Nonlinear dynamics of electroencephalography study in schizophrenic patients.

BACKGROUND: Few characteristic changes of linear electroencephalograph (EEG) have been reported in schizophrenia. The aim of the present study was to investigate the changes in temporal-spatial dimensional properties of EEG under different cognitive tasks in patients with schizophrenia. METHODS: EEG was recorded by using EEG-1518K system and mapping system (Nihon Kohden Tomioka Corporation, Japan) in 45 schizophrenic patients and 47 healthy adults (normal control, NC) under five states: eyes closed, eyes open, mental arithmetic test with eyes closed, memory test with eyes open, and number cancellation test. Correlation dimension (D2) and point-wise correlation dimension (PD2) were calculated for all EEG analyses. RESULTS: (1) There were no significant differences of D2 and PD2 between NC and schizophrenic patients under states of eyes open and closed. (2) Compared with NC, schizophrenic patients showed decreased performance of D2 in mental arithmetic test with eyes closed and number cancellation test (mental arithmetic test with eyes closed: Nc 5.9 ± 0.6, Sch 3.0 ± 0.8; number cancellation test: Nc 6.0 ± 0.6, Sch 4.4 ± 0.7; P < 0.05 or P < 0.01). (3) Schizophrenic patients also showed decrease performance of PD2 in mental arithmetic test with eyes closed, memory test with eyes open, and number cancellation test (mental arithmetic test with eyes closed: Nc 6.9 ± 0.7, Sch 4.0 ± 0.8; memory test with eyes open: Nc 6.6 ± 0.8, Sch 5.0 ± 0.9; number cancellation test: Nc 7.1 ± 0.7, Sch 4.8 ± 0.9; P < 0.05 or P < 0.01). CONCLUSIONS: Nonlinear dynamic analysis provided a new approach in clinical investigation of EEG signals. It was helpful to further understand the cerebral mechanism in schizophrenic cognitive process.

Neonatal ventral hippocampal lesion as a valid model of schizophrenia: evidence from sensory gating study.

BACKGROUND: The neonatal ventral hippocampal lesion (NVHL) rat model has been proposed as an experimental model for schizophrenia. NVHL rats display impaired central nervous system (CNS) inhibition, which may lead to a phenomenon similar to P50 sensory gating deficits observed in schizophrenic patients. In this study, we investigated whether sensory gating deficits occurred in the NVHL rat as a model for schizophrenia. METHODS: We created the NVHL rat model using ibotenate. The P20 and N40 were measured to assess sensory response and gating in NVHL and sham rats. Epidural electrodes recorded evoked potentials (EPs), from which latencies, amplitudes, difference scores (S1-S2), and gating ratios (S2/S1) were assessed. RESULTS: Compared with sham controls, prolonged S1 N40 latency and decreased S2 N40 amplitude were detected in the NVHL group. In neither difference scores nor gating ratios, a significant difference was found between NVHL group and sham controls. CONCLUSIONS: NVHL rats may be a valid animal model for schizophrenia. This strategy will be useful in future neurobiological studies investigating the etiology of schizophrenia.

[Preliminary study on variations and neural generators of error-related negativity in first episode schizophrenics].

OBJECTIVE: To explore the variations and their activated brain areas of error-related negativity (ERN) in first episode schizophrenics. METHODS: ERN was tested by an ERP device and their activated brain areas were compared in 58 first episode schizophrenics (FES) and 62 normal controls (NC) from March 2010 to February 2011. RESULTS: (1) The ERN latencies in the FES group were significantly longer on Cz (58 ± 14 ms), Fz (60 ± 11 ms), C3 (57 ± 17 ms) and C4 (60 ± 13 ms) electrodes compared with those in the NC group (49 ± 13 ms, 47 ± 13 ms, 50 ± 14 ms, 51 ± 12 ms). And the ERN amplitudes were significantly lower than those in the controls in Cz (5.0 ± 2.8 µV; 7.5 ± 3.1 µV, P < 0.01), C3 (5.5 ± 4.0 µV; 8.0 ± 3.7 µV, P < 0.01), Fz (5.0 ± 3.1 µV; 7.7 ± 3.8 µV, P < 0.01) and Pz (4.5 ± 3.3 µV: 7.5 ± 3.0 µV, P < 0.01) electrodes.(2) The variations of ERN latencies and amplitudes showed an insignificant correlation with the positive symptom scores and total scores of PANSS. (3) The activation levels of insula, superior temporal gyrus, middle temporal gyrus and inferior parietal lobule were obviously lower in the FES group than those in the NC group. CONCLUSION: The anomalies of ERN latencies and amplitudes in first episode schizophrenics may reflect the deficient error-monitoring functions. Further studies are warranted. And such brain areas as insular may contribute pathogenically to the dysfunctions of error-monitoring in schizophrenics.

[N400 changes elicited by Chinese sentences in first episode schizophrenia].

OBJECTIVE: To explore N400 changes elicited by Chinese sentences ending with matching (congruent) or mismatching (incongruent) words in first episode schizophrenia. METHODS: ERP (event-related potentials) component N400 were recorded by an ERP device in 56 first episode schizophrenia (FES) and 62 normal controls (NC) according to a paradigm of Chinese sentences ending with matching or mismatching words. RESULTS: (1) Latencies: compared with NC, FES showed prolonged N400 latencies in five areas at pre-treatment: in Cz. The latencies were (358 ms ± 32 ms vs 394 ms ± 45 ms, P < 0.01) in congruent and (410 ms ± 29 ms vs 446 ms ± 35 ms, P < 0.01) in incongruent situation. And so did in Fz, Pz, C3 and C4; (2) amplitudes: compared with NC, FES also showed smaller N400 amplitudes in five areas at pre-treatment. The amplitudes were (8.6 µV ± 5.1 µV vs 5.2 µV ± 4.6 µV, P < 0.01) in congruent and (13.4 µV ± 6.7 µV vs 8.5 µV ± 5.9 µV, P < 0.01) in incongruent situation. And so did in Fz, Pz, C3 and C4; (3) the prolonged N400 latencies and decreased amplitudes were negatively correlated with the patients' positive scale and total scale of PANSS. CONCLUSION: With clear priming effect in first episode schizophrenia, Chinese sentences are suitable stimuli in N400 experiment. They may be used for further study of neural mechanism and early diagnosis of schizophrenia.

[The follow-up study on P50 auditory sensory gating in naïve schizophrenia].

OBJECTIVE: To understand the variations of sensory gating P50 in naïve schizophrenia during follow-up and the relations with positive and negative symptom scale (PANSS). METHODS: The data of auditory evoked potential P50 were recorded by USA Nicolet Brova instrument from 58 naïve schizophrenia patients (Sch) and 108 normal controls (NC) at baseline, Months 1, 2 and 3 after treatment. And a simultaneous assessment of PANSS was made. RESULTS: (1) At baseline, as compared with NC, Sch group had a sensory gating deficit, reflected by a higher S2/S1 (Cz: NC: 0.43 (0.27, 0.58); Sch: 0.77 (0.58, 1.04); Z = -9.23, P < 0.01), lower S1-S2 (Cz: NC: 2.65 (1.55, 4.79) microV; Sch: 0.92(-0.13, 2.32) microV; Z = -6.01, P < 0.01) and decreased more (1-S2/S1) (Cz: NC: 0.57 (0.43, 0.73); Sch: 0.23 (-0.04, 0.42); Z = -10.61, P < 0.01). (2) During follow-up, Sch group still had a sensory gating deficit. Compared with NC, Sch group had a more elevated S2-P50 amplitude, higher S2/S1, lower S1-S2 and (1-S2/S1) at Cz, Fz and Pz brain sites (P < 0.05 - 0.01), and no significantly differences with S2-P50 amplitude, S2/S1, S1-S2 and (1-S2/S1) during follow-up (P > 0.05). At baseline, Sch group had a much lowered S1-P50 amplitude than NC group at Cz and Fz brain sites (Cz: Sch: 4.1 microV +/- 2.1 microV, NC: 5.6 microV +/- 3.3 microV, t = -1.47, P = 0.001; Fz: Sch: 3.9 microV +/- 2.1 microV, NC: 5.6 microV +/- 3.9 microV, t = -1.63, P = 0.003). At Month 3, Sch group showed an improved S1-P50 amplitude to normal level at Cz brain site, but S1-P50 amplitude improved at Fz brain site but it was lower than NC group (Sch: 3.9 microV +/- 1.9 microV, NC: 5.6 microV +/- 3.9 microV, t = -1.62, P = 0.03). (3) At Month 3, Sch group showed a much lowered PANSS scale, positive symptom scale, negative symptom scale and general psychiatric symptoms scale than that at baseline (baseline: 138 +/- 15, 33 +/- 7, 41 +/- 5, 65 +/- 8; Month 3: 80 +/- 15, 17 +/- 4, 24 +/- 4, 38 +/- 9 respectively, P < 0.01). Spearman correlation revealed that P50 was not correlated with PANSS at baseline (P > 0.05). After treatment S2/S1 and (1-S2/S1) correlated with positive symptom scale and thought disorder and S1-S2 positively with thought disorder in schizophrenia (P < 0.05). CONCLUSION: Sensory gating deficit is closely related with thought disorder in naïve schizophrenia. And it may be an important pathogenesis of naïve schizophrenia. P50 sensory gating deficit is probably a diathesis marker in schizophrenia.

[Experimental study on sensory gating in generalized anxiety and obsessive compulsive disorders].

OBJECTIVE: To observe the characteristics of sensory gating P50 in generalized anxiety disorder (GAD) and in obsessive compulsive disorder (OCD) patients. METHODS: Auditory evoked potentials P50 were recorded in 41 GAD patients, 69 OCD patients and in 58 normal controls by the conditioning/testing paradigm presented with auditory double clicks stimuli, using American Nicolet Bravo instrument. RESULTS: (1) No significant differences was found in latencies of S1-P50 and S2-P50 among these three groups (P > 0.05). (2) Significant differences were found in indices of S1-P50 amplitudes (NC: 6 +/- 3, GAD: 3 +/- 2, OCD: 5 +/- 3, P < 0.01), S2-P50 amplitudes (NC: 2 +/- 1, GAD: 4 +/- 1, OCD: 2 +/- 1, P < 0.01), S2/S1, S1-S2 and 100(1-S2/S1). (3) Compared with NC, GAD and OCD patients showed a decreased S1-P50 amplitude and OCD patients also showed an increased S2-P50 amplitude. (4) P50 inhibition significantly decreased in GAD and OCD patients. The values of S2/S1 ratio were 39% +/- 22% in NC, 50% +/- 29% in GAD and 88% +/- 42% in OCD (P < 0.01). (5) Both S1-S2 and 100 (1-S2/S1) decreased in GAD and OCD patients (NC: 3 +/- 2, 61 +/- 22; OCD: 1 +/- 1, 15 +/- 22; GAD: 3 +/- 3, 50 +/- 29. P < 0.01). (6) Compared with GAD, OCD patients showed a lower S2/S1 ratio (P < 0.01) and a higher value of S1-S2 (P < 0.01) and 100 (1-S2/S1) (P < 0.01). CONCLUSION: The anxiety disorder patients has sensory gating deficits. The inhibition deficit can be measured by auditory evoked potential P50. And S2/S1 ratio, S1-S2 and 100(1-S2/S1) may be biological markers of GAD and OCD patients.

N400 elicited by incongruent ending words of Chinese idioms in healthy adults.

BACKGROUND: Prior research about N400 has been mainly based on English stimuli, while the cognitive processing of Chinese characters is still unclear. The aim of the present study was to further investigate the semantic processing of Chinese idioms. METHODS: Event related potentials (ERP) component N400 was elicited by 38 pairs of matching (congruent) and mismatching (incongruent) ended Chinese idioms: ending words with same phoneme but different shape and meaning (sPdSdM), with similar shape but different phoneme and meaning (sSdPdM), with same meaning but different phoneme and shape (sMdPdS), and words with different phoneme, shape and meaning (dPdSdM) and recorded by Guangzhou Runjie WJ-1 ERP instruments. In 62 right-handed healthy adults (age 19 - 50 years), N400 amplitudes and latencies were compared between matching and mismatching conditions at Fz, Cz and Pz. RESULTS: N400 showed a midline distribution and could be elicited in electrodes Fz, Cz and Pz. The mean values of N400 latencies and amplitudes were obtained for matching and mismatching ending words in healthy adults. Significant differences were found in N400 latencies and amplitudes in matching and mismatching ending-words idioms in healthy adults (P < 0.05). Compared with matching ending-words idioms, N400 latencies were prolonged and the amplitudes were increased in mismatching ones. N400s elicited by different types of stimuli showed different latencies and amplitudes, and longest N400 latency and largest N400 amplitude were elicited by ending-words with dPdSdM. No gender difference was found of N400 latency and amplitude in this study (P > 0.05). CONCLUSIONS: Compared with English stimuli, Chinese ideographic words could provide more flexible stimuli for N400 research in that the words have 3-dimension changes - phoneme, shape and meaning. Features of N400 elicited by matching and mismatching ending words in Chinese idioms are mainly determined by the meaning of the word. Some issues of N400 elicited by Chinese characters deserve further research.

[Effects of risperidone on polysomnography in patients with first-episode schizophrenia].

OBJECTIVE: To investigate the effects of risperidone on the polysomnography (PSG) in the patients with first-episode schizophrenia. METHODS: Twenty-five patients with first-episode schizophrenia, 13 males and 12 females, aged 29 +/- 8, underwent polysomnographic recording for 4 consecutive nights, the first night being used for acclimatization, and on the 3 rd and 4 th nights risperidone in the dose of 1.2 mg was administered before going to bed. Forty-four healthy persons, 23 males and 21 females, aged 28 +/- 8, underwent polysomnographic recording for 2 consecutive nights, the first night being used for acclimatization. RESULTS: The baseline PSG recording showed that in comparison with the normal control group the total sleep time of the schizophrenia patients was shorter (378 min +/- 30 min vs 462 min +/- 21 min), sleep latency was longer (30 min +/- 14 min vs 18 min +/- 8 min), rapid eye movement (REM) sleep latency was shorter (59 min +/- 20 min vs 88 min +/- 10 min), REM sleep time was shorter (61 min +/- 17 min vs 84 min +/- 12 min), awakening time was longer (34 min +/- 17 min vs 15 min +/- 5 min), stage 1 (S1) time was longer (22% +/- 10% vs 9.0% +/- 1.7%), S3 time and S4 time were shorter, and the sleep efficacy was lower (86% +/- 10%) (P < 0.05 approximately P < 0.01); however, there was no significant difference in the S2 time between these 2 groups (54% +/- 16% vs 56% +/- 4%, P > 0.05). In the schizophrenia group, in comparison with the baseline levels in the third and fourth nights the total sleep times were significantly increased (406 min +/- 34 min and 428 min +/- 31 min respectively), the awakening times were significantly decreased (23 min +/- 15 min and 19 min +/- 8 min respectively), and S1 times were significantly decreased (14 min +/- 9 min and 10 min +/- 9 min respectively), with such changes time-dependently; and in the 4 th night the REM sleep time was significantly increased (87 min +/- 20 min) and the sleep efficacy was significantly improved (93% +/- 12%) (P < 0.05 approximately P < 0.01), however, there were no significant differences in the sleep latency and slow wave sleep (both P > 0.05). CONCLUSION: Risperidone significantly improves the quality of sleep.