No abstract

Momentary brain electric field configurations are manifestations of momentary global functional states of the brain. Field configurations tend to persist over some time in the sub-second range ("microstates") and concentrate within few classes of configurations. Accordingly, brain field data can be reduced efficiently into sequences of re-occurring classes of brain microstates, not overlapping in time. Different configurations must have been caused by different active neural ensembles, and thus different microstates assumably implement different functions. The question arises whether the aberrant schizophrenic mentation is associated with specific changes in the repertory of microstates. Continuous sequences of brain electric field maps (multichannel EEG resting data) from 9 neuroleptic-naive, first-episode, acute schizophrenics and from 18 matched controls were analyzed. The map series were assigned to four individual microstate classes; these were tested for differences between groups. One microstate class displayed significantly different field configurations and shorter durations in patients than controls; degree of shortening correlated with severity of paranoid symptomatology. The three other microstate classes showed no group differences related to psychopathology. Schizophrenic thinking apparently is not a continuous bias in brain functions, but consists of intermittent occurrences of inappropriate brain microstates that open access to inadequate processing strategies and context information

The present study contributes to the current debate about electrophysiological measurements of mental workload. Specifically, the allocation of attentional resources during different complexity levels of tasks and its changes over time are of great interest. Therefore, we investigated mental workload using tasks varying in difficulty during an auditory oddball target paradigm. For data analysis, we applied a novel method to compute event-related potentials (ERPs) by intra-block epoch averaging of P2, P3a and P3b amplitude components for the infrequent target stimuli. We obtained eight consecutive blocks of 5 epochs each, which allowed us to develop an electrophysiological parameter to measure mental workload. In both the easy and the more constraining tasks, the amplitude of P2 decreased beginning with the second block of the sequence. In contrast, the amplitudes of P3a and P3b components linearly decreased following the repetition of the target in the more constraining task, but not in the easy task. Statistical analysis revealed intra-block differences on amplitudes of ERPs of interest between the easy and the more constraining tasks, confirming this method as a measure to assess mental workload. Since a subject is his own control, the present method represents an electrophysiological parameter for individual measurement of mental workload and may therefore be applicable in clinical routine.

The 24-item Brief Psychiatric Rating Scale (BPRS, version4.0) enables the rater to measure psychopathology severity. Still, little is known about the BPRS's reliability and validity outside of the psychosis spectrum. The aim of this study was to examine the factorial structure and sensitivity to change of the BPRS in patients with unipolar depression. Two hundred and forty outpatients with unipolar depression were administered the 24-item BPRS. Assessments were conducted at intake and at post-treatment in a Crisis Intervention Centre. An exploratory factor analysis of the 24-item BPRS produced a six-factor solution labelled “Mood disturbance”, “Reality distortion”, “Activation”, “Apathy”, “Disorganization”, and “Somatization”. The reduction of the total BPRS score and dimensional scores, except for “Activation”, indicates that the 24-item BPRS is sensitive to change as shown in patients that appeared to have benefited from crisis treatment. The findings suggest that the 24-item BPRS could be a useful instrument to measure symptom severity and change in symptom status in outpatients presenting with unipolar depression.

Several patterns of grey and white matter changes have been separately described in young adults with first-episode psychosis. Concomitant investigation of grey and white matter densities in patients with first-episode psychosis without other psychiatric comorbidities that include all relevant imaging markers could provide clues to the neurodevelopmental hypothesis in schizophrenia