Transcranial direct current stimulation of prefrontal cortex: An auditory event-related potential and proton magnetic resonance spectroscopy study

Transcranial direct current stimulation (tDCS) is a non-invasive intervention altering neural plasticity by modulating neuronal excitability of pre- and postsynaptic neuron populations, which has been shown to improve depression symptoms and cognition. We investigated the effects of a single session of 20 min of 2 mA left-prefrontal anodal versus sham stimulation on auditory event-related potentials (ERPs) in 11 male and 5 female healthy subjects (mean age of 28.6 [SD 6.2] years) by employing a randomized single-blind crossover design. Stimulation effects on cortical glutamate (Glu) and glutamine (Glx) levels were subsequently measured in 12 of the 16 healthy subjects in a 3 T proton magnetic resonance spectroscopy scan. tDCS was associated with a significant increase of N1 amplitudes while smaller P3b amplitudes correlated with higher cortical Glu and Glx levels in the stimulated brain area when performing an auditory go/no-go discrimination task. tDCS did not change mismatch negativity, nor task performance or cortical Glu/Glx levels which, together with N1 amplitudes, depended on stimulation order (“sham” versus “active”). Increased N1 amplitudes are consistent with higher levels of cortical excitability following prefrontal anodal tDCS. The failure to replicate Glu/Glx changes with tDCS may have been masked by between-session carry-over effects while ceiling effects may have masked tDCS effects on task performance.     

False recognition in a verbal memory task: an event-related potential study

Brain potentials were recorded from 15 healthy young subjects during the performance of a word recognition task. During the study phase, subjects had to intentionally memorise a series of words. These words were presented again together with the same number of new words in a following test phase where the instruction was to discriminate between repeated words and new words. We compared event-related potentials (ERPs) evoked by correctly identified repeated words (hits) and ERPs evoked by incorrectly classified new words (false alarms). Although both types of words were thought to be repeated the ERPs indicated differences between these two conditions starting at about 450 ms after the stimulus onset. These differences were mostly pronounced over frontal scalp locations but occurred also over parietal scalp locations (false alarms produced significantly more negative going ERPs than hits). We interpret that frontal and parietal brain areas show greater activation during false recognition because of a more intensive search for item representations.     

The P300 component decreases in a bimodal oddball task in individuals with depression: An event-related potentials study

Objective

In this study, we investigated auditory-visual stimulation-induced P300 and examined whether P300 was differentially modulated between individuals with clinical depression and healthy controls. We hypothesized that the P300 component would significantly differ between individuals with depression and healthy individuals Specifically, we predicted that the P300 component induced by the bimodal oddball task would be significantly different from that induced by the unimodal task.

The effects of repetitive transcranial magnetic stimulation on depressive symptoms and the P300 event-related potential

Changes in the Hamilton Depression Rating Scale and the P₃₀₀ auditory event-related potential were assessed in 10 patients with depression before and after a treatment course of five daily sessions of 10?Hz repetitive transcranial magnetic stimulation (rTMS) over the left prefrontal cortex. The patients were initially randomly allocated either to an active or a placebo rTMS treatment. All patients received both types of treatment separated by an interval of 4?weeks. The median Hamilton score decreased by 7 points following active rTMS and by 1?point after sham (p=0.075). Active rTMS was associated with a significant increase in the P₃₀₀ amplitude compared with sham (p=0.02). There was no correlation between changes in P₃₀₀ measurements and the Hamilton scores after active treatment. We conclude that five daily sessions of left prefrontal rTMS treatment is not of sufficient duration to make a significant improvement in depressive symptoms.     

An event-related brain potential study of auditory attention in cochlear implant users

ObjectiveCochlear implants (CIs) provide access to the auditory world for deaf individuals. We investigated whether CIs enforce attentional alterations of auditory cortical processing in post-lingually deafened CI users compared to normal-hearing (NH) controls.MethodsEvent-related potentials (ERPs) were recorded in 40 post-lingually deafened CI users and in a group of 40 NH controls using an auditory three-stimulus oddball task, which included frequent standard tones (Standards) and infrequent deviant tones (Targets), as well as infrequently occurring unique sounds (Novels). Participants were exposed twice to the three-stimulus oddball task, once under the instruction to ignore the stimuli (ignore condition), and once under the instruction to respond to infrequently occurring deviant tones (attend condition).ResultsThe allocation of attention to auditory oddball stimuli exerted stronger effects on N1 amplitudes at posterior electrodes in response to Standards and to Targets in CI users than in NH controls. Other ERP amplitudes showed similar attentional modulations in both groups (P2 in response to Standards, N2 in response to Targets and Novels, P3 in response to Targets). We also observed a statistical trend for an attenuated attentional modulation of Novelty P3 amplitudes in CI users compared to NH controls.ConclusionsERP correlates of enhanced CI-mediated auditory attention are confined to the latency range of the auditory N1, suggesting that enhanced attentional modulation during auditory stimulus discrimination occurs primarily in associative auditory cortices of CI users.SignificanceThe present ERP data support the hypothesis of attentional alterations of auditory cortical processing in CI users. These findings may be of clinical relevance for the CI rehabilitation.     

精神分裂症患者事件相关电位相关性研究

目的：探讨精神分裂症患者事件相关电位P300的特点及事件相关电位与阴性、阳性症状的相关性。方法：对28例精神分裂症患者及21名健康志愿者进行事件相关电位P300的检测。结果：两组靶刺激时P300的N2、P3潜伏期和P2、P3波幅有显著差异。结论：提示事件相关电位P300在协助精神分裂症的诊断、分型及推测预后方面有一定意义。     

Cognitive resource model for the information-processing of task-irrelevant visual stimuli

In order to elucidate possible factors that effect P3s to task-irrelevant visual stimuli (non-target P3s), we made a normative visual event-related potential study with button-press tasks in four different conditions in which two factors (the number of colors of non-target stimuli, and the shape of the stimuli) were manipulated without any change in task nor target/non-target ratio. The peak distributions of non-target P3s (centrally peaking) were significantly different from those of task-relevant P3s (parietally peaking) in all conditions. The amplitude of non-target P3 decreased as the variety of colors of the non-target stimuli increased. The amplitude of non-target P3 to colored solid circles was larger than that of non-target P3 to colored Stroop stimuli. Between each condition, task- relevant P3 and reaction time showed no significant difference. Both the variety of non-target stimuli and the shape of the stimuli were shown to have effects on the amplitudes of non-target P3s without any alteration in task-relevant P3s. It is suggested that the amplitude behaviors of non-target P3s partly reflect the amount of cognitive resource allocated for each different kind of task-irrelevant visual stimuli.     

Effect of vagal nerve stimulation on auditory and visual event-related potentials

Chronic unilateral vagal nerve stimulation (VNS) has been recently introduced into the therapy for intractable epileptic seizures. Its effect on cognitive functions in VNS-treated patients remains controversial. The aim of the present study was to evaluate the possible impact of therapeutic VNS on cognitive functions by means of event-related potentials analysis. Ten patients with medically intractable epilepsy, who had been implanted with VNS devices, participated in the study. Auditory and visual event-related potentials (ERPs) were repeatedly recorded, first just before the implantation of VNS devices, and then again 3-6 months after the device activation. The effect of lower intensity stimulation on the P3 component of ERPs was assessed. No significant differences were found in auditory ERPs; the latencies of P3 as well as N2/P3 peak-to-peak amplitudes were virtually identical. The same was true for mean P3 latencies of visual ERPs. However, higher visual N2/P3 peak-to-peak amplitudes were observed in the responses to targets that followed VNS, with a significant finding at the electrodes investigated. When comparing the effect of VNS on visual N2/P3 amplitude in each electrode separately, the most expressive differences were found in the frontal region. This observation supports the theory of a possible positive effect of low-intensity VNS on the cognitive functions.     

老年期抑郁症患者事件相关电位P300特征

目的：探讨有无自杀行为的老年期抑郁症患者认知功能的事件相关电位P300特征。方法：对60例老年期抑郁症患者（有自杀行为者20例,无自杀行为者40例）及60例性别、年龄匹配的正常老年人为对照,进行听觉诱发的事件相关电位P300检测。同时应用汉密尔顿抑郁量表（HAND）及老年认知功能量表（SECF）分别评价抑郁症组抑郁情绪及认知功能。结果：抑郁症组与对照组相比,P2、N2、P3潜伏期明显延长,P2、P3波幅明显降低;有自杀行为组N2、P3波幅比无自杀行为组明显降低。抑郁症组HAMD总分与P300各指标无相关,SECF总分与N2、P2、P3潜伏期显著负相关。结论：P300对老年期抑郁症患者早期认知功能损害评定具有一定价值,有、无自杀行为的老年期抑郁症患者认知功能损害不同。     

Dipolar source modeling of the P300 event-related potential after somatosensory stimulation.

The cerebral generators of the P300 potential evoked by somatosensory stimuli were investigated. Event-related potentials elicited by an oddball paradigm were recorded in 15 healthy subjects by 19 scalp electrodes. Nontarget and target electric stimuli were delivered on the anterior surface of the left elbow and of the wrist, respectively. Target traces showed an N140 potential followed by a widely distributed P300 response. Dipolar source modeling of target traces resulted in a six-dipole model. In the earlier latency range (up to 200 ms), one dipole in the contralateral perirolandic region and two dipoles in the parasylvian cortex of both hemispheres were activated. Two dipolar sources located bilaterally in the medial temporal region (MTR) showed their maximal activity at the P300 latency. Finally, a dipole in the contralateral frontal lobe was activated both at the latency of the N140 response and after 200 ms. It was found that two symmetrical MTR sources and a frontal dipole contributed to P300 generation.     

Event related potentials (ERP) and behavioral measurements to verbal stimulation of visual fields

Event related potentials (ERP) to visually presented linguistic stimuli were examined using a lexical-decision task and an oddball paradigm. Stimuli were presented to the central, right or left visual fields (CVF, RVF and LVF) and generated ERP with very clear N100-P300 components. The question addressed was whether there is ERP evidence for left hemisphere (LH) superiority in linguistic discrimination as reported behaviorally. Nineteen young, right-handed male subjects participated. The main factor influencing the latency and amplitude of N100 was that of contralateral versus ipsilateral stimulation. Shorter N100 latency and larger amplitude were recorded over the hemisphere contralateral to the visual field stimulated. In contrast, the factors influencing the P300 parameters were the visual field stimulated and the hemisphere over which the ERP was recorded. P300 amplitude was significantly larger and P300 latency significantly shorter over the LH than over the RH. Significantly shorter P300 latency and larger peak amplitude were found for RVF than for LVF stimulation.     

酒依赖的事件相关电位P300实验研究

目的　事件相关电位P30 0是一种特殊的脑诱发电位。本研究探讨酒依赖患者事件相关电位P30 0的基本特征。方法　使用丹麦丹迪SEEG 16道技术系统 ,以及听觉靶—非靶刺激序列为诱发事件 ,检测 2 6例男性酒依赖患者 ,并与 31例正常男性进行比较。结果　与正常男性相比 ,酒依赖患者ERP/P30 0波形有变异 ,稳定性差。酒依赖患者P30 0靶和非靶主成分潜伏期延迟 ,波幅下降 (P <0 0 5或P <0 0 1)。结论　提示长期大量饮酒对脑功能有损害。P30 0若干指标或许可以作为酒依赖的检测手段。     

Cognition in relapsing-remitting multiple sclerosis: a multichannel event-related potential (P300) study

Auditory event-related potentials (AERP) were elicited in 47 patients with relapsing-remitting (RR) multiple sclerosis (MS) and 24 age-matched controls. MS patients had significantly prolonged N2 and P3 latencies as well as low P3 amplitude compared with controls. Seven of them exceeded 3 standard deviations from the control mean values. The observed N2 and P3 alterations are associated with the patients' disability status as it is defined by the Kurtzke expanded disability status scale (EDSS), but are not related to the duration of the disease. A possible cognitive decline as reflected in the observed AERP components alterations in MS patients is subsequently discussed.     

An event-related potential study of contextual modifications in a face recognition task

Event-related potentials (ERP) were recorded during a task involving the short-term recognition of unfamiliar faces. The purpose was to study the effects of changing the intrinsic context (facial expression) and/or the extrinsic context (background) between the encoding and recognition of a face. The new face caused an increase in the parietal N170 amplitude, but this component was not affected by contextual modifications. In contrast, the frontal N200 was very sensitive to context changes. There was also a well-defined, late parietal component modulated by the processing of information relevant to the face recognition decision. This late positive component reached its amplitude peak when the decision criterion was the strictest. The results obtain showed that ERP can be modulated by these context variations even though they are irrelevant to the task at hand.     

Cognitive reserve modulates attention processes in healthy elderly and amnestic mild cognitive impairment: An event-related potential study

Objectives

The study aimed to investigate and compare the effect of cognitive reserve (CR) on brain activation in healthy controls (HC) and amnestic mild cognitive impairment (aMCI) patients during 0-back and 1-back tasks measured by event-related potential (ERP).

Intelligence and information processing during a visual search task in children: an event-related potential study

To investigate the differences in event-related potential parameters related to children's intelligence, we selected 15 individuals from an experimental class of intellectually gifted children and 13 intellectually average children as control to finish three types of visual search tasks (Chinese words, English letters and Arabic numbers). We recorded the electroencephalogram and calculated the peak latencies and amplitudes. Our results suggest comparatively increased P3 amplitudes and shorter P3 latencies in brighter individuals than in less intelligent individuals, but this expected neural efficiency effect interacted with task content. The differences were explained by a more spatially and temporally coordinated neural network for more intelligent children.     

Task reconfiguration and carryover in task switching: an event-related potential study

This study investigated the electrophysiological correlates of the processes involved in task switching. A pair-wise task-switching paradigm was used where each trial comprised two tasks that were either the same (task repeat) or different (task switch). In the paradigm, task-switch and repeat trials are compared in conditions of foreknowledge and non-foreknowledge of the forthcoming task type and during different response-stimulus intervals (RSIs). The results of this study show that, before the second task began in a task-pair trial, i.e., during the RSI, there was a CNV-like negativity for all trials. This indicates a general anticipatory effect. In foreknowledge conditions, there is an additional switch-specific reconfiguration process followed by a task-specific (including both switch- and repeat-related) preparatory process. During the post-task 2 stage, P3b was found to be smaller in switch trials than in repeat trials. Such differential P3b between switch and repeat trials appeared earlier and larger in foreknowledge than in non-foreknowledge conditions. The results of this study support the existence of advance preparation and uphold the role of carryover effects in task switching.     

汉、维吾尔族神经症患者视觉事件相关电位P300对比研究

目的：探讨汉族与维吾尔族神经症患者视觉事件相关电位P300的异同。方法：选97例神经症患者作为神经症组（汉族48例,维族49例）,99例健康者作为对照组（汉族45例,维族47例）,对所有入组者均进行视觉事件相关电位P300检测并比较。结果：两组中汉族和维吾尔族神经症患者的靶N2潜伏期、靶P3潜伏期及波幅、非靶P2波幅差异均无统计学意义（P均〉0.05）;与正常对照组比较,汉族与维吾尔族神经症患者的靶N2潜伏期均延长（P均〈0.05）,靶P3潜伏期均延长且波幅降低（P均〈0.05）,非靶P2波幅均降低（P〈0.05）。结论：汉族与维吾尔族神经症患者的视觉事件相关电位P300差异无统计学意义;神经症患者的视觉事件相关电位P300有多项指标变化。     

An event-related brain potential study of receptive speech comprehension using a modified Token Test

There is a long and distinguished history of evaluating sensory functions with evoked potentials (EPs). However, the clinical utility of event-related brain potentials (ERPs) in the assessment of cognitive functions remains to be established. We present evidence for the efficacy of ERPs in the assessment of speech comprehension. In this normative study, a version of the Token Test (Boller and Vignolo, 1966, Brain, 89, 815–831; De Renzi and Vignolo, 1962, Brain, 85, 665–678) was modified for computer presentation with simultaneous ERP recordings and then administered to a group of healthy individuals (n=27). A differential neural response pattern to incorrect and correct test items was obtained for the group and, more importantly, this result was also observed reliably at the individual subject level. This research complements on-going efforts in our laboratory to develop innovative measures for patients that are difficult or impossible to assess due to motoric and/or communicative limitations.