Contributions of spectral frequency analyses to the study of P50 ERP amplitude and suppression in bipolar disorder with or without a history of psychosis

Objective: The present study investigated event-related brain potential (ERP) indices of auditory processing and sensory gating in bipolar disorder and subgroups of bipolar patients with or without a history of psychosis using the P50 dual-click procedure. Auditory-evoked activity in two discrete frequency bands also was explored to distinguish between sensory registration and selective attention deficits. Methods: Thirty-one individuals with bipolar disorder and 28 non-psychiatric controls were compared on ERP indices of auditory processing using a dual-click procedure. In addition to conventional P50 ERP peak-picking techniques, quantitative frequency analyses were applied to the ERP data to isolate stages of information processing associated with sensory registration (20–50 Hz; gamma band) and selective attention (0–20 Hz; low-frequency band). Results: Compared to the non-psychiatric control group, patients with bipolar disorder exhibited reduced S1 response magnitudes for the conventional P50 peak-picking and low-frequency response analyses. A bipolar subgroup effect suggested that the attenuated S1 magnitudes from the P50 peak-picking and low-frequency analyses were largely attributable to patients without a history of psychosis. Conclusions: The analysis of distinct frequency bands of the auditory-evoked response elicited during the dual-click procedure allowed further specification of the nature of auditory sensory processing and gating deficits in bipolar disorder with or without a history of psychosis. The observed S1 effects in the low-frequency band suggest selective attention deficits in bipolar patients, especially those patients without a history of psychosis, which may reflect a diminished capacity to selectively attend to salient stimuli as opposed to impairments of inhibitory sensory processes.     

Alterations in tonotopy and auditory cerebral asymmetry in schizophrenia.

BACKGROUND: Deficits in basic auditory perception have been described in schizophrenia. Previous electrophysiologic imaging research has documented a structure-function disassociation in the auditory system in schizophrenia. This study examines whether the most fundamental level of auditory cortical organization, tonotopy, is altered in schizophrenia. METHODS: The tonotopic organization for five tone frequencies in 19 patients with schizophrenia and 22 comparison subjects was evaluated using magnetoencephalography. Auditory evoked magnetic field dipole locations were examined for the N100m component for each frequency. RESULTS: The expected linear relationship between depth and frequency was found in the comparison subjects but not in the schizophrenia group (p <.004). In addition, normal anterior-posterior asymmetry of the N100m was found to be reduced at all five stimulation frequencies employed in the study (p <.04). No relationships between clinical symptom ratings and either tonotopy or asymmetry were observed. CONCLUSIONS: This finding suggests that the tonotopic organization of the auditory cortex in schizophrenia is disturbed and may help explain the relatively poor behavioral performance of schizophrenia patients on simple frequency discrimination tasks. Alterations in fundamental sensory organization may underlie or interact with higher order cognitive mechanisms to produce changes in cognitive task performance.     

Evoked potentials in hereditary spastic paraplegia

Pattern reversal visual evoked response (VER) and monaural stimulation of brainstem auditory evoked responses (BAER) were recorded from both sides in 25 patients (males 19; females 6) with hereditary spastic paraplegia (HSP). Their age ranged from 15–52 (mean±SD; 25.2±22.5) years and duration of symptoms 6 months-9 (mean±SD; 4.2±3.6) years. A prolonged P 100 latency was seen in 6 patients and BAER abnormality in 13. None of the patients had clinical evidence of brainstem involvement. It is suggested that VER and BAER abnormalities are due to segmental demyelination and fiber loss in central conduction pathways and could serve as an important tool for the diagnosis of this disorder.

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Sommario I potenziali evocati visivi (VER) e uditivi del tronco (BAER) sono stati registrati bilateralmente in 25 pazienti (19 maschi e 6 femmine) affetti da paraplegia spastica ereditaria (HSP). La loro età media era compresa tra 15 e 52 anni (media±DS=25.2±22.5) e con una durata di malattia compresa tra 6 mesi e 9 anni (media±DS=4.2±3.6). In 6 pazienti è stato riscontrato un aumento della latenza della P100 e in 13 i BAER erano anormali. Nessuno dei pazienti presentava segni clinici di coinvolgimento del tronco. Viene ipotizzato che le anormalità osservate ai VER e BAER sono dovute ad una demielinizzazione segmentaria o a perdita di fibre lungo le vie di conduzione cerebrale. Questi esami strumentali sarebbero quindi di grande utilità nella diagnosi di HSP.

     

Neurophysiological study in chronic GM2 gangliosidosis (hexosaminidase A and B deficiency), with motor neuron disease phenotype

We report the electrophysiological investigation of two adult cases with GM 2 gangliosidosis with hexosaminidase A and B deficiency. Superficial peroneal biopsy was obtained from one patient. The electrophysiological alterations of the peripheral nervous system were fasciculations, signs of collateral reinnervation and loss of motor units, decrease in sensory potential amplitude and increase in distal motor latency. Increase in N9-N13 interpeak latency of the somatosensory evoked potentials and an increase I–V interpeak latency of the brain-stem auditory potentials were evident in both cases. Visual evoked potentials were normal. Nerve biopsy showed a severe loss of myelinated fibers, especially of those with the largest diameter, with no signs of segmental demyelination, or remyelination. A tentative interpretation of our findings is given.

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Sommario Gli autori riportano lo studio neurofisiologico ed istologico di 2 soggetti adulti affetti da GM2 gangliosidosi da deficit di esosaminidasi A e B. Le alterazioni elettrofisiologiche del sistema nervoso periferico consistono in fascicolazioni, segni di reinnervazione collaterale e perdita di unità motorie, riduzione in ampiezza dei potenziali sensitivi e incremento delle latenze motorie distali. Sono presenti in ambedue i casi un incremento dell'interpicco N9-N13 dei potenziali evocati somatosensoriali e un aumento dell'interlatenza I–V di quelli uditivi. Normali sono i potenziali evocati visivi. La biopsia del nervo peroneo superficiale eseguita in un solo soggetto dimostra una severa perdita di fibre mieliniche soprattutto di più grosso calibro, senza segni di demielinizzazione segmentaria o rimielinizzazione. Viene infine proposta un 'interpretazione di tutti i dati.

     

Brainstem auditory-evoked responses and clinical picture in a one year follow-up of 18 patients with Friedreich ataxia

Brainstem auditory-evoked responses (BAER) and behavior audiometry were evaluated on 18 patients with Friedreich ataxia. Behavior audiometry showed a normal pure tone test, normal performance intensity and phonetically balanced functions in all patients. BAER were abnormal in all patients. The data obtained show a good correlation between BAER and clinical picture and suggest that BAER could be useful in monitoring the clinical condition of FA patients.

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Sommario In 18 pazienti con atassia spinocerebellare di Friedreich sono stati valutati i potenziali evocati acustici del tronco (PEAT) e le audiometrie comportamentale. L'audiometria comportamentale ha dimostrato in tutti i pazienti: a) normale test audiometrico tonale liminare; b) normale risposta per la intensità di stimolo usata; c) normale risposta al test delle parole foneticamente bilanciate. I PEAT sono risultati peraltro anormali in tutti i pazienti. I dati ottenuti sono in favore di una correlazione positiva tra stadio clinico della malattia e grado di alterazione dei PEAT, suggerendo che i PEAT possono essere utilizzati nel monitoraggio della condizione clinica dei pazienti con atassia di Friedreich.

     

Clinical correlates of abnormal brain-stem auditory evoked responses in multiple sclerosis

Brain-stem auditory evoked responses (BAERs) were examined in 178 patients with multiple sclerosis (MS) and compared to the frequency of abnormalities in visually evoked responses (VERs) and in CSF electrophoresis. In clinically definite MS, BAERs were abnormal in 61% and a significant relationship was noted between disability due to MS and the frequency and severity of BAER abnormalities. In suspected MS, BAERs showed evidence of a second lesion in 14% whereas VERs indicated a second lesion in 24%. Abnormal BAERs in patients with suspected MS with brain-stem signs were significantly associated with the presence of truncal and limb ataxia. In progressive possible MS, abnormal BAERs were found in 49% but indicated a second lesion in 35% of patients and were significantly related to the duration of illness. In progressive possible MS, abnormal VERs but not abnormal BAERs, were significantly associated with the presence of CSF oligoclonal IgG banding. Normal BAERs in association with clinical brain-stem abnormalities were found in 24% of patients with clinically definite MS, 50% with suspected MS and 33% with progressive possible MS.     

Lithium alters measures of auditory gating in two strains of mice.

BACKGROUND: There are similarities between schizophrenia and bipolar disorder, especially during the psychotic phase. Auditory gating deficits are common in both schizophrenia (does not remit postpsychotic event) and bipolar disorder (only during the manic phase). Lithium has been used to treat psychosis acutely in both bipolar disorder and schizophrenia. An animal model was used to assess the effects of lithium treatment on normal and deficient auditory gating. METHODS: Mice of the DBA/2 (deficient gating) and C3H (normal gating) strains were treated for 6 weeks with either standard rodent chow or rodent chow supplemented with 2.55g/kg lithium carbonate. After 6 weeks of treatment, auditory evoked potentials were recorded under anesthesia. Differences between the groups and treatments were determined using analysis of variance. RESULTS: The normally impaired DBA/2 mice showed improved auditory gating following lithium treatment, while the C3H mice, the benchmark "normal" mouse strain, were impaired after lithium treatment. CONCLUSIONS: C3H mice treated with lithium had significantly impaired auditory gating as a result of treatment. This may be due to norepinephrine facilitation, through a blockade of presynaptic alpha(2) autoreceptors. DBA/2 mice had improved gating as a result of treatment with lithium, likely due to improved functioning of the gamma-aminobutyric acid system.     

婴儿痉挛症脑干听觉诱发电位中的γ频带

目的 观察婴儿痉挛症患者脑干听觉诱发电位中γ频带成分。方法 用子波变换分别对正常婴儿、婴儿痉挛症患儿、经过一段时间治疗后的婴儿痉挛症患儿脑干听觉诱发电位信号进行多尺度分析。观察脑干听觉诱发电位信号多尺度成分的分尺度功率随尺度的分布。结果 婴儿痉挛症患儿的脑干听觉诱发电位信号的γ频带的成分缺损严重，其分尺度功率远低于正常婴儿，婴儿痉挛症患儿经过一段时间治疗后脑干听觉诱发电位信号的γ频带成分明显改善，其分尺度功率接近正常婴儿。结论 γ频带对信启在脑干中的接收、传输、加工、综合、反馈等高级功能和人脑的认知活动具有重要作用，γ频带成分缺损导致的信息传导阻滞是引起患儿智能发育迟滞的原因。     

Auditory evoked potentials and magnetic fields in patients with lesions of the auditory cortex

Auditory evoked potentials and magnetic fields of 40-200 ms latencies were measured from 4 patients with temporal lobe infarcts and compared with results from healthy subjects. Magnetic fields over the diseased hemisphere were abnormal in all 4; the responses were missing in 2. In one patient the responses were of abnormally high amplitude, and in one parts of the response sequence were missing. Evoked potentials were also abnormal in all 4 patients and the results were in accordance with the findings in the magnetic field measurements.     

Visual and brain stem auditory evoked responses in Wilson''s disease

Sensory evoked potentials were studied in 15 patients with Wilson's disease. Thirteen patients were investigated with pattern reversal visual stimulation. A prolonged P 100 latency of the VEP was present in 7 patients. Brain stem auditory responses were evoked in 12 patients. Prolongation of III-V and I-V interpeak latency was found in 8 patients. The evoked potential studies demonstrated subclinical disturbances in optic and caudal brainstem auditory pathways. Further studies are in progress to evaluate the role of these techniques in monitoring the therapy of newly diagnosed cases.     

抑郁首次发作患者感觉门控P50的研究

目的研究抑郁首次发作(以下简称首发)患者的感觉门控P50特点。方法对39例符合国际疾病分类第10版抑郁发作诊断标准的首次抑郁发作患者(患者组)采用17项汉密尔顿抑郁量表(HAMD17)评定病情严重程度,并进行感觉门控P50检测,与40名健康志愿者(对照组)进行比较。结果(1)患者组P50测试刺激波(S2-P50)的波幅[(2.30±1.04)μV]低于条件刺激波(S1-P50)波幅[(3.48±1.66)μV],但高于对照组S2-P50波幅[(1.54±1.26)μV;P<0.01];患者组的S2/S1波幅比值[(70±23)%]高于对照组[(42±26)%;P<0.01],而S1-S2波幅绝对差值[(1.19±1.48)μV]却低于对照组[(2.17±2.16)μV;P<0.05];患者组P50抑制度[(29±23)%]也低于对照组[(57±26)%;P<0.01]。(2)经Pearson相关分析,患者组HAMD17量表评分与P50各指标无相关(P>0.05)。结论抑郁症首发患者感觉门控抑制存在明显缺损,不能有效滤过无关信息。     

Habituation of visual evoked responses in neonates and fetuses: a MEG study

In this study we aimed to develop a habituation paradigm that allows the investigation of response decrement and response recovery and examine its applicability for measuring the habituation of the visually evoked responses (VERs) in neonatal and fetal magnetoencephalographic recordings. Two paradigms, one with a long and one with a short inter-train interval (ITI), were developed and tested in separate studies. Both paradigms consisted of a train of four light flashes; each train being followed by a 500Hz burst tone. Healthy pregnant women underwent two prenatal measurements and returned with their babies for a neonatal investigation. The amplitudes of the neonatal VERs in the long-ITI condition showed within-train response decrement. An increased response to the auditory dishabituator was found confirming response recovery. In the short-ITI condition, neonatal amplitude decrement could not be demonstrated while response recovery was present. In both ITI conditions, the response rate of the cortical responses was much lower in the fetuses than in the neonates. Fetal VERs in the long-ITI condition indicate amplitude decline from the first to the second flash with no further decrease. The long-ITI paradigm might be useful to investigate habituation of the VERs in neonates and fetuses, although the latter requires precaution.     

The thalamic reticular nucleus and schizophrenia

Background: The thalamic reticular nucleus (TRN) is a shell-shaped gamma amino butyric acid (GABA)ergic nucleus, which is uniquely placed between the thalamus and the cortex, because it receives excitatory afferents from both cortical and thalamic neurons and sends inhibitory projections to all nuclei of the dorsal thalamus. Method: A review of the evidence suggesting that the TRN is implicated in the neurobiology of schizophrenia. Results: TRN-thalamus circuits are implicated in bottom-up as well as top-down processing. TRN projections to nonspecific nuclei of the dorsal thalamus mediate top-down processes, including attentional modulation, which are initiated by cortical afferents to the TRN. TRN-thalamus circuits are also involved in bottom-up activities, including sensory gating and the transfer to the cortex of sleep spindles. Intriguingly, deficits in attention and sensory gating have been consistently found in schizophrenics, including first-break and chronic patients. Furthermore, high-density electroencephalographic studies have revealed a marked reduction in sleep spindles in schizophrenics. Conclusion: On the basis of our current knowledge on the molecular and anatomo-functional properties of the TRN, we suggest that this thalamic GABAergic nucleus may be involved in the neurobiology of schizophrenia.     

首发强迫症感觉门控变异及与临床症状的相关性

目的:了解首发强迫症(OCD)患者的听觉P50变异特点,探讨感觉门控抑制与强迫症状的关系。方法:应用美国Nicolet Bravo脑诱发电位仪,采用听觉条件刺激(S1)-测试刺激(S2)模式对42例OCD患者和46名正常志愿者进行听觉P50检测;应用Yale-Brown强迫量表进行临床症状评定。结果:与正常组相比,强迫症组S2-P50波幅升高(P<0.05),S1-S2和100(1-S2/S1)均降低,差异有统计学意义(P均<0.01)。经Pearson相关分析,Yale-Brown强迫量表评分强迫思维因子分与S2-P50波幅呈正相关(P<0.05),与100(1-S2/S1)呈负相关(P<0.05)。结论:首发强迫症患者的感觉门控变异特点为抑制不足,强迫思维与感觉门控抑制程度有一定的相关性。     

Hypofunctioning of sensory gating mechanisms in patients with obsessive-compulsive disorder.

BACKGROUND: In obsessive-compulsive disorder (OCD) patients, functional abnormalities in basal ganglia/precentral circuitries cause cortical hyperexcitability and lack of inhibitory control. These loops can be partly explored by median-nerve somatosensory evoked potentials (SEPs), which functionally reflect the brain responsiveness to somatosensory stimuli. In healthy humans, SEPs' amplitude during voluntary finger movements is lower than during muscular relaxation (i.e., sensory gating). Cortical hyperexcitability in OCD could be eventually responsible for a reduction of sensory gating. This might have pathophysiologic implications for motor compulsions. METHODS: Median-nerve SEPs were recorded in 11 OCD patients and 9 healthy volunteers during muscle relaxation ("Relax") or finger movements of the stimulated hand ("Move"). Latencies and amplitudes of pre- and postcentral SEP components were compared between groups during "Relax" and "Move" conditions. RESULTS: In OCD patients, the responsiveness to sensory stimuli was enhanced for precentral SEPs. Sensory gating ("Relax" vs. "Move") in control subjects involved both pre- and postcentral SEPs, the former being reduced in amplitude by approximately 60%. In OCD patients, sensory gating was spatially restricted to precentral SEP components and was significantly reduced compared with control subjects (approximately 30%). CONCLUSIONS: Enhanced precentral SEPs and hypofunctioning of centrifugal sensory gating in OCD might reflect the inability to modulate sensory information due to a "tonic" high level of cortical excitability of motor and related areas, likely resulting from basal ganglia dysfunction. This might offer new insights into the pathophysiology of OCD.     

30名健康儿童的感觉门控P50研究

目的 应用诱发电位新技术探讨健康儿童感觉门控 (SG) P50特点.方法 应用美国Nicolet脑电生理仪,采用条件刺激(S1)-测试刺激(S2)模式对30名健康儿童进行听觉P50检测.结果 健康儿童Cz脑区S1-P50潜伏期(60.7±11.9)ms,波幅(5.7±3.3)μV;S2-P50潜伏期(65.4±22.0)ms,波幅(2.4±1.3)μV.S2-P50波幅显著低于S1-P50(P<0.01).S2/S1比值为(42.8±21.0)%;S1-S2波幅和100(1-S2/S1)波幅分别为(3.3±2.6)μV和(57.9±21.0)μV.结论 听觉P50电位具有抑制性特征,其变化可反映大脑健康儿童SG的功能状态.