Cortical interactions during the experience of auditory verbal hallucinations.

Auditory verbal hallucinations (AVHs), the perception of voices in the absence of auditory stimuli, are common and distressing symptoms reported by 50%-80% of patients with schizophrenia. However, the results in a number of imaging and electrophysiological studies on the origins of AVH are not consistent, and the underlying pathophysiology remains unclear. The authors enrolled a group of schizophrenia patients and normal-control subjects, age 18-45 years. Two patient groups participated in the study; 1) a group of 8 patients with drug-resistant spontaneous AVHs; and 2) a group of 7 patients whose AVHs were successfully controlled with neuroleptic medication; along with 16 normal-control subjects. The entire sample had EEG recording done, with the AVH group told to press a button when they experienced a hallucination, and the other two groups randomly told when to press the button. In the AVH group, hallucinations were longer in the "eyes-closed" than "eyes-open" condition. There was spreading phase-coupling in the AVH group, intra- and inter-hemispherically, at left and right frontal and temporal areas, under both eyes-closed and eyes-open condition, during the experience of AVH. There was a statistically significant increase of α-band frequency-specific synchrony maximum values in the AVH group. AVHs are considered to be complex features, and, as such, they reflect abnormal functional connectivity in multiple related regions in both intra- and inter-hemispherical brain sites, primarily defined by phase-integration.

Indication of Disrupted Temporal Structure in the Case of Thought Blocks in Schizophrenia: The Role of the Metastable Balance.

This study is aimed at investigating probable disruption of the metastable balance relevant to a disruption of the mental processes observed in the neurophenomenal level. This disruption was found to occur under dense auditory verbal hallucinations (AVHs) which are accompanied by thought blocking (TB) phenomena. The entropy that quantifies the complexity of the spontaneous coupling has been used to describe the observed transitions. According to our findings, the high synchrony-derived entropy (SE) defines a metastable state, where formations of cortical areas are able to coordinate transiently under the demands of stimulus-oriented processes or other internal cognitive associations. It was also found that the disruption of the sensitive balance to the side of oversynergy (overconnectedness) rather than the side of independence (coincidental coupling) is relevant with functional fixations under the specific symptom of schizophrenia. An introduced measure relative to the persistence of coupling indicated that the overcoupled brain areas exhibit a kind of "stiffness" in processing incoherent phasic components. Our consideration enhances the understanding of the role the metastability plays in the interpretation of deeply subjective phenomena, such as AVHs and TBs that affect the normal information routing in the brain.

The persistent and broadly distributed EEG synchronization might inhibit the normal processing capability of the human brain.

Synchrony in the brain functioning describes the mode that the components are interacted and reflect the collective behaviour of neuronal assemblies. Nevertheless, the excessive and prolonged coupling among brain sites is relevant with disturbed information routing. In the present study we investigated the possibility that the sustained oscillatory states and the common mode in which several brain sites vary their functional connectivity inhibit the ability of the brain in perceiving and processing information. The hypothesis, that in many interacting systems, greater regularity-rhythmicity corresponds to grater component self-organization and isolation, is investigated in the case of thought blocks (under persistent auditory verbal hallucinations) and epileptic absences (under spike wave discharges). Our findings indicate that the observed common mode of coupling significantly restrains the normal flow of mental processes. This erroneous "connectivity mode" in the presence of symptoms such as thought blocks and absences respectively, was found to eliminate the spontaneous synchrony variability, essentially needed for the information processing, by fixating the functional specificity of the respected brain sites.

Mood regulation in bipolar disorders viewed through the pendulum dynamics concept.

Bipolar disorders have been characterized by powerful fluctuations of energy, mood, and thinking patterns. Mood episodes (manic or depressive) could be considered as deviations of a psycho-physiological index above or below a conventionally defined value called 'normothymia'. In the present study, we analyzed the feedback techniques used to suppress the oscillatory activity exhibited on an inverted pendulum device. Subsequently, we examine the degree that this multimodal feedback design could be considered on a hypothetical pendulum where the mood plays the role of the suspended mass, and the force balance compensation circuitry is substituted by drug-specific therapeutic interventions. The study does not concern a model of bipolar illness that could simulate numerically various phases of mood episodes but focuses on the functional similarities regarding the correction treatments applied on the two different oscillating systems giving a potential perspective of how techniques of feedback control may enhance the conceptualization of the treatment schemes followed in recent guidelines for biological treatment of bipolar disorders. Our theoretical consideration, along with observations on clinical level, gives support to the concept that the compensation of the mood oscillations should be adaptive with selective therapeutic interventions that compensate the excited system in different time scales.

Brain functional connectivity during the experience of thought blocks in schizophrenic patients with persistent auditory verbal hallucinations: an EEG study.

Thought blocks (TBs) are characterized by regular interruptions in the stream of thought. Outward signs are abrupt and repeated interruptions in the flow of conversation or actions while subjective experience is that of a total and uncontrollable emptying of the mind. In the very limited bibliography regarding TB, the phenomenon is thought to be conceptualized as a disturbance of consciousness that can be attributed to stoppages of continuous information processing due to an increase in the volume of information to be processed. In an attempt to investigate potential expression of the phenomenon on the functional properties of electroencephalographic (EEG) activity, an EEG study was contacted in schizophrenic patients with persisting auditory verbal hallucinations (AVHs) who additionally exhibited TBs. In this case, we hypothesized that the persistent and dense AVHs could serve the role of an increased information flow that the brain is unable to process, a condition that is perceived by the person as TB. Phase synchronization analyses performed on EEG segments during the experience of TBs showed that synchrony values exhibited a long-range common mode of coupling (grouped behavior) among the left temporal area and the remaining central and frontal brain areas. These common synchrony-fluctuation schemes were observed for 0.5 to 2s and were detected in a 4-s window following the estimated initiation of the phenomenon. The observation was frequency specific and detected in the broad alpha band region (6-12Hz). The introduction of synchrony entropy (SE) analysis applied on the cumulative synchrony distribution showed that TB states were characterized by an explicit preference of the system to be functioned at low values of synchrony, while the synchrony values are broadly distributed during the recovery state. Our results indicate that during TB states, the phase locking of several brain areas were converged uniformly in a narrow band of low synchrony values and in a distinct time window, impeding thus the ability of the system to recruit and to process information during this time window.

Indication of increased phase coupling between theta and gamma EEG rhythms associated with the experience of auditory verbal hallucinations.

Electroencephalographic oscillations, with different spectral contents, recorded in various brain sites are assumed to play an important role in the information processes underlying cognition as well as the abnormal brain functioning observed in nosological entities that affect neuronal connectivity such as schizophrenia. In the present study we investigated the interaction of EEG rhythms during the experience of auditory verbal hallucinations (AVHs). For this purpose we analyzed data obtained from patients suffering from persistent AVHs, focusing on the mode that the phase of theta oscillations modulate the amplitude of the broad gamma EEG oscillations. Our results indicate increased phase coupling between theta and gamma rhythms observed in the left frontotemporal cortices during AVHs, under eyes closed condition. The average differences of theta-gamma coupling between hallucinatory and resting stages in the left temporal area were found to be statistically significant. These results suggest that a theta-gamma interaction may be involved in the production and experience of AVHs in patients suffering from schizophrenia.