophysiological approach.

Schizophrenic patients present deficits in executive control functions. The Stroop test requires executive control functions, in particular response inhibition. So far only one study has employed the high temporal resolution of electrophysiological methods to investigate the neural correlates of the Stroop effect in schizophrenia. This study investigated medicated patients with schizophrenia or schizoaffective disorder (n=15) and healthy controls (n=15) using event-related potentials. The analyses of the P1 and N1 components revealed no differences between the groups indicating intact sensory processing in schizophrenia during the Stroop test. We found greater negativity in the incongruent as compared to the congruent and neutral conditions between 350 and 450 ms over prefrontal scalp areas in healthy subjects but not in schizophrenic patients. Later on, a sustained positivity was observed over parietal scalp regions in healthy subjects. This later sustained potential was attenuated in patients but only in the first block. This suggests that following practice patients show similar parietal effects as healthy subjects. The total errors in the incongruent condition in patients correlated negatively with the difference in mean activity between incongruent and congruent conditions over the left parietal area (time window 600-1000 ms). In other words the more errors were made by patients, the more attenuated was the Stroop related electrophysiological effect. This suggests that the parietal activity is related to successful resolution of the Stroop conflict in schizophrenic patients. Furthermore, the absence of the frontal deflection in patients reflects dysfunctional neural processes associated with executive control.