Beyond aphasia: Altered EEG connectivity in Broca's patients during working memory task.

Broca's region and adjacent cortex presumably take part in working memory (WM) processes. Electrophysiologically, these processes are reflected in synchronized oscillations. We present the first study exploring the effects of a stroke causing Broca's aphasia on these processes and specifically on synchronized functional WM networks. We used high-density EEG and coherence analysis to map WM networks in ten Broca's patients and ten healthy controls during verbal WM task. Our results demonstrate that a stroke resulting in Broca's aphasia also alters two distinct WM networks. These theta and gamma functional networks likely reflect the executive and the phonological processes, respectively. The striking imbalance between task-related theta synchronization and desynchronization in Broca's patients might represent a disrupted balance between task-positive and WM-irrelevant functional networks. There is complete disintegration of left fronto-centroparietal gamma network in Broca's patients, which could reflect the damaged phonological loop.

Corticospinal and transcallosal modulation of unilateral and bilateral contractions of lower limbs.

PURPOSE: Interhemispheric inhibition may play a role in the expression of bilateral deficit in force (BLD). This study investigated whether the degree of BLD is reflected in the nature of interhemispheric interaction during unilateral and bilateral contractions. METHODS: Subjects divided into three groups, 'bilateral' (n = 7), 'unilateral' (n = 5) and 'control' (n = 8), performed unilateral and bilateral maximal voluntary isometric knee extensions while receiving electrical stimulation, and transcranial magnetic stimulation of the target and ipsilateral muscles. Main variables of interest included peak force for subsequent calculation of bilateral index, voluntary activation level (VAL), motor evoked potential amplitudes (MEPs) and silent period durations (SPs). RESULTS: BLD was noted only for the whole sample (p = 0.009), but not for any of the groups. VAL was significantly higher during bilateral compared to unilateral contractions (~97 vs. 92 %, p = 0.023), with no differences between groups. MEPs of target and ipsilateral muscles were significantly bigger during bilateral contractions (p = 0.042 and p = 0.022, respectively), with no differences between groups. No differences in SPs were observed. CONCLUSIONS: Higher values of MEPs and VAL during bilateral contractions, in conjunction with unaltered SPs, do not support the concept of inhibition related to BLD, but rather suggest the possibility of cortical facilitation. Based on the existing literature, this behavior may be specific to the lower limb musculature, but the possibility of sub-cortical or higher-order neural alterations cannot be excluded.

The electrophysiological correlates of the working memory subcomponents: evidence from high-density EEG and coherence analysis.

Synchronization between prefrontal (executive) and posterior (association) cortices seems a plausible mechanism for temporary maintenance of information. However, while EEG studies reported involvement of (pre)frontal midline structures in synchronization, functional neuroimaging elucidated the importance of lateral prefrontal cortex (PFC) in working memory (WM). Verbal and spatial WM rely on lateralized subsystems (phonological loop and visuospatial sketchpad, respectively), yet only trends for hemispheric dissociation of networks supporting rehearsal of verbal and spatial information were identified by EEG. As oscillatory activity is WM load dependent, we applied an individually tailored submaximal load for verbal (V) and spatial (S) task to enhance synchronization in the relevant functional networks. To map these networks, we used high-density EEG and coherence analysis. Our results imply that the synchronized activity is limited to highly specialized areas that correspond well with the areas identified by functional neuroimaging. In both V and S task, two independent networks of theta synchronization involving dorsolateral PFC of each hemisphere were revealed. In V task, left prefrontal and left parietal areas were functionally coupled in gamma frequencies. Theta synchronization thus provides the necessary interface for storage and manipulation of information, while left-lateralized gamma synchronization could represent the EEG correlate of the phonological loop.

Differentiation of psychotic from nonpsychotic psychiatric inpatients: the Rorschach Perceptual Thinking Index.

The aim of the study was to investigate the validity of the Rorschach Perceptual Thinking Index (PTI) to detect psychotic perceptual and thought disturbance in a sample of Slovene psychiatric inpatients. Using a sample of 275 adult psychiatric inpatients of both sexes, we examined the differences between patients with psychosis (PP) and patients with no psychotic features (NP) from various diagnostic groups on the global PTI and its subcomponent variables. PPs obtained significantly higher PTI scores, indicating more disturbed perception and more thinking disturbance, than NPs. No differences were found for diagnostic differences within the PP and NP groups. Results are in accordance with previous studies of the PTI as a valid cross-cultural index of perceptual and thinking disturbance.

Genome-wide expression changes in a higher state of consciousness.

Higher states of consciousness in which the human mind can transcend the boundaries of logic and reason are envisioned as natural to the experience and potential growth of every human being. So far they have been mostly monitored by electrophysiological methods. In this study we were particularly interested in discovering the molecular transcriptional basis of higher states of consciousness. In addition to phenomenological reports of meditators who participated in this study the generated higher states of consciousness were also EEG recorded. We assessed the whole genome gene expression analysis of long-term meditators in four separate trials and detected significant differential gene expression in association with higher states of consciousness. The number of differently expressed genes as well as high proportion of genes themselves differed between meditators. Despite this, gene ontology enrichment analysis found significant biological and molecular processes shared among meditators' higher state of consciousness.