The contingent negative variation laterality and dynamics in antisaccade task in normal and unmedicated schizophrenic subjects.

Contingent negative variation (CNV) topography, hemispheric asymmetry and time-course were investigated in healthy subjects and non-medicated paranoid schizophrenic patients in two antisaccade paradigms with the short (800-1000 ms) and long (1200-1400 ms) durations of the fixation period. EEG and electrooculogram (EOG) were recorded. Saccade characteristics and mean amplitudes of slow cortical potentials time-locked to peripheral target were analyzed in 23 healthy volunteers and 19 schizophrenic patients. Compared to healthy control subjects, schizophrenic patients had significantly slower antisaccades and committed significantly more erroneous saccades in the both antisaccade tasks. The prolongation of the fixation period resulted in noticeable decrease of error percent in patients group. The analysis of CNV time-course has revealed two distinct stages in both groups. The early CNV stage was represented by a negative wave with the maximal amplitude over midline fronto-central area, and the late stage was characterized by increased CNV amplitude at the midline and left parietal electrode sites. In healthy subjects the simultaneous activation of frontal and parietal areas was observed in the paradigm with the shorter fixation interval; the increase of the fixation period produced consecutive activation of these areas. Schizophrenic patients' CNV amplitude was generally smaller than that of healthy subjects. The most pronounced between-group differences of the negative shift amplitude were revealed at frontal electrode sites during the early CNV stage in both modifications of the antisaccade task. The deficit of frontal activation revealed in patients at the early stage of antisaccade preparatory set in both antisaccadic paradigms may be related to pathogenesis of paranoid schizophrenia.

Sensorimotor and sensory gating in depression, anxiety, and their comorbidity.

OBJECTIVES: Abnormal attentional and cognitive processes are thought to increase the risk for depression and anxiety. To improve understanding of brain mechanisms of anxiety and depressive disorders and condition of their comorbidity, the study of early attentional processes was provided. METHODS: Participants were patients with depressive (80 s.), anxiety (69 s.), and comorbid (41 s.) disorders, and healthy volunteers (50 s.). Acoustic startle response (ASR) and P50 component of the auditory event-related potential were recorded. RESULTS: In the ASR model decreased startle response amplitude at the left eye in patients with comorbid disorder was found, and ASR latency was lengthened in all clinical groups. Deficit of prepulse inhibition was unique for comorbid disorder, and might be considered as risk of evolution to more serious condition. Reduced prepulse facilitation was revealed in patients with comorbid and anxiety disorders. In P50 suppression paradigm decreased S1 response amplitude was revealed in all clinical groups, P50 latency was prolonged in depressive and comorbid patients, and P50 suppression deficit was observed in depression and anxiety groups. CONCLUSIONS: The obtained results might be useful for development of integrative neural models of comorbidity of anxiety and depression, and elaboration of diagnostic and therapeutic approaches.

Mu rhythm separation from the mix with alpha rhythm: Principal component analyses and factor topography.

BACKGROUND: EEG mu rhythm suppression is assessed in experiments on the execution, observation and imagination of movements. It is utilised for studying of actions, language, empathy in healthy individuals and preservation of sensorimotor system functions in patients with schizophrenia and autism spectrum disorders. While EEG alpha and mu rhythms are recorded in the same frequency range (8-13 Hz), their specification becomes a serious issue. THE NEW METHOD: is based on the spatial and functional characteristics of the mu wave, which are: (1) the mu rhythm is located over the sensorimotor cortex; (2) it desynchronises during movement processing and does not respond on the eyes opening. In EEG recordings, we analysed the mu rhythm under conditions with eyes opened and eyes closed (baseline), and during a motor imagery task with eyes closed. EEG recordings were processed by principal component analysis (PCA). RESULTS: The analysis of EEG data with the proposed approach revealed the maximum spectral power of mu rhythm localised in the sensorimotor areas. During motor imagery, mu rhythm was suppressed more in frontal and central sites than in occipital sites, whereas alpha rhythm was suppressed more in parietal and occipital sites. Mu rhythm desynchronization in sensorimotor sites during motor imagery was greater than alpha rhythm desynchronization. The proposed method enabled EEG mu rhythm separation from its mix with alpha rhythm. CONCLUSIONS: EEG mu rhythm separation with the proposed method satisfies its classical definition.

AUDITORY EVOKED POTENTIALS EVIDENCE FOR DIFFERENCES IN INFORMATION PROCESSING BETWEEN HIGH AND LOW HYPNOTIZABLE SUBJECTS.

N100 and P300 auditory evoked potentials in 2-stimulus oddball paradigm were analyzed in high (HH, n = 18) and low (LH, n = 15) hypnotizable participants under waking condition. LH subjects committed more errors than HH subjects. HH subjects demonstrated shorter N100 latencies at frontal electrodes and significant N100 differences between target and nontarget stimuli (higher N100 amplitude and increased latency at parietal sites to targets vs. nontargets), whereas LH subjects failed to show any differences. The overall increase of P300 amplitude with frontal-central localization of P300 maximum was found in HH subjects compared to LH subjects. The obtained results support the psychophysiological model of HH individuals having more effective frontal attentional systems involved in detecting, integrating, and filtering relevant information.

COMT Genotype and Sensory and Sensorimotor Gating in High and Low Hypnotizable Subjects.

We investigated the association between hypnotizability, COMT polymorphism, P50 suppression ratio, and prepulse inhibition of acoustic startle response (ASR) in 21 high (HH) and 19 low (LH) hypnotizable subjects. The frequency of Met/Met carriers of COMT polymorphysm was higher in HH than in LH group (33.3% versus 10.6%, p = .049). Increased ASR amplitude and latency and decreased prepulse inhibition at 120 ms lead interval were found in the HH compared to the LH group. The effect of COMT genotype on prepulse inhibition was observed in LH group only. No between-group differences in P50 measures were found. The obtained results suppose the participation of dopamine system in mechanisms of hypnotizability and different allocation of attentional resources in HH and LH subjects.

EEG coherence in a mental arithmetic task performance in first episode schizophrenia and schizoaffective disorder.

OBJECTIVES: To evaluate the coherence values of the cortical bands in patients with first episode schizophrenia and schizoaffective disorder during the performance of a mental arithmetic task. METHOD: We analysed EEG coherence in the resting state and subsequently while counting down from 200 in steps of 7 in 32 first episode schizophrenia patients (SZ), 32 patients with first episode schizoaffective disorder (SA) and 40 healthy controls (HC). RESULTS: Task performance in HC is characterised by decreased coherence in the alpha bands and increased coherence in the beta 2 and gamma bands in frontal sites. In SZ, coherence decreases in the alpha band, whereas in SA it substantially increases in the alpha, beta1, beta 2 and gamma bands. CONCLUSIONS: Despite no differences in performance on a behavioural level, SA patients demonstrate a paradoxical increase in both low and fast frequency bands during the performance of a mental arithmetic task, while, patients with SZ show a decreased coherence in the alpha band, presumably alluding to the excessive excitatory (in SA) and inhibitory (in SZ) mechanisms in cognitive processing. SIGNIFICANCE: The current study provides evidence for the distinction of neurophysiological mechanisms of cognitive processing between SZ and SA.

The Study of the Antisaccade Performance and Contingent Negative Variation Characteristics in First-Episode and Chronic Schizophrenia Patients.

The study tested whether the antisaccade (AS) performance and Contingent Negative Variation (CNV) measures differed between the first-episode and chronic patients to provide the evidence of PFC progressive functional deterioration. Subjects included 15 first-episode and 20 chronic schizophrenic patients (with the duration of illness more than 5 years), and 21 control subjects. The first-episode and chronic patients had significantly elevated error percent (p < .05, effect size 1.10 and p < .001, effect size 1.25), increased AS latencies (p < .01, effect size 1.18 and p < .001, effect size 1.69), and increased latencies variability (p < .01, effect size 1.52 and p < .001, effect size 1.37) compared to controls. Chronic patients had marginally significant increase of the response latency (p = .086, effect size .78) and latency variability (p < .099, effect size .63) compared to first-episode ones. Results of CNV analysis revealed that chronic patients only exhibited robustly declined frontal CNV amplitude at Fz (p < .05, effect size .70), F3 (p < .05, effect size .88), and F4 (p < .05, effect size .71) sites compared to controls. The obtained results might be related to specific changes in prefrontal cortex function over the course of schizophrenia.

Startle Modification and P50 Gating in Schizophrenia Patients and Controls: Russian Population.

Prepulse modification of the acoustic startle response (ASR) and P50 gating are potential neurophysiological endophenotypes of schizophrenia and may be used in the construction of valid clinical biomarkers. Such approach requires a large amount of data obtained in the representative samples from different gender, socio-typological and ethnic groups, replicating studies using the similar protocols and meta-analyses. This is a replication study of ASR and the first study of P50 suppression in Russian patients with schizophrenia (n = 28) and healthy controls (n = 25). ASR and P50 were estimated according to standard protocols. Patients exhibited increased baseline ASR latency (d = 0.35, p = .026) and reduced prepulse inhibition (PPI) at 60 ms interval (d = 0.39, p = .003) and 120 ms interval (d = 0.37, p = .005) relative to controls. In the P50 test patients displayed greater S2 response amplitude (d = 0.24, p = .036) and deficit of P50 suppression (d = 0.43, p = .001). No correlations of PPI and P50 suppression were found in both groups. Only in controls prepulse ASR facilitation (at 2500 ms interval) positively correlated with P50 suppression (r = -.514, p = .013). In patients PPI displayed significant correlations with Difficulty in abstract thinking (N5: r = -.49, p = .005) and Hallucination (P3: r = .40, p = .036) PANSS scales. Logistic regression showed that the combination of PPI and P50 suppression could serve as a diagnostic predictor. Obtained results demonstrated that both PPI and P50 could be regarded as potential schizophrenia biomarkers in Russian population.

The antisaccade task performance deficit and specific CNV abnormalities in patients with stereotyped paraphilia and schizophrenia.

Antisaccade task performance and mean amplitudes of slow cortical potentials (contingent negative variation--CNV) were investigated in 19 healthy volunteers, 16 schizophrenic patients (SP), and 12 patients with stereotyped form of paraphilia (PP). Compared with healthy subjects, schizophrenic and paraphilic patients committed significantly more erroneous saccades. The clear between-group CNV differences were observed during the early CNV stage that is associated with cognitive aspects of preparatory set. In SP, as compared to controls, the significant decline of CNV amplitude was found at frontal-central area. PP have demonstrated the lack of CNV over central and parietal regions, but their CNV amplitudes in frontal area did not differ from values of control group. Thus, two distinct types of CNV abnormalities have been found. The SP results have been interpreted as support for frontal dysfunction in schizophrenia. The disconnection between prefrontal cortex, sensorimotor cortex, and related subcortical structures is hypothesized in paraphilia group.

Waking EEG spectral power and coherence differences between high and low hypnotizable subjects.

EEG spectral power and coherence were analyzed under waking baseline condition in 19 high (HH) and 12 low (LH) hypnotizable subjects. In HH subjects, the theta1 and theta2 spectral power was higher than in LH. The major new finding of this study is that coherence between distributed brain regions was sharply elevated in HH subjects within the theta and alpha frequency bands. In contrast, spectral power and coherence of beta2 and gamma1 bands were higher in LH subjects as compared to HH subjects. However, the long distance coherence between frontal and posterior areas within beta-gamma frequency ranges was higher in HH subjects. It might be supposed that HH subjects are engaged in imaginal mental activity whereas LH ones are mainly engaged in linguistic activity. The neurophysiological basis of the obtained EEG differences is discussed.

The relationship between hypnotizability, internal imagery, and efficiency of neurolinguistic programming.

Subjective scoring and autonomic variables (heart rate, skin conduction span) were used to verify the reality of inner experience during recollection of emotionally neutral, positive, and negative past events in 19 high (HH) and 12 low (LH) hypnotizable subjects in hypnotic and nonhypnotic experimental sessions. Also, the influence of hypnotizability on the effectiveness of an imagery-based neurolinguistic programming (NLP) technique was evaluated. Results demonstrated that subjective scores of image vividness and emotional intensity were significantly higher in the HH subjects compared to LH in both sessions. The past-events recollection was followed by increased autonomic activity only in the HH subjects. The NLP procedure was followed by decreased negative emotional intensity in both groups, but autonomic activity decline was observed in the HH subjects and not in the LH.

Startle modification and P50 gating in schizophrenia patients and controls: Russian population

Prepulse modification of the acoustic startle response (ASR) and P50 gating are potential neurophysiological endophenotypes of schizophrenia and may be used in the construction of valid clinical biomarkers. Such approach requires a large amount of data obtained in the representative samples from different gender, socio-typological and ethnic groups, replicating studies using the similar protocols and meta-analyses. This is a replication study of ASR and the first study of P50 suppression in Russian patients with schizophrenia (n = 28) and healthy controls (n = 25). ASR and P50 were estimated according to standard protocols. Patients exhibited increased baseline ASR latency (d = 0.35, p = .026) and reduced prepulse inhibition (PPI) at 60 ms interval (d = 0.39, p = .003) and 120 ms interval (d = 0.37, p = .005) relative to controls. In the P50 test patients displayed greater S2 response amplitude (d = 0.24, p = .036) and deficit of P50 suppression (d = 0.43, p = .001). No correlations of PPI and P50 suppression were found in both groups. Only in controls prepulse ASR facilitation (at 2500 ms interval) positively correlated with P50 suppression (r = -.514, p = .013). In patients PPI displayed significant correlations with Difficulty in abstract thinking (N5: r = -.49, p = .005) and Hallucination (P3: r = .40, p = .036) PANSS scales. Logistic regression showed that the combination of PPI and P50 suppression could serve as a diagnostic predictor. Obtained results demonstrated that both PPI and P50 could be regarded as potential schizophrenia biomarkers in Russian population (AU)

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The contingent negative variation laterality and dynamics in antisaccade task in normal and unmedicated schizophrenic subjects

Contingent negative variation (CNV) topography, hemispheric asymmetry and time-course were investigated in healthy subjects and non-medicated paranoid schizophrenic patients in two antisaccade paradigms with the short (800-1000 ms) and long (1200-1400 ms) durations of the fixation period. EEG and electrooculogram (EOG) were recorded. Saccade characteristics and mean amplitudes ofslow cortical potentials time-locked to peripheral target were analyzed in 23 healthy volunteers and 19 schizophrenic patients. Compared to healthy control subjects, schizophrenic patients had significantly slower antisaccades and committed significantly more erroneous saccades in the both antisaccade tasks. The prolongation of the fixation period resulted in noticeable decrease of error percent in patients group. The analysis of CNV time-course has revealed two distinct stages in both groups. The early CNV stage was represented by a negative wave with the maximal amplitude over midline fronto-central area, and the late stage was characterized by increased CNV amplitude at the midline and left parietal electrode sites. In healthy subjects the simultaneous activation of frontal and parietal areas was observed in the paradigm with the shorter fixation interval; the increase of the fixation period produced consecutive activation of these areas. Schizophrenic patients’ CNV amplitude was generally smaller than that of healthy subjects. The most pronounced between-group differences of the negative shift amplitude were revealed at frontal electrode sites during the early CNV stage in both modifications of the antisaccade task. The deficit of frontal activation revealed in patients at the early stage of antisaccade preparatory set in both antisaccadic paradigms may be related to pathogenesis of paranoid schizophrenia (AU)

Se ha investigado la topografía de la variación contingente negativa (CNV), su curso temporal, y asimetría hemisférica en sujetos normales y en pacientes esquizofrénicos paranoides no medicados durante dos paradigmas de movimientos antisacádicos con duración corta (800-1000 ms) y larga (1200-1400 ms) del periodo de fijación. Se registraron el EEG y electro-oculograma. Las características de los movimientos sacádicos y las amplitudes medias de los potenciales corticales lentos relacionados a objetivos periféricos se analizaron en 23 voluntarios sanos y 19 pacientes esquizofrénicos. Comparados con el grupo sano control, los pacientes esquizofrénicos tuvieron movimientos antisacádicos significativamente más lentos y cometieron significativamente más movimientos sacádicos erróneos en ambas tareas antisacádicas. La prolongación del periodo de fijación resultó en un decremento notable del porcentaje de errores en el grupo de pacientes. El análisis del curso temporal de la CNV ha revelado dos etapas distintas en ambos grupos. La etapa temprana de la CNV estuvo representada por una onda negativa con amplitudes máximas en regiones fronto-centrales de la línea media y la etapa tardía estuvo caracterizada por un incremento de la amplitud de la CNV en electrodos parietales izquierdos y de la línea media. En sujetos sanos se observó activación simultánea de áreas parietales y frontales durante el paradigma de intervalo de fijación corto; el incremento del periodo de fijación produjo activación consecutiva de estas áreas. La amplitud de la CNV de pacientes esquizofrénicos fue generalmente menor que la de los sujetos sanos. Las diferencias más pronunciadas entre-grupos en la amplitud de la deflección negativa fueron evidentes en electrodos frontales durante la etapa temprana de la CNV en ambas modificaciones de la tarea antisacádica. El déficit de la activación frontal demostrado en pacientes durante el estado temprano de la preparación antisacádica en ambos paradigmas puede estar relacionado con la patogénesis de la esquizofrenia paranoide (AU)