Assessment of Classical and Non-Classical Quantitative Electroencephalographic Measures in Patients with Substance Use Disorders.

Background: People diagnosed with substance use disorders (SUDs) are at risk for impairment of brain function and structure. However, physicians still do not have any clinical biomarker of brain impairment that helps diagnose or treat these patients when needed. The most common method to study these patients is the classical electroencephalographic (EEG) analyses of absolute and relative powers, but this has limited individual clinical applicability. Other non-classical measures such as frequency band ratios and entropy show promise in these patients. Therefore, there is a need to expand the use of quantitative (q)EEG beyond classical measures in clinical populations. Our aim is to assess a group of classical and non-classical qEEG measures in a population with SUDs. Methods: We selected 56 non-medicated and drug-free adult patients (30 males) diagnosed with SUDs and admitted to Rehabilitation Clinics. According to qualitative EEG findings, patients were divided into four groups. We estimated the absolute and relative powers and calculated the entropy, and the alpha/(delta + theta) ratio. Results: Our findings showed a significant variability of absolute and relative powers among patients with SUDs. We also observed a decrease in the EEG-based entropy index and alpha/(theta + delta) ratio, mainly in posterior regions, in the patients with abnormal qualitative EEG. Conclusions: Our findings support the view that the power spectrum is not a reliable biomarker on an individual level. Thus, we suggest shifting the approach from the power spectrum toward other potential methods and designs that may offer greater clinical possibilities.

Acceptability by End-users of a Standardized Structured Format for Reporting EEG.

The report of the electroencephalogram (EEG) results has traditionally been made using free-text formats with a huge variation in descriptions due to several factors. Recently, the International Federation of Clinical Neurophysiology (IFCN) endorsed the use of the Standardized Computer-based Organized Reporting of EEG (SCORE). This system has many advantages, but only some concerns have been investigated so far. This study aimed to assess the end-users acceptability of this proposed EEG report format. A 16-item electronic survey was sent to physicians who use EEG services of a medical diagnosis clinic. Physicians had been receiving the EEG reports in free-text formats from the same three board-certified electroencephalographers for the past three years. In January 2019, the report changed to the SCORE format. The survey assessed five main topics: physician information and historical use of EEG; personal preferences; comparative aspects of the formats; impact of the new format on clinical decision-making; and satisfaction. Thirty-two of 52 have responded to the survey (61%). On average, 81% of the responders have received enough reports with the new format to reliably complete the survey. Every responder prefers the standardized compared to the free-text format. Twenty-five responders like the inclusion of the head model, and interestingly, five suggest including another legend to differentiate "slow activity" from "other abnormal activity". Virtually all responders would recommend the new format, but one-third read only the conclusion. Our findings suggest high acceptability of this standardized report format. Despite the limitations of this study, we hope these findings contribute to the improvement and expansion of standardized EEG reporting systems.

Yield of Sleep Deprivation EEG in Suspected Epilepsy. A Retrospective Study.

Background. Sleep is an activation procedure and is considered the most potent and best-documented modulator of seizures and interictal epileptiform discharges (IEDs) on electroencephalogram (EEG). The precise role of sleep deprivation in the diagnostic process of epilepsy has not been fully clarified after more than 50 years of use. Sleep deprivation is a procedure that is accompanied by discomfort for patients and their families. Therefore, an accurate indication according to each patient-specific characteristic is needed. This study aims to assess the effectiveness of sleep deprivation EEG in the diagnostic process of patients with suspected epilepsy in our center. Methods. We included patients with a first unprovoked seizure and patients with paroxysmal events suspecting seizures who underwent a sleep deprivation EEG (sdEEG) or routine EEG (rEEG). All patients were subsequently classified with confirmed epilepsy or not. Results. We included 460 patients. The group with sdEEG consisted of 115 patients, while the group with rEEG comprised 345 patients. In the sdEEG group, 19 patients (17%) were confirmed with epilepsy, of which 17 presented interictal epileptiform discharges (IEDs). For the rEEG group, 66 patients (19%) were confirmed with epilepsy, of which 63 presented IEDs. The difference was not statistically significant. Conclusion. Our study failed to find a difference in the yield of sleep deprivation versus routine EEG in patients with epilepsy, but there are many significant confounders/sample biases that limit the generalizability of the findings, particularly to the majority of adult practices.

Sesgo de muestreo y sus implicaciones en la evaluación a personas con riesgo genético de padecer esquizofrenia / Sampling bias and its implications in the evaluation of the population with genetic risk for schizophrenia

La esquizofrenia es considerada como un trastorno mental heterogéneo que abarca amplios rangos de expresión perceptiva, cognoscitiva, emocional, funcional, estructural y del comportamiento, que además se vincula a una importante susceptibilidad genética. Es por ello que investigar sobre esta enfermedad implique seleccionar cuidadosamente a la población de estudio para un adecuado análisis y generalización de los resultados. Este trabajo se propone exponer y discutir diversos sesgos de muestreo basados en evidencias empíricas que resultan, esencialmente, de la inclusión indiscriminada y generalizada de individuos en riesgo y de pacientes con esquizofrenia y/o trastornos relacionados, intentando proponer criterios de selección muestral más estrictos que garanticen una generalización confiable de los resultados. Consecuentemente, reflexionamos en particular sobre la relación entre pacientes con esquizofrenia y sus familiares de primer grado, debido a su similitud genética y las ventajas que esta ofrece para evaluar diversos factores ambientales vinculados a la aparición de la enfermedad

Schizophrenia is considered a heterogeneous mental disorder that encompasses wide ranges of perceptual, cognitive, emotional, functional, structural, and behavioural expressions, which is also associated with significant genetic susceptibility. For this reason, research on this disease involves carefully selecting the study population to perform an adequate analysis and generalisation of the results. This paper proposes to present and discuss various sampling biases based on empirical evidence that mainly result from the indiscriminate and widespread inclusion of at-risk individuals and patients with schizophrenia and/or related disorders, and at the same time trying to propose more stringent sample selection criteria that guarantee reliable results. Consequently, particularly focus is made on the relationship between patients with schizophrenia and their first-degree relatives, due to their genetic similarity and the advantages it offers to evaluate various environmental factors linked to the onset of the disease

Type-1 diabetes shapes working memory processing strategies.

BACKGROUND: Type 1 diabetes (T1D) is a metabolic disorder characterized by recurrent hypo- and hyperglycemic episodes, whose clinical development has been associated with cognitive and working memory (WM) deficits. OBJECTIVE: To contrast quantitative electroencephalography (qEEG) measures between young patients with T1D and healthy controls while performing a visuospatial WM task with two memory load levels and facial emotional stimuli. METHODS: Four or five neutral or happy faces were sequentially and pseudo-randomly presented in different spatial locations, followed by subsequent sequences displaying the reversed spatial order or any other. Participants were instructed to discriminate between these two alternatives during EEG recording. RESULTS: A significant increase in the absolute power of the delta and theta bands, distributed mainly over the frontal region was found during task execution, with a slight decrease of alpha band power in both groups but mainly in control individuals. However, these changes were more pronounced in the T1D patients, and reached their maximum level during the WM encoding phase, even on trials with the lower memory load. In contrast, changes seemed to occur more gradually in controls and results differed significantly only on the trials with the higher WM load. CONCLUSIONS: These results reflect adaptive WM-processing mechanisms in which cognitive strategies have evolved in T1D patients in order to meet task demands.

The supramarginal and angular gyri underlie orthographic competence in Spanish language.

Orthographic competence allows automatic word recognition and reading fluency. To elucidate how the orthographic competence in Spanish-speaking adults might affect the neurofunctional mechanisms of visual word recognition, 32 young adults equally divided in two groups (HSS: High Spelling Skills, and LSS: Low Spelling Skills) were evaluated using fMRI methods, while they performed an orthographic recognition task involving pseudohomophones. HSS achieved significantly more correct responses and lower reaction times than LSS. Interestingly, LSS showed greater activation in the left angular and supramarginal regions with increased bilateral activation pattern in the inferior frontal gyrus, and the anterior temporal and posterior parietal regions. In contrast, HSS showed a more left-lateralized pattern over these regions along with higher activation of the anterior cingulated gyrus for misspelled words. Results suggest that the differences found in cortical activation patterns might be explained by the higher degree of specialization for word recognition in HSS, a group of participants that due to their greater orthographic skills require less engagement of processing resources to succeed in the task.

Corregistro de la actividad eléctrica cerebral y oculomotora: una alternativa para la investigación en dislexia / Simultaneous recording of electrical brain activity and eye movements: an alternative for research into dyslexia

La dislexia es uno de los trastornos del desarrollo más comunes en la etapa escolar y afecta aproximadamente del 5 a 15% de la población. La comprensión en «tiempo real» de un texto requiere del procesamiento de la información visual entrante a través de una compleja serie de fijaciones cortas de la mirada y movimientos sacádicos de los ojos, así como de la recuperación, actualización e integración de los elementos almacenados en la memoria. Esto ha provocado que numerosas investigaciones hayan hecho un gran uso de 2 métodos en particular para su estudio: los potenciales cerebrales relacionados a eventos (PRE) y el rastreo ocular (RO). Sin embargo, los resultados todavía son muy variables y, por tanto, el origen de la dislexia, desde el punto de vista neurobiológico, continúa siendo aún un tema muy debatido. En este trabajo se realiza una revisión exhaustiva de la literatura donde se abordan los hallazgos de los diferentes estudios neurofisiológicos publicados en el tema, así como sus limitaciones. Luego se analiza la factibilidad del registro simultáneo de la actividad eléctrica cerebral y los movimientos oculares mediante la revisión detallada de los aspectos metodológicos a considerar. Por último, se fundamentan las posibles ventajas de este enfoque para los estudios de la lectura, así como sus aplicaciones potenciales en la investigación en dislexia (AU)

Dyslexia is one of the most common developmental disorders at school age and affects approximately 5-15% of the population. Reading is a complex cognitive task and its comprehension requires the processing of visual input across a complex series of brief fixation pauses and saccadic eye movements, as well as retrieving, updating, and integrating contents of memory. This has led to current research making heavy use of two methods: recording eye movement (EMs) and event-related brain potentials (ERPs). However, results are still equivocal, and therefore, the neurobiology of dyslexia remains hotly debated. This paper presents a comprehensive review of the literature in which the findings of different neurophysiological studies published on the subject are addressed, as well as their limitations. The feasibility of simultaneously recording electrical brain activity and eye movements is then analysed by a detailed review of methodological challenges to consider. Finally, the possible benefits of this approach to reading studies and its potential applications in research into dyslexia are described (AU)

Feedback-Related ERP Components Are Modulated by Social Distance during Non-Contingent Evaluation of Someone Else's Performance.

Performance monitoring depends on cortical structures that are also activated in vicarious monitoring. While many experiments have shown that vicarious and on-line monitoring have a similar basis, most such experiments have focused on simple tasks. In order to assess the effect of non-contingent feedback on vicarious monitoring, 23 young volunteer adults were evaluated: in one session, they performed a rule-based category formation task, receiving no feedback on their performance. In a second session, Event Related Potentials (ERPs) were obtained while participants passively reviewed performances attributed to themselves and peers they had previously rated as either socially close or distant. Feedback Related Negativity (FRN) and Feedback Related P300 (fP300) components were analyzed with respect to feedback valence and agent. Results show that both components can be elicited through non-contingent feedback related to prior performance. In addition, FRN waves are modulated by the valence of the feedback, and fP300 is modulated by the agent to whom performance feedback is attributed. This experiment constitutes a novel approach to the evaluation of ERP correlates of vicarious monitoring through non-contingent feedback and its relations to empathy processing.

Decision Making in Social Context in Patients with Suicide Attempt History.

Decision making has been found to be altered in suicide attempters, but little is known of their performance in social contexts. Twenty-seven depressed suicide attempters (DSA), 25 nonsuicidal depressed patients (DP), and 60 healthy participants (HC) were evaluated by a decision-making task in social context. Results indicated DSA and DP obtained lower gains and invested more money with angry partners. DSA were found to invest less money than DP and HC with happy partners. DSA showed insensitivity toward rewards/punishment contingency, and they did not use the socioemotional stimuli to guide their decisions.

Comparisons of numerical magnitudes in children with different levels of mathematical achievement. An ERP study.

The ability to map between non-symbolic and symbolic magnitude representations is crucial in the development of mathematics and this map is disturbed in children with math difficulties. In addition, positive parietal ERPs have been found to be sensitive to the number distance effect and skills solving arithmetic problems. Therefore we aimed to contrast the behavioral and ERP responses in children with different levels of mathematical achievement: low (LA), average (AA) and high (HA), while comparing symbolic and non-symbolic magnitudes. The results showed that LA children repeatedly failed when comparing magnitudes, particularly the symbolic ones. In addition, a positive correlation between correct responses while analyzing symbolic quantities and WRAT-4 scores emerged. The amplitude of N200 was significantly larger during non-symbolic comparisons. In addition, P2P amplitude was consistently smaller in LA children while comparing both symbolic and non-symbolic quantities, and correlated positively with the WRAT-4 scores. The latency of P3 seemed to be sensitive to the type of numerical comparison. The results suggest that math difficulties might be related to a more general magnitude representation problem, and that ERP are useful to study its timecourse in children with different mathematical skills.

Emotional content of stimuli improves visuospatial working memory.

Processing and storage in visuospatial working memory (VSWM) seem to depend on attention-based mechanisms. In order to explore the effect of attention-attractive stimuli, such as emotional faces on VSWM performance, ERPs were obtained from 20 young adults while reproducing spatial sequences of six facial (happy and neutral) and non-facial control stimuli in inverse order. Behavioral performances revealed that trials with happy facial expressions resulted in a significantly higher amount of correct responses. For positive emotional facial stimuli, N170 amplitude was higher over right temporo-parietal regions, while P2 amplitude was higher over frontal and lower over parietal regions. In addition, LPP amplitude was also significantly higher for this type of stimuli. Both behavioral and electrophysiological results support the notion of the domain-general attention-based mechanism of VSWM maintenance, in which spatial to-be-remembered locations might be influenced by the emotional content of the stimuli.

Orthographic recognition in late adolescents: an assessment through event-related brain potentials.

Reading speed and efficiency are achieved through the automatic recognition of written words. Difficulties in learning and recognizing the orthography of words can arise despite reiterative exposure to texts. This study aimed to investigate, in native Spanish-speaking late adolescents, how different levels of orthographic knowledge might result in behavioral and event-related brain potential differences during the recognition of orthographic errors. Forty-five healthy high school students were selected and divided into 3 equal groups (High, Medium, Low) according to their performance on a 5-test battery of orthographic knowledge. All participants performed an orthographic recognition task consisting of the sequential presentation of a picture (object, fruit, or animal) followed by a correctly, or incorrectly, written word (orthographic mismatch) that named the picture just shown. Electroencephalogram (EEG) recording took place simultaneously. Behavioral results showed that the Low group had a significantly lower number of correct responses and increased reaction times while processing orthographical errors. Tests showed significant positive correlations between higher performance on the experimental task and faster and more accurate reading. The P150 and P450 components showed higher voltages in the High group when processing orthographic errors, whereas N170 seemed less lateralized to the left hemisphere in the lower orthographic performers. Also, trials with orthographic errors elicited a frontal P450 component that was only evident in the High group. The present results show that higher levels of orthographic knowledge correlate with high reading performance, likely because of faster and more accurate perceptual processing, better visual orthographic representations, and top-down supervision, as the event-related brain potential findings seem to suggest.

Visual processing in a facial emotional context: an ERP study.

Facial emotional processing can be bypassed when faces are task-irrelevant and attention is diverted, although this effect has not been examined when cognitive task occurs within a facial background. Event-related potential (ERP) measures were obtained to evaluate the influence of different irrelevant facial emotional contexts on a simultaneous "ear-size" detection task performance in five processing contexts: (1) neutral face, (2) happy face, (3) fearful face, (4) facial contour, and (5) non-facial context. Reaction times were longer when visual processing occurred in a facial context, regardless of its emotional content. The context of neutral faces also demonstrated a lower number of correct responses, with fewer incorrect responses found during the presentation of fearful faces compared to the neutral facial context. ERP morphology was similar across all conditions, but ERP amplitude from components for the non-facial context was larger than that of the alternative conditions from 100 to 300 ms, with a similar N170-like potential also observed. The findings suggest that simultaneous irrelevant emotional facial stimuli may affect cognitive processing by altering two temporarily overlapped neural mechanisms: one responsible for earlier face detection, and the other involved in emotional recognition. The first might delay simultaneous cognitive actions by diverting attention, whereas while the latter may enhance the availability of processing resources through the participation of a subcortical pathway.

Análisis cuantitativo del electroencefalograma para confirmar trastorno funcional frontal en niños con trastorno por déficit de atención con hiperactividad / Quantitative electroencephalogram analysis confirms the presence of frontal lobe deficit among attention deficit disorder with hyperactivity children

Antecedentes: En 1997, Barkley postuló un modelo funcional del trastorno por déficit de atención con hiperactividad (TDAH) basado en la presencia de un déficit central que afecta el desempeño de las funciones ejecutivas. Hallazgos neuroanatómicos y neurofisiológicos relacionan la afectación de los lóbulos frontales con los procesos cognitivos y conductuales de sujetos con TDAH. Objetivo: Evaluar electrofisiológicamente la teoría de Barkley (1997). Sujetos y métodos: Se estudiaron niños entre 7 y 11 años de edad con TDAH (subtipo inatento) y un grupo control. Se compararon los registros electroencefalográficos obtenidos durante la ejecución de una tarea de estimación del tiempo (ES) con el estado de reposo con ojos abiertos (RA). Se conformaron 42 matrices con 5 tipos diferentes de datos electroencefalográficos (19 derivaciones: sistema 10/20) en tres condiciones: RA, ES y ES-RA (potencia absoluta y potencia relativa). Se utilizaron dos métodos de clasificación. Resultados: El análisis de varianza reveló diferencias significativas en el cociente de anterioridad bajo la condición ES-RA. La clasificación con análisis discriminante reportó una efectividad superior a 80%, mientras que una nueva propuesta de clasificación lineal realizó una clasificación superior a 80% con sólo dos derivaciones. Conclusión: Los resultados apoyan las hipótesis de Barkley y sugieren el uso del cociente de anterioridad referido a temporales para caracterizar electrofisiológicamente el TDAH en niños en edad escolar.

BACKGROUND: The Attention Deficit Disorder with Hyperactivity (ADDH) Barkley model predicts concomitant deficits in working memory and in the development of a sense of time as a consequence of poor behavioral inhibition. Objective: To evaluate electrophysiologically Barkley's theory (1997). SUBJECTS AND METHODS: We studied the electroencephalogram (EEG) of fifteen right-handed, normal limit IQ ADDH children (inattentive subtype), aged 7-11 years, and a control group. Subjects were studied at rest, with the eyes open (RO) while performing a time estimation task (ET). Forty-two data matrices were analyzed in three conditions: RO, ET and ET-RO, to assess broad-band spectral parameters; the anteriority, temporal-referenced and laterality quotients (Aq, Aqt and Lq, respectively); and the theta/alpha and theta/beta ratios. RESULTS: Analyses of variance revealed significant differences for ES-RA, in absolute (Aq &Aqt) and relative powers (Aq). Discriminant function analysis was able to predict group membership with an accuracy over 80%, but it decreased slightly when the leave-one-out method was applied Linear discrimination based on right hemisphere Aqt values showed the highest discrimination accuracy. CONCLUSIONS: These results support Barkley's theory, suggesting further evaluation of the temporal-referenced anteriority quotient as a promising electrophysiological tool for the diagnosis and follow up of ADDH children.

[Quantitative electroencephalogram analysis confirms the presence of frontal lobe deficit among attention deficit disorder with hyperactivity children]. / Análisis cuantitativo del electroencefalograma para confirmar trastorno funcional frontal en niños con trastorno por déficit de atención con hiperactividad.

BACKGROUND: [corrected] The Attention Deficit Disorder with Hyperactivity (ADDH) Barkley model predicts concomitant deficits in working memory and in the development of a sense of time as a consequence of poor behavioral inhibition. OBJECTIVE: To evaluate electrophysiologically Barkley's theory (1997). SUBJECTS AND METHODS: We studied the electroencephalogram (EEG) of fifteen right-handed, normal limit IQ ADDH children (inattentive subtype), aged 7-11 years, and a control group. Subjects were studied at rest, with the eyes open (RO) while performing a time estimation task (ET). Forty-two data matrices were analyzed in three conditions: RO, ET and ET-RO, to assess broad-band spectral parameters; the anteriority, temporal-referenced and laterality quotients (Aq, Aqt and Lq, respectively); and the theta/alpha and theta/beta ratios. RESULTS: Analyses of variance revealed significant differences for ES-RA, in absolute (Aq &Aqt) and relative powers (Aq). Discriminant function analysis was able to predict group membership with an accuracy over 80%, but it decreased slightly when the leave-one-out method was applied Linear discrimination based on right hemisphere Aqt values showed the highest discrimination accuracy. CONCLUSIONS: These results support Barkley's theory, suggesting further evaluation of the temporal-referenced anteriority quotient as a promising electrophysiological tool for the diagnosis and follow up of ADDH children.

Relationship between resting alpha activity and the ERPs obtained during a highly demanding selective attention task.

In spite of previous reports on the relationship between ongoing EEG and ERPs, there remains a lack of agreement on the nature of their nexuses. The aim of the present study was to evaluate the relationship between resting EEG and the ERP components in two groups of healthy subjects with different levels of performance in a highly demanding selective visual attention task. Young adults were classified according to the amount of their correct responses in the task, into high (HP; averaged hits (AH): 86%) and low performance groups (LP; AH: 59%). EEG was recorded during rest, prior to task performance and absolute (AP) and relative power (RP), as well as inter- (rTER) and intrahemispheric (rTRA) correlation were calculated. ERPs during task performance were also obtained and their amplitude and latency measures were assessed. Results showed that individuals with better behavioral performance had a higher synchronization between both hemispheres during rest as well as higher amplitude and shorter latencies of N2 and P3. Principal Component Analysis revealed that alpha2 AP and RP were inversely related to P2 and N2 latency. Higher values of alpha1 and alpha2 rTER were clustered with higher P3 amplitude and shorter reaction time. In conclusion, the differences in the cortical organization of HP and LP at rest (EEG) seem to be associated to the way the brain reacts during information processing (ERPs).

Hypercalculia in savant syndrome: central executive failure?

BACKGROUND: The existence of outstanding cognitive talent in mentally retarded subjects persists as a challenge to present knowledge. We report the case of a 16-year-old male patient with exceptional mental calculation abilities and moderate mental retardation. METHODS: The patient was clinically evaluated. Data from standard magnetic resonance imaging (MRI) and two 99mTc-ethyl cysteine dimer (ECD)-single photon emission computer tomography (SPECT) (in resting condition and performing a mental calculation task) studies were analyzed. RESULTS: Main neurologic findings were brachycephalia, right-side neurologic soft signs, obsessive personality profile, low color-word interference effect in Stroop test, and diffuse increased cerebral blood flow during calculation task in 99mTc-ECD SPECT. MRI showed anatomical temporal plane inverse asymmetry. CONCLUSIONS: Evidence appears to support the hypothesis that savant skill is related to excessive and erroneous use of cognitive processing resources instigated by probable failure in central executive control mechanisms.

Event related brain potentials to semantically incongruent words in children of different ages

In this study, developmental changes of N400 elicited by a simple paradigm to semantic incongruity were examined. Subjects were divided in three different age groups and education levels: Group I (first grade) = 7-8 years, n=10; Group II (third grade) = 9-10 years, n=10; and Group III (sith grade)= 11-12 years, n=10. EEG activity was recorded from 8 monopolar sites referred to linked earlobes. Data showed that the amplitude of the N400 like component did not change significantly from first to sith grade, although the onset latency appeared to be shorter in older children. No significant latency and amplitude changes were found among groups