Low-resolution Brain Electromagnetic Tomography Analysis Research Articles

Modification of cortical electrical activity in stroke survivors with abnormal subjective visual vertical: An eLORETA study

ObjectivesBalance impairment is among the main complications of stroke. The gravity-based subjective vertical (SV) is considered an important reference for upright posture and navigation affected by stroke. The correlation between injury location and pathological perception of verticality remains controversial. This study aimed to evaluate the cortico-cortical network of vertical perception among patients with the right hemisphere stroke and abnormal visual-vertical perception compared with healthy individuals. Materials and methodsThis observational cross-sectional study included 40 patients with the right hemisphere stroke and 35 healthy participants. All patients had abnormal visual-vertical perception. The EEG connectivity analysis was conducted through the exact low-resolution brain electromagnetic tomography analysis (eLORETA). ResultsStroke survivors manifested a power spectral density that reduced within the beta-2 frequency band in the left hemisphere and increased within the beta-3 frequency band in the right hemisphere compared with controls (p < 0.01). The lagged-phase synchronization was increased within alpha-1, beta-2, and beta-3 bands and decreased in stroke survivors compared with controls in the vestibular network involved in visual-vertical perception (p < 0.01). ConclusionThe results of this study demonstrated variations in the function and functional connectivity of cortical areas involved in the visual-vertical perception that are mainly located in the vestibular cortex.

The Electropsychology of Mind, a Newfangled Route in Psychology by Utilizing Electrophysiological Means to Detect Mental Health Problems

Purpose: Modern electroencephalography or E.E.G analysis methods like quantitative-electroencephalography or Q.E.E.G entail capturing computerized E.E.G data and thereafter processing, transforming, and analyzing those outputs employing sophisticated computational methods. Q.E.E.G has introduced unique methods for extracting E.E.G signal features; including interconnection, circuit, as well as regularity range evaluation, and also signal intricacy assessment. Numerous therapeutic conditions, such as neuropsychological diseases, seizures, ischemia, Alzheimer, brain trauma, psychological issues, as well as more are treated with Q-E.E.G. In this paper, will be going over the available data on the real-world uses of this therapeutic technique in psychopathological cases. Objective: The primary objective of this article is to describe electrophysiological alterations in numerous well-known and widespread mental disorders. Another goal of this research is to spot electrophysiological alterations in attention disorder, a prevalent and nowadays more prevalent social disorder. In this instance, it will be examined using both electrophysiological research and low-resolution brain electromagnetic tomography analysis. The use of Q-EEG over conventional EEG is growing in popularity right now, and that trend will continue in the future. In this regard, another goal of this paper is to provide some insight into some of the areas of research or application where Q-E.E.G. can be used to its fullest potential. Design/Methodology/Approach: Scientific secondary clinical data from a variety of reputable and credible sources and publications, including Google Scholar, Academia, Researchgate, etc., were used to construct this research. A thorough, methodical, and scientific analysis has been performed to obtain the substance of all the scientific journal research results in order to make this article more accurate, dependable, and scientific. To make this article more engaging and trustworthy, opinions from a range of experienced specialists were gathered. In order to cover nearly all of the common and specific areas of knowledge regarding this issue, more than a hundred journal papers and conference proceedings have been methodically studied. Finding/Results: There is no one framework or integrated technique that can handle the tremendous amount of data that the E.E.G. capture generates. Comparing laboratory data is challenging because each investigator employs their own analytical frameworks. Similar to Q-E.E.G, this massive disparity prevents the creation of a novel, cohesive and replaceable information database. Understanding all the graphs and figures generated by the newest devices may be difficult for experts other than neurophysiologists. In conclusion, determining a clinical diagnosis of intellectual disability is a challenging process that depends on a variety of data. Given this, software-assisted assessment using Q-E.E.G. offers helpful assistance for identifying, evaluating, monitoring and determining responsiveness to intervention. It is accurate, reasonably priced, as well as manageable to use. Originality and Value: A novel effort has been made to depart some information regarding electrophysiological changes in various mental disorders. In order to make the paper clear and vivid, images of different EEG reports have been attached. The paper was built in such a way that the readers could understand this clinical topic regardless of their academic qualifications. A novel terminology, "Electropsychology,” has been used to refer to the electrophysiological alterations of mental disorders on an EEG paper, which is exclusively intended to rule out the mental disorder. Paper Type: Clinical analysis paper

Intertemporal preference reversals are associated with early activation of insula and sustained preferential processing of immediate rewards in visual cortex

Decision makers tend to give magnified significance to immediately available rewards which leads to intertemporal preference reversals, which is a form of self-control failure. The objective of the present study was to understand the cognitive and neural underpinnings of this phenomenon using event-related potentials (ERP) and their source localization using standardized low-resolution brain electromagnetic tomography analysis (sLORETA). Twenty-four participants performed a money choice task, where they made choices between a smaller-sooner and a larger-later reward, which included trials with and without an immediately available option, while their electroencephalography (EEG) activity was recorded. Trials with and without immediacy were identical except that the latter involved a front-end delay added to both the rewards. Results showed that presence of immediacy made the choices significantly more impulsive. Presence of immediate reward elicited larger visual P2 and late positive potential (LPP), indicating enhanced capture of automatic and sustained attention respectively, and smaller N2, indicative of diminished engagement of cognitive control processes. Source localization revealed increased activity in the visual cortex in the presence of immediacy, signifying higher valuation. Higher activation of areas of insula during P2—suggesting increased awareness of visceral signals—predicted larger impulsive preference reversals. The results suggest that presence of immediate reward biases the choice very early during the decision making process by precipitating visceral states that triggers approach behaviour, and highlight the need to adopt strategies like precommitment to counter the effect.

Spectrum-specific encephalography standardized low-resolution brain electromagnetic tomography network and gray matter correlations in vascular dementia patients

Vascular dementia, secondary to Alzheimer’s dementia, ranks as one of the most frequent dementia types. The process of vascular dementia is divergent with other neurodegenerative dementias and thus reversible at the early cognitive disorder or mild dementia stages. The encephalography and neuroimaging data mining at different stages would bring neuromodulation strategies in practice; 15 mild cognitive impairment patients and 16 mild vascular dementia patients as well as 17 cognitive healthy controls were screened in this study. Cognitive tests such as Mini-Mental State Examination, Montreal cognitive assessment, voxel-based morphometry, electroencephalography, and standardized low-resolution brain electromagnetic tomography connectivity network were conducted. Compared with healthy group, voxel-based morphometry analysis showed a decrease in gray/cerebrospinal fluid ratio ( p &lt; .05) in mild dementia group; the energy power of gamma band decreased ( p &lt; .05) in mild dementia group; and electroencephalography standardized low-resolution brain electromagnetic tomography analysis showed wider frontal and temporal lobe involvement in mild dementia patients ( p &lt; .05). Network topological analysis screened top 10 key Brodmann areas (44R, 7R, 8L, 22L, 47L, 27L, 1L, 1R, 7R, 43L), which could be underlying neuromodulators for dementia patients. Electroencephalography as well as structural magnetic resonance imaging could be used for the evaluation of cognitive disorder patients. The spectrum-specific standardized low-resolution brain electromagnetic tomography analysis and connectivity network analysis could shed light on the neuromodulator targets in the early phase of dementia.

P1‐227: DEFICITS IN EXECUTIVE FUNCTION IN AMNESTIC MILD COGNITIVE IMPAIRMENT: EVENT‐RELATED POTENTIALS STUDY DURING STROOP COLOR‐WORD TASK

Previous investigations showed that Alzheimer's disease (AD)-related executive function deficits start near the beginning of mild cognitive impairment (MCI) phase of itself. The study aimed to explore deficits in executive function in amnestic MCI (aMCI) with Event-Related Potentials (ERPs) study. The ERP data were measured and analyzed in 30 aMCI and 38 healthy elderly controls (HEC) during Stroop Color-Word Task (SCWT). The study indicated that aMCI patients showed decreased accuracy (ACC) and delayed reaction time (RT) in incongruent condition, compared to HEC (all p < 0.05). Additionally, aMCI patients showed greater N450 amplitudes of a difference wave between ERPs elicited by incongruent and congruent stimuli at Fz electrode, compared to HEC (all p < 0.05). Moreover, standardized low-resolution brain electromagnetic tomography analysis (sLORETA) study showed a hyperactivation in the left inferior parietal lobule (IPL) in the contrast for the incongruent condition relative to the congruent condition, compared to HEC during N450 time range (p < 0.05). The study showed deficits in conflict processing in aMCI with an ERP study. And the deficits might derive from the left IPL. Hence, the study demonstrated that ERP with SCWT was a sensitive biomarker for recognizing aMCI patients from HEC.

Deficits of visuospatial working memory and executive function in single- versus multiple-domain amnestic mild cognitive impairment: A combined ERP and sLORETA study

ObjectiveAccording to recent criteria of classification, amnestic mild cognitive impairment (aMCI) could be divided into two categories: single-domain aMCI (sd-aMCI) and multiple-domain aMCI (md-aMCI). The difference between sd-aMCI and md-aMCI needs further exploration. The present study aimed to compare deficits in visuospatial working memory (VSWM) and executive function between sd-aMCI versus md-aMCI patients by use of event-related potentials (ERP) and standardized low-resolution brain electromagnetic tomography analysis (sLORETA). MethodsThe ERP data were measured and analyzed in 26 sd-aMCI, 13 md-aMCI patients and 46 healthy elderly controls (HEC) during VSWM and Go/Nogo processes. ResultsDuring VSWM task, md-aMCI patients showed decreased P300 amplitude compared to HEC and sd-aMCI patients (All p < 0.05). As compared to sd-aMCI, md-aMCI showed a hypoactivation in the right middle frontal gyrus in 1-back task during the P300 time range. During the Go/Nogo task, sd-aMCI and md-aMCI patients showed reduced N200 amplitude, compared to HEC (All p < 0.05). However, md-aMCI patients had decreased N200 amplitude, with respect to sd-aMCI patients. Further, as compared to sd-aMCI patients, md-aMCI patients showed a hypoactivation in the right superior frontal gyrus during the N200 time range. ConclusionsThese findings with a combined ERP and sLORETA study showed more severe deficits in updating operations of WM, detections of the target stimulus and conflict processes in md-aMCI, compared to sd-aMCI patients. SignificanceThe present study showed that a combined ERP and sLORETA study during the VSWM and Go/Nogo tasks could distinguish md-aMCI from sd-aMCI.

GLOBAL SYNCHRONIZATION INDEX AS A NEW INDICATOR FOR TRACKING COGNITIVE FUNCTION CHANGES BY TRANSCRANIAL DIRECT CURRENT STIMULATION IN A TRAUMATIC BRAIN INJURED PATIENT: A CASE REPORT

Traumatic brain injury (TBI) is a leading cause of long-term neurological disability such as cognitive impairments and executive dysfunction. Noninvasive transcranial direct current stimulation (tDCS), which can change brain excitability, was introduced and has been applied for therapeutic purposes regarding cognitive dysfunction after TBI. We investigated the effect of tDCS on the cognitive function and cortical power distribution by dual analysis of resting state Electroencephalography (EEG) with Global Synchronization Index (GSI) and Low-Resolution Brain Electromagnetic Tomography Analysis (LORETA) in a TBI patient. A 77-year-old male, who went through a traumatic brain injury showed severe impairment of cognitive function. We performed 20 sessions of 2mA tDCS over the left dorsolateral prefrontal cortex (DLPFC) and measured Korean version of the Mini-Mental Status Examination (K-MMSE) and Rancho Los Amigos (RLA) level at baseline, 10 days and 20 days each after tDCS. EEG was also performed on same days with K-MMSE and RLA tests. After tDCS, the cognitive function measured by K-MMSE and RLA level were improved. GSI showed decrease in the low frequency band (theta wave) and increase in high frequency bands (alpha and beta wave) (Table 1). LORETA analysis showed incresed cortical activation components in high frequency bands at 20 days after tDCS (Figure 1). Graphical representation of the LORETA results comparing the EEG between baseline and tDCS 10 (a) and between baseline and tDCS 20 (b). Blue-light blue colors indicate increased component and yellow-red colors indicate decreased component of each EEG bands. We suggest that tDCS might be effective in TBI patients, and the alterations of cognitive networks could be effectively studied using GSI analysis together with LORETA.

The Effect of Apolipoprotein E ε4 (APOE ε4) on Visuospatial Working Memory in Healthy Elderly and Amnestic Mild Cognitive Impairment Patients: An Event-Related Potentials Study.

Background: Apolipoprotein E (APOE) ε4 is the only established risk gene for late-onset, sporadic Alzheimer’s disease (AD). Previous studies have provided inconsistent evidence for the effect of APOE ε4 status on the visuospatial working memory (VSWM).Objective: The aim was to investigate the effect of APOE ε4 on VSWM with an event-related potential (ERP) study in healthy controls (HC) and amnestic mild cognitive impairment (aMCI) patients.Methods: The study recorded 39 aMCI patients (27 APOE ε4 non-carriers and 12 APOE ε4 carriers) and their 43 matched controls (25 APOE ε4 non-carriers and 18 APOE ε4 carriers) with an 64-channel electroencephalogram. Participants performed an N-back task, a VSWM paradigm that manipulated the number of items to be stored in memory.Results: The present study detected reduced accuracy and delayed mean correct response time (RT) in aMCI patients compared to HC. P300, a positive component that peaks between 300 and 500 ms, was elicited by the VSWM task. In addition, aMCI patients showed decreased P300 amplitude at the central–parietal (CP1, CPz, and CP2) and parietal (P1, Pz, and P2) electrodes in 0- and 1-back task compared to HC. In both HC and aMCI patients, APOE ε4 carriers showed reduced P300 amplitude with respect to non-carriers, whereas no significant differences in accuracy or RT were detected between APOE ε4 carriers and non-carriers. Additionally, standardized low-resolution brain electromagnetic tomography analysis (s-LORETA) showed enhanced brain activation in the right parahippocampal gyrus (PHG) during P300 time range in APOE ε4 carriers with respect to non-carriers in aMCI patients.Conclusion: It demonstrated that P300 amplitude could predict VSWM deficits in aMCI patients and contribute to early detection of VSWM deficits in APOE ε4 carriers.

The effect of apolipoprotein E ɛ4 (APOE E4) on visuospatial working memory in healthy elders and amnestic mild cognitive impairment patients: An event-related potentials study

IntroductionPrevious studies provided inconsistent evidences for the effect of apolipoprotein E ɛ4 (APOE ɛ4) status on the visuospatial working memory (VSWM). Our study was the first investigation with event-related potential (ERP) to explore the effect of APOE ɛ4 on VSWM in healthy elders and aMCI patients.ObjectiveThe aim was to investigate the effect of APOE ɛ4 on VSWM with event-related potential (ERP) study in healthy elders and aMCI patients.MethodsThirty-nine aMCI patients (27 APOE ɛ4 non-carriers and 12 APOE ɛ4 carriers) and 43 their matched control (25 APOE ɛ4 non-carriers and 18 APOE ɛ4 carriers) performed an N-back task, a VSWM paradigm that manipulated the number of items to be stored in memory.ResultsOur study detected reduced accuracy and delayed mean correct response time in aMCI patients than healthy elders. P300 was elicited by VSWM and its amplitude was lower in aMCI patients at the central-parietal and parietal electrodes than healthy controls. In healthy elders, P300 amplitude declined prior to task performance change in APOE ɛ4 carriers than non-carriers. Regarding aMCI patients, P300 amplitude result revealed exacerbated VSWM deficits in APOE ɛ4 carriers than APOE ɛ4 non-carriers. Additionally, standardized low-resolution brain electromagnetic tomography analysis (s-LORETA) result showed enhanced brain activation in right parahippocampal gyrus during P300 time range in APOE ɛ4 carriers than non-carriers in aMCI patients (Fig. 1, Tables 1 and 2).ConclusionsIt demonstrated that P300 amplitude might serve as a biomarker for recognizing aMCI patients and contribute to early detection of worse VSWM in APOE ɛ4 carriers than non-carriers.Disclosure of interestThe author has not supplied his/her declaration of competing interest.

Towards a method to differentiate chronic disorder of consciousness patients' awareness: The Low-Resolution Brain Electromagnetic Tomography Analysis

Assessing residual signs of awareness in patients suffering from chronic disorders of consciousness (DOC) is a challenging issue. DOC patient behavioral assessment is often doubtful since some individuals may retain covert traces of awareness; thus, some Unresponsive Wakefulness Syndrome (UWS) patients may be misdiagnosed. The aim of our study was to explore possible differences between the source powers within poly-modal cortices to differentiate Minimally Conscious State (MCS) from UWS. To this end, we recorded an electroencephalogram (EEG) during awake resting state and performed a Low-Resolution Brain Electromagnetic Tomography (LORETA), which is a 3D source localization method allowing the visualization of the most probable neuroanatomical generators of EEG differences. MCS and UWS patients showed significant variations concerning the frontal source power of delta-band, frontal and parietal of theta, parietal and occipital of alpha, central of beta, and parietal of gamma, in correlation with the Coma Recovery Scale-Revised (CRS-R) score. The alpha-band was the most significant LORETA data correlating with the consciousness level. In addition, we observed a significant correlation between central beta-peaks and the motor abilities and a dissociation between theta and gamma bands within parietal regions. Our findings suggest that LORETA analysis may be useful in DOC differential diagnosis since distinct neurophysiological correlates in some UWS patients could be used to assess deeper the residual cerebral activity of brain areas responsible for covert awareness.

Prediction of Treatment Outcome in Patients with Obsessive-Compulsive Disorder with Low-Resolution Brain Electromagnetic Tomography: A Prospective EEG Study.

The issue of predicting treatment response and identifying, in advance, which patient will profit from treating obsessive-compulsive disorder (OCD) seems to be an elusive goal. This prospective study investigated brain electric activity [using Low-Resolution Brain Electromagnetic Tomography (LORETA)] for the purpose of predicting response to treatment. Forty-one unmedicated patients with a DSM-IV diagnosis of OCD were included. A resting 32-channel EEG was obtained from each participant before and after 10 weeks of standardized treatment with sertraline and behavioral therapy. LORETA was used to localize the sources of brain electrical activity. At week 10, patients were divided into responders and non-responders (according to a reduction of symptom severity >50% on the Y-BOCS). LORETA analysis revealed that at baseline responders showed compared to non-responders a significantly lower brain electric activity within the beta 1 (t = 2.86, p < 0.05), 2 (t = 2.81, p < 0.05), and 3 (t = 2.76, p < 0.05) frequency bands and ROI analysis confirmed a reduced activity in alpha 2 (t = 2.06, p < 0.05) in the anterior cingulate cortex (ACC). When baseline LORETA data were compared to follow-up data, the analysis showed in the responder group a significantly lower brain electrical resting activity in the beta 1 (t = 3.17. p < 0.05) and beta 3 (t = 3.11. p < 0.05) frequency bands and equally for the ROI analysis of the orbitofrontal cortex (OFC) in the alpha 2 (t = 2.15. p < 0.05) frequency band. In the group of non-responders the opposite results were found. In addition, a positive correlation between frequency alpha 2 (rho = 0.40, p = 0.010), beta 3 (rho = 0.42, p = 0.006), delta (rho = 0.33, p = 0.038), theta (rho = 0.34, p = 0.031), alpha 1 (rho = 0.38, p = 0.015), and beta1 (rho = 0.34, p = 0.028) of the OFC and the bands delta (rho = 0.33, p = 0.035), alpha 1 (rho = 0.36, p = 0.019), alpha 2 (rho = 0.34, p = 0.031), and beta 3 (rho = 0.38, p = 0.015) of the ACC with a reduction of the Y-BOCS scores was identified. Our results suggest that measuring brain activity with LORETA could be an efficient and applicable technique to prospectively identify treatment responders in OCD.

Activation of the serotonergic system by pedaling exercise changes anterior cingulate cortex activity and improves negative emotion

Pedaling exercise (PE) of moderate intensity has been shown to ease anxiety and discomfort; however, little is known of the changes that occur in brain activities and in the serotonergic (5-HT) system after PE. Therefore, this study was conducted for the following reasons: (1) to localize the changes in the brain activities induced by PE using a distributed source localization algorithm, (2) to examine the changes in frontal asymmetry, as used in the Davidson model, with electroencephalography (EEG) activity, and (3) to examine the effect of PE on the 5-HT system. A 32-channel EEG was used to record before and after PE. Profile of Mood States tests indicated that there was a significant decrease in tension-anxiety and a significant increase in vigor after PE. A standardized low-resolution brain electromagnetic tomography analysis showed a significant decrease in brain activities after PE in the alpha-2 band (10–12.5Hz) in the anterior cingulate cortex (ACC). Moreover, a significant increase in frontal EEG asymmetry was observed after PE in the alpha-1 band (7.5–10Hz). Urine 5-HT levels significantly increased after PE. Urine 5-HT levels positively correlated with the degree of frontal EEG asymmetry in the alpha-1 band and negatively correlated with brain activity in ACC. Our results suggested that PE activates the 5-HT system and consequently induces increases in frontal EEG asymmetry in the alpha-1 band and reductions of brain activity in the alpha-2 band in the ACC region.

Ictal EEG Source Imaging in Frontal Lobe Epilepsy Leads to Improved Lateralization Compared With Visual Analysis

To investigate the utility of EEG source imaging to lateralize ictal patterns in frontal lobe epilepsy, which were nonlateralized by standard EEG analysis. Prospective analysis of 17 seizures in 8 patients with unilateral frontal lobe epilepsy MRI lesions and nonlateralizing ictal scalp EEG. We applied four EEG source imaging techniques (phase maps, symmetric dipoles, low-resolution brain electromagnetic tomography analysis, and classical low-resolution brain electromagnetic tomography analysis recursively applied) to the averaged seizure pattern. We tested (1) the ability of these techniques to lateralize seizure patterns, (2) the agreement of the lateralization result with MRI lesion side and subdural EEG recordings, individually for each method and for concordance of all. We found lateralizing results in 5 of 17 seizures when analyzing phase maps, 8 of 17 when analyzing dipoles, and 5 of 17 in both classical low-resolution brain electromagnetic tomography analysis recursively applied and low-resolution brain electromagnetic tomography analysis. No discordance with the MRI lesion side was seen when analyzing phase maps, whereas dipole analysis was discordant to the MRI lesion in two seizures, classical low-resolution brain electromagnetic tomography analysis recursively applied in one, and low-resolution brain electromagnetic tomography analysis in two. Agreement between all imaging methods was found in three seizures (three patients), all in line with the side of the MRI lesion. Advanced EEG review methods and source localization provide useful lateralizing information in difficult frontal lobe epilepsy seizure patterns.

Electrical Source Imaging of Sleep Spindles

To identify and compare cortical source generators of slow and fast sleep spindles in healthy subjects, electroencephalographic (EEG) signals were obtained from 256 channels, and sources on neuroanatomical Montreal Neurological Institute (MNI) space estimated with low-resolution brain electromagnetic tomography analysis (LORETA). Spindle activity was recorded in 18 healthy volunteers during daytime napping. Because of lack of sleep or excessive artifacts, data from 13 subjects were analyzed off-line. Spindles were visually scored, marked, and bandpass filtered (slow 10-12 Hz or fast 12-14 Hz). EEG was segmented on the marker, and segments separately averaged. LORETA projected cortical sources on the MNI brain. Maximal intra- and inter-individual intensities were compared using the Wilcoxon test (P < .05) and cortical sources distribution compared using a chi2 test. Two to three slow spindles generators were consistently identified in frontal lobes, with additional sources in parietal and limbic lobes in half cases. Fast spindles had multiple temporo-parietal sources, with an inconstant frontal source. Inter-individual (P = 0.44), and intra-individual (P = 0.09 slow and P = 0.10 fast spindles) source intensities were comparable. Slow spindles sources were preferentially concentrated over frontal cortices in comparison with fast spindles (P = 0.0009). Our results demonstrate multiple, synchronous, and equipotent spindles cortical generators in healthy subjects, with more anterior generators for slow spindles.

&lt;b&gt;The process in the change of brain activity during habituation to the inner experience of pain &lt;/b&gt;&lt;b&gt;—a study using Electroencephalogram— &lt;/b&gt;

Habituation to pain has been addressed in many recent studies. It is clear that patients with chronic pain do not become habituated to the pain; however, little is known about habituation to the inner experience of pain. We investigated the brain mechanisms underlying habituation to the inner experience of pain by using event-related potentials (ERPs), which provide superior temporal resolution, and low-resolution brain electromagnetic tomography (LORETA), which enables identification of regions of nervous activity. Fifteen healthy subjects participated in this study. The subjects were shown 4 sets of photographic images, with each set shown 30 times. The images included 15 images of a hand subjected to pain (painful condition). The subjects were instructed to imagine themselves in that condition and to imagine the pain they may experience in such a situation (inner experience of pain). Electroencephalography was continuously performed via 128 scalp electrodes mounted on an electrode cap. ERPs were recorded during the inner experience of pain; we also recorded N110 responses for emotional components and P3 responses for cognitive evaluation. To investigate habituation to the inner experience of pain, the mean amplitudes of P3 and N110 recordings were calculated for the first 2 (early sets) and last 2 (late sets) sets of trials for each painful condition; next, early sets were compared with late sets. We also analyzed the change in nervous activity after habituation to the inner experience of pain by LORETA analysis. The amplitude of central P3 responses was significantly lower for the late image sets than the early image sets of the painful condition. However, the mean amplitude of N110 responses did not significantly change. LORETA analysis of P3 responses showed reduced activity in the left secondary somatosensory area and left posterior insular cortex, indicating that the sensory component of the inner experience of pain was lower in the late sets than in the early sets. During habituation to the inner experience of pain, the P3 response, which is related to cognitive evaluation of this experience, changed, and brain activity, which reveals the sensory component of the inner experience of pain, reduced. Our study suggests that habituation to the inner experience of pain occurs at the point of recognition of the sensory component of pain. We hypothesize that pain recognition necessary for habituation to the inner experience of pain.

LORETA analysis of three-dimensional distribution of delta band activity in schizophrenia: Relation to negative symptoms

We sought to determine if altered electroencephalography (EEG) activities, such as delta band activity, in specific brain regions are associated with psychotic symptoms. Data were obtained from 17 neuroleptic-naive patients with schizophrenia and age- and sex-matched 17 healthy control subjects. Low Resolution Brain Electromagnetic Tomography (LORETA) was used to generate current source density images of delta, theta, alpha, and beta activities. Localization of the difference in EEG activity between the two groups was assessed by voxel-by-voxel non-paired t-test of the LORETA images. Spearman's correlation coefficient was obtained to relate LORETA values of EEG current density in brain regions showing a significant between-group difference and psychopathology scores. Delta band activity, represented by LORETA current density, was greater for patients in the following areas; the left inferior temporal gyrus, right middle frontal gyrus, right superior frontal gyrus, right inferior frontal gyrus, and right parahippocampal gyrus. LORETA values for delta band activity in the above five brain regions were negatively correlated with negative, but not positive symptoms. The results of this study suggest the role for electrophysiological changes in some of the brain regions, e.g. prefrontal cortex, in the manifestation of negative symptoms.

Reduced Early Auditory Evoked Gamma-Band Response in Patients with Schizophrenia

There is growing evidence for abnormalities of certain gamma-aminobutyric acid (GABA)-ergic interneurons and their interaction with glutamatergic pyramidal cells in schizophrenia. These interneurons are critically involved in generating neural activity in the gamma-band (30-100 Hz) of the electroencephalogram. One example of such gamma oscillations is the early auditory evoked gamma-band response (GBR). Although auditory processing is obviously disturbed in schizophrenia, there is no direct evidence providing a reduced early auditory evoked GBR so far. We addressed two questions: 1) Is the early auditory evoked GBR decreased regarding power and phase-locking in schizophrenic patients?; and 2) Is this possible decrease a result of reduced activity in the auditory cortex and/or the anterior cingulate cortex (ACC), which were identified as sources of the GBR previously? We investigated the early auditory evoked GBR and its sources in the ACC and the auditory cortex in 90 medicated patients with schizophrenia and in age-, gender-, and education-matched healthy control subjects with an auditory reaction task. Patients with schizophrenia showed a significant reduction of power and phase-locking of the early auditory evoked GBR. This effect was due to a reduced activity in the auditory cortex and the ACC/medial frontal gyrus region (low-resolution brain electromagnetic tomography analysis). Generally, these findings are in line with earlier reports on the impaired ability of schizophrenic patients in generating gamma activity. In addition, this is the first study to demonstrate disturbance of gamma activity in auditory processing as assessed by the early auditory GBR power.

Effects of cortisol on the laterality of the neural correlates of episodic memory

Alterations in the laterality of cortical activity have been shown in depressive illnesses. One possible pathophysiological mechanism for this is an effect of corticosteroids. We have previously demonstrated that endogenous cortisol concentrations correlate with the asymmetry of cortical activity related to episodic memory in healthy subjects and depressed patients. To further-examine whether this is due to a causal effect of cortisol on the laterality of episodic memory, we studied the effect of exogenous administration of cortisol in healthy subjects. Twenty-three right-handed healthy male volunteers were tested in a double-blind cross-over study. Event-related potentials (ERPs) were recorded during an episodic memory task following a four-day course of 160 mg/day cortisol or placebo. Low-resolution brain electromagnetic tomography (LORETA) was used to identify brain regions involved in the neurocognitive task. Cortisol levels were measured in saliva samples. ERP and LORETA analysis following placebo demonstrated significant left parahippocampal activation associated with successful retrieval. Cortisol led to a decrease in the mean early frontal ERP voltage and an increase in the late right ERP voltage. LORETA suggested this to be due to a significant increased late activation of the right superior frontal gyrus. There was no significant effect of cortisol on episodic memory performance. This study suggests that exogenous cortisol leads to more positive-going waveforms over the right than the left hemisphere, possibly due to increased monitoring of the products of retrieval. The results support the hypothesis of causal effects of cortisol on the laterality of cortical activity occurring during an episodic memory task.

Abnormalities of the contingent negative variation in Huntington's disease: Correlations with clinical features

The contingent negative variation (CNV) is a neurophysiological pattern related to planning of external — paced, voluntary movements. The aim of the study, was to examine the CNV in a cohort of mild demented and non-medicated HD patients, evaluating the CNV amplitude modifications in the light of clinical features and performing Low Resolution Brain Electromagnetic Tomography (LORETA) analysis in order to show the CNV multiple generators. Fourteen HD patients and 25 sex and age-matched controls were studied. All subjects were evaluated by the motor section of UHDRS, MMSE and WAIS. The CNV was recorded by 19 scalp electrodes, with a red light flash as visual warning stimulus (S1), followed by a blue light flash (S2) after a fixed interval of 3 s. The amplitude of early CNV was significantly reduced in HD, compared to controls: the amplitude reduction was significantly correlated with the bradikinesia score. LORETA analysis of early CNV significantly discriminated patients from controls, for a prevalent activation of the posterior part of anterior cingulate cortex in HD. An abnormal activation of the associative cortex devoted to the processing of attention preceding voluntary movement may be supposed in HD, probably mediated by the altered basal ganglia modulation.

Focal Cortical Dysfunction and Blood???Brain Barrier Disruption in Patients With Postconcussion Syndrome

Postconcussion syndrome (PCS) refers to symptoms and signs commonly occurring after mild head injury. The pathogenesis of PCS is unknown. The authors quantitatively analyzed EEG recordings, localized brain sources for abnormal activity, and correlated it with imaging studies. Data from 17 patients with neurologic symptomatology consistent with ICD-10 criteria for PCS was analyzed. Normalized quantitative EEG (QEEG) revealed significantly higher power in the delta band and lower power in the alpha band compared with matched controls. The generators for the abnormal rhythms were focally localized in neocortical regions. Brain computerized tomography and/or MRI did not reveal focal abnormality at the time of diagnosis. Single photon emission computed tomography (SPECT) after 99mTc-ethylcysteinate dimer administration showed a focal reduction in perfusion in 85% (n = 11) of the patients, and abnormal blood-brain barrier (BBB) after 99mTc-diethylenetriaminepentaacetic acid administration in 73% (n = 8). In 75% of these patients, low-resolution brain electromagnetic tomography analysis showed that the generators for abnormal rhythms were closely related to the anatomic location of the BBB lesion. These data point to focal cortical dysfunction in conjunction with BBB disruption and hypoperfusion as a possible mechanism of pathogenesis in at least some PCS patients, and offer QEEG and SPECT as important tools in evaluating these patients.