Cognitive evoked potentials in obstructive sleep apnea syndrome: a review of the literature

Cognitive functions may be altered in patients with obstructive sleep apnea syndrome (OSAS) and it has been proposed that vigilance and attention changes play a fundamental role in all aspects of cognitive deficits noted in this disease. The use of event-related potentials (ERPs) is a high-time resolution technique that can be used to explore the presence of cognitive dysfunction. We review 23 empirical articles on ERPs in OSAS in order to contribute to the clarification of the pattern of cognitive deficits that are specific to this disease and to see whether there might be an improvement of abnormal psychophysiological findings with continuous positive airway pressure (CPAP) treatment. We conclude that ERP studies have contributed to demonstrating changes in cognitive attentive processing in OSAS, mainly in association with altered functioning of the prefrontal cortex, and that CPAP treatment may improve vigilance and attention and generally improve cerebral information processing in these patients. The remaining deficits during sufficient CPAP therapy may, however, reflect irreversible hypoxic cerebral damage.     

Event-related-potential low-resolution brain electromagnetic tomography (ERP-LORETA) suggests decreased energetic resources for cognitive processing in narcolepsy

OBJECTIVE: Event-related potentials (ERPs) are sensitive measures of both perceptual and cognitive processes. The aim of the present study was to identify brain regions involved in the processes of cognitive dysfunction in narcolepsy by means of ERP tomography. METHODS: In 17 drug-free patients with narcolepsy and 17 controls, ERPs were recorded (auditory odd-ball paradigm). Latencies, amplitudes and LORETA sources were determined for standard (N1 and P2) and target (N2 and P300) ERP components. Psychometry included measures of mental performance, affect and critical flicker fusion frequency (CFF). RESULTS: In the ERPs patients demonstrated delayed cognitive N2 and P300 components and reduced amplitudes in midline regions, while N1 and P2 components did not differ from controls. LORETA suggested reduced P300 sources bilaterally in the precuneus, the anterior and posterior cingulate gyri, the ventrolateral prefrontal cortex and the parahippocampal gyrus. In psychometry, patients demonstrated deteriorated mood, increased trait anxiety, decreased CFF and a trend toward reduced general verbal memory and psychomotor activity. CONCLUSIONS: Narcoleptic patients showed prolonged information processing, as indexed by N2 and P300 latencies and decreased energetic resources for cognitive processing. SIGNIFICANCE: Electrophysiological aberrations in brain areas related to the 'executive attention network' and the 'limbic system' may contribute to a deterioration in mental performance and mood at the behavioral level.     

Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review

ObjectiveSystematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations).MethodsPubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards.ResultsERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients.ConclusionsWhile there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms.SignificanceThe review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.     

ERPs and Eye Movements Reflect Atypical Visual Perception in Pervasive Developmental Disorder

Many studies of eye tracking or event-related brain potentials (ERPs) in subjects with Pervasive Developmental Disorder (PDD) have yielded inconsistent results on attentional processing. However, recent studies have indicated that there are specific abnormalities in early processing that are probably related to perception. ERP amplitudes in response to visual stimuli, measured above the occipital (modality-specific) cortex, are reported to be abnormally small in patients with PDD, and the abnormal visual processing is possibly associated with the spatial visual frequency content of stimuli. It is suggested that subjects with PDD show abnormal activation of visual pathways dedicated to the processing of high and low spatial frequencies.     

Event Related Potentials in the Understanding of Autism Spectrum Disorders: An Analytical Review

In this paper we critically review the literature on the use of event related potentials (ERPs) to elucidate the neural sources of the core deficits in autism. We review auditory and visual ERP studies, and then review the use of ERPs in the investigation of executive function. We conclude that, in autism, impairments likely exist in both low and higher level auditory and visual processing, with prominent impairments in the processing of social stimuli. We also discuss the putative neural circuitry underlying these deficits. As we look to the future, we posit that tremendous insight can be gained by applying ERPs to the definition of endophenotypes, which, in turn, can facilitate early diagnosis and the creation of informed interventions for children with autism.     

Functional involvement of cerebral cortex in human narcolepsy

Abstract The pathophysiology of human narcolepsy is still poorly understood. The hypoactivity of some neurotransmitter systems has been hypothesised on the basis of the canine model. To determine whether narcolepsy is associated with changes in excitability of the cerebral cortex, we assessed the excitability of the motor cortex with transcranial magnetic stimulation (TMS) in 13 patients with narcolepsy and in 12 control subjects. We used several TMS paradigms that can provide information on the excitability of the motor cortex. Resting and active motor thresholds were higher in narcoleptic patients than in controls and intracortical inhibition was more pronounced in narcoleptic patients. No changes in the other evaluated measures were detected. These results are consistent with an impaired balance between excitatory and inhibitory intracortical circuits in narcolepsy that leads to cortical hypoexcitability. We hypothesise that the deficiency of the excitatory hypocretin/orexin-neurotransmitter-system in narcolepsy is reflected in changes of cortical excitability since circuits originating in the lateral hypothalamus and in the basal forebrain project widely to the neocortex, including motor cortex. This abnormal excitability of cortical networks could be the physiological correlate of excessive daytime sleepiness and it could be the substrate for allowing dissociated states of wakefulness and sleep to emerge suddenly while patients are awake, which constitute the symptoms of narcolepsy.     

Event‐related potential measures of executive functioning from preschool to adolescence

Executive functions are a collection of cognitive abilities necessary for behavioural control and regulation, and are important for school success. Executive deficits are common across acquired and developmental disorders in childhood and beyond. This review aims to summarize how studies using event‐related potential (ERP) can provide insight into mechanisms underpinning how executive functions develop in children from preschool to adolescence. We specifically focus on ERP components that are considered to be well‐established markers of executive functioning, including the ability to resist distraction (inhibition, N200), hold scenes in mind (visuospatial working memory, contralateral delay activity), attend to specific stimuli (information processing, P300), follow rules (response monitoring, error‐related negativity [ERN], and error‐related positivity [Pe]), and adjust to feedback (outcome monitoring, feedback‐related negativity). All of these components show developmental changes from preschool to adolescence, in line with behavioural and neuroimaging findings. These ERP markers also show altered developmental trajectories in the context of atypical executive functions. As an example, deficits in executive function are prominently implicated in attention‐deficit–hyperactivity disorder. Therefore, this review highlights ERP studies that have investigated the above ERP components in this population. Overall, ERPs provide a useful marker for the development and dysfunction of executive skills, and provide insight into their neurophysiological basis.     

A critical review of the contribution of eye movement recordings to the neuropsychology of obsessive compulsive disorder

Jaafari N, Rigalleau F, Rachid F, Delamillieure P, Millet B, Olié J.‐P, Gil R, Rotge J.‐Y, Vibert N. A critical review of the contribution of eye movement recordings to the neuropsychology of obsessive compulsive disorder. Objective: Dysfunctions of saccadic and/or smooth pursuit eye movements have been proposed as markers of obsessive compulsive disorder (OCD), but experimental results are inconsistent. The aim of this paper was to review the literature on eye movement dysfunctions in OCD to assess whether or not saccades or smooth pursuit may be used to diagnose and characterize OCD. Method: Literature was searched using PubMed, ISI Web of Knowledge, and PsycINFO databases for all studies reporting eye movements in adult patients suffering from OCD. Results: Thirty‐three articles were found. As expected, eye movements of the patients with OCD were mostly assessed with simple oculomotor paradigms involving saccadic and/or smooth pursuit control. In contrast to patients with schizophrenia, however, patients with OCD only displayed rather unspecific deficits, namely slight smooth pursuit impairments and longer response latencies on antisaccade tasks. There was no relationship between these deficits and the severity of patients’ symptoms. Interestingly, eye movements of the patients with OCD were almost never recorded during more complex cognitive tasks. Conclusion: As in schizophrenia and autism, eye movement recordings during more complex tasks might help to better characterize the cognitive deficits associated with OCD. Such recordings may reveal specific OCD‐related deficits that could be used as reliable diagnostic and/or classification tools.     

Cognitive and motor event-related potentials in Tourette syndrome and tic disorders: A systematic review

ObjectivesTourette syndrome (TS) patients face various cognitive and motor impairments. Event-related potentials (ERP) constitute an effective way to investigate the neural correlates of those functional impairments. Various components have been assessed among TS patients, with a wide variety of paradigms. This systematic review aimed to evaluate the portrait of ERP components in TS patients, and to understand the factors leading to discrepancies across studies.MethodsA literature search was performed in Embase, PsycINFO, Pubmed, and Web of Science, to identify studies that conducted ERP experiments among TS patients. Of the 372 unique records identified, 47 met inclusion criteria and were included in our systematic review.ResultsVarious ERP particularities were reported among included studies. Many discrepancies exist, but impairments in motor-related potentials and contingent negative variation seem constant across studies. Divergent findings point toward a possibly reduced P3b during oddball tasks.ConclusionsERPs offer an insightful investigation into the cognitive and motor functions of TS patients. Future studies should always control for confounding factors such as comorbidity, age, or medication status.SignificanceThis is the first systematic review of ERP in TS patients. Motor-related and slow cortical potentials could constitute electrophysiological markers of TS.     

Event‐related potential and eye tracking evidence of the developmental dynamics of face processing

Although the wide neural network and specific processes related to faces have been revealed, the process by which face‐processing ability develops remains unclear. An interest in faces appears early in infancy, and developmental findings to date have suggested a long maturation process of the mechanisms involved in face processing. These developmental changes may be supported by the acquisition of more efficient strategies to process faces (theory of expertise) and by the maturation of the face neural network identified in adults. This study aimed to clarify the link between event‐related potential (ERP) development in response to faces and the behavioral changes in the way faces are scanned throughout childhood. Twenty‐six young children (4–10 years of age) were included in two experimental paradigms, the first exploring ERPs during face processing, the second investigating the visual exploration of faces using an eye‐tracking system. The results confirmed significant age‐related changes in visual ERPs (P1, N170 and P2). Moreover, an increased interest in the eye region and an attentional shift from the mouth to the eyes were also revealed. The proportion of early fixations on the eye region was correlated with N170 and P2 characteristics, highlighting a link between the development of ERPs and gaze behavior. We suggest that these overall developmental dynamics may be sustained by a gradual, experience‐dependent specialization in face processing (i.e. acquisition of face expertise), which produces a more automatic and efficient network associated with effortless identification of faces, and allows the emergence of human‐specific social and communication skills.     

Cognitive impairments in patients with first episode psychosis: The relationship between neurophysiological and neuropsychological assessments

Cognitive deficits in schizophrenia have been widely reported. Neurophysiological and neuropsychological assessments have been conducted to study these impairments. Event-related potentials (ERPs) are relevant markers of cognitive deficits in schizophrenia, and reductions in specific ERP components have been found. The MATRICS Consensus Cognitive Battery (MCCB) was developed to obtain a consensus battery for the assessment of cognitive deficits in schizophrenia. Here, we aimed to study modulations of several ERP components in first episode psychosis (FEP). We also examined neuropsychological deficits using the MCCB, and correlations between ERP and MCCB impairments. Thirty-eight FEP patients were compared to thirty-eight healthy controls. The following ERP components were examined: P1, N1, MMN, P2, early-P3 and late-P3. We used an auditory three-stimulus oddball paradigm, with standard (60%), target (20%) and distractor (20%) stimuli. FEP patients showed significantly lower amplitudes of P2, early-P3 and late-P3 components. FEP patients also showed significant deficits in all the MCCB cognitive domains. Finally, correlational analyses found strong associations between amplitudes of P2, early-P3 and late-P3 components and MCCB tests for attention and speed of processing. These findings indicate that deficits in late auditory ERP components are present in FEP, whereas early components are preserved. These reductions in late ERP components were related to attentional deficits in FEP as assessed by MCCB. These findings indicate that MCCB is a valid battery for studying cognitive impairments in the initial stages of schizophrenia, and highlight the utility of converging neurophysiological and neuropsychological measures to examine attentional impairments in schizophrenia.     

Event-related brain dynamics

Event-related potentials (ERPs) provide evidence of a direct link between cognitive events and brain electrical activity in a wide range of cognitive paradigms. It has generally been held that an ERP is the result of a set of discrete stimulus-evoked brain events. A recent study, however, provides new evidence to suggest that some ERP components might be generated by stimulus-induced changes in ongoing brain dynamics. This is consistent with views emerging from several neuroscientific fields, suggesting that phase synchronization of ongoing rhythms across different spatio-temporal scales mediates the functional integration necessary to perform higher cognitive tasks.     

Cognitive event-related potentials: useful clinical information in Alzheimer's disease

Cognitive event-related potentials (ERPs) have been used as a marker of cognitive function in patients with psychiatric and neurological disorders. In particular, the P300 potential has been widely utilized to study dementia and aging, because the P300 ERP component is easily observed and reflects attention and memory processing. However, the relationship between parameters of the P300 potential and the severity or type of cognitive impairment in patients with Alzheimer's disease (AD) remains controversial. Because specific and effective anti-dementia treatments have recently become available for AD, more useful information is needed about the clinical aspects of this disease, including methods of making an accurate and early diagnosis, differentiation from vascular dementia and other degenerative dementias, assessment of severity, assessment of disease progression, evaluation of the response to treatment, and prediction of the prognosis. This mini-review described new discoveries on recent clinical application of ERPs in AD with respect to the above-mentioned areas. Although the definition of normal ERP values and the most appropriate method of ERP recording in AD patients have not been well defined, recent findings suggest that ERP analysis may be a clinically useful, inexpensive, noninvasive, and reliable method of assessing AD.     

Systematic review of cognitive event related potentials in euthymic bipolar disorder

Cognitive deficits are critical features of bipolar disorder (BD), greatly impacting quality of life. The aim is to systematically review and critically evaluate underlying event related potential (ERP) features in euthymic BD relating to differences in sensory processes, attention, inhibition and conflict monitoring compared with healthy controls. 911 unique articles were identified using the PubMed database and 14 studies met the inclusion criteria. Individuals with BD in a euthymic state have reduced P50 sensory gating and reduced P100 amplitudes compared with healthy controls. Many studies demonstrated reduced P300 amplitudes and normal P300 latencies in BD. In addition, reduced NoGo N2 and abnormal NoGo P3 activity were observed in BD. Finally, there is some evidence of reduced error-related negativity amplitudes in BD. Importantly, ERP modulations vary with stimulus factors and clinical profile. The functional significance of these findings and clinical implications are discussed. ERP differences in BD arise at various stages of cognitive processing, specifically in early auditory and visual processing, attention allocation, context updating, inhibition and conflict monitoring. Treating these deficits and their underlying neurobiological disturbances corresponding to abnormal performance on cognitive tasks may aid functional remission. This knowledge might enable personalized treatment interventions targeting specific cognitive deficits.     

The Madrid card sorting test (MCST): a task switching paradigm to study executive attention with event-related potentials

Event-related potentials (ERPs) provide valuable information about the fast brain dynamics subserving cognitive functions such as attention and working memory. Most ERP studies employ cognitive paradigms with a fixed task-set (i.e., press a button to coloured targets), but few have measured ERPs time-locked to shifts in set using a task-switching paradigm. The Madrid card sorting test (MCST) is a dual task protocol in which feedback cues signal unpredictable shifts in set (i.e., from 'sort cards by colour' to 'sort cards by shape'). This protocol allows for an integrated analysis of ERPs to both feedback cues and target card events, providing separate ERP features for the shifting, updating, and rehearsal of attention sets in working memory. Two of these ERP indices are the frontal and posterior aspects of the P300 response. Feedback cues that direct a shift in set also elicit a frontally distributed P3a potential (300-400 ms). Instead, target card events evoke increasingly larger posterior P3b (350-600 ms) activity as the new task set becomes gradually rehearsed. The observed modulations in the frontal and posterior aspects of the P300 response system are interpreted from current models of prefrontal cortex function in the executive control of attention.     

Neuroelectrical signs of selective attention to color in boys with attention-deficit hyperactivity disorder

In order to gain insight into the functional and macroanatomical loci of visual selective processing deficits that may be basic to attention-deficit hyperactivity disorder (ADHD), the present study examined multi-channel event-related potentials (ERPs) recorded from 7- to 11-year-old boys clinically diagnosed as having ADHD (n=24) and age-matched healthy control boys (n=24) while they performed a visual (color) selective attention task. The spatio-temporal dynamics of several ERP components related to attention to color were characterized using topographic profile analysis, topographic mapping of the ERP and associated scalp current density distributions, and spatio-temporal source potential modeling. Boys with ADHD showed a lower target hit rate, a higher false-alarm rate, and a lower perceptual sensitivity than controls. Also, whereas color attention induced in the ERPs from controls a characteristic early frontally maximal selection positivity (FSP), ADHD boys displayed little or no FSP. Similarly, ADHD boys manifested P3b amplitude decrements that were partially lateralized (i.e., maximal at left temporal scalp locations) as well as affected by maturation. These results indicate that ADHD boys suffer from deficits at both relatively early (sensory) and late (semantic) levels of visual selective information processing. The data also support the hypothesis that the visual selective processing deficits observed in the ADHD boys originate from deficits in the strength of activation of a neural network comprising prefrontal and occipito-temporal brain regions. This network seems to be actively engaged during attention to color and may contain the major intracerebral generating sources of the associated scalp-recorded ERP components.     

Information processing deficits in head injury assessed with ERPs reflecting early and late processing stages

ERPs provide informative measures of slowed information processing in head injury. While several studies have reported changes in long latency ERPs (N2, P3) in head injury, the data on early ERP components related to attention selection are inconclusive. The problem may be partly methodological because the standard oddball paradigm does not give an adequate basis for discriminating components contributing to the N1 and P2 waveforms. Following a suggestion by Garcia-Larrea et al. [10: Garcia-Larrea L, Lukasziewicz A-C, Maugière F. Revisiting the oddball paradigm. Non-target vs neutral stimuli and the evaluation of ERP attention effects. Neuropsychologia 1992;30:723-741] we used an extended oddball paradigm to study measures of early processing (N1-average, P250) as well as conventional cognitive ERPs (N1, P2, N2, P3) in a group of head injured patients and controls. We found evidence of deficits in early processing of neutral and non-target stimuli in the patient group, and interpret the findings as an indication that the patients are less efficient in terminating processing of irrelevant stimuli. The results further indicate that processing deviations affect both target and non-target stimuli in the oddball paradigm and thus the allocation of attention in the task as a whole.     

Event-related potentials and cognition in Parkinson’s disease: An integrative review

Cognitive impairment is a common non-motor symptom of Parkinson’s disease (PD), but the nature of cognitive changes varies considerably between individuals. According to the dual-syndrome hypothesis, one cluster of patients is characterized by deficits in executive function that may be related to fronto-striatal dysfunction. Other patients primarily show non-frontal cognitive impairments that progress rapidly to PD dementia (PDD). We provide a comprehensive review of event-related potential (ERP) studies to identify ERP measures substantiating the heterogeneity of cognitive impairment in PD. Our review revealed evidence for P3b and mismatch-negativity alterations in PDD, but not in non-demented PD, indicating that alterations of these ERPs constitute electrophysiological markers for PDD. In contrast, ERP correlates of executive functions, such as NoGo-P3, N2, and error(-related) negativity (N_e/ERN), appear to be attenuated in non-demented PD patients in a dopamine-dependent manner. Hence, ERP measures confirm and yield distinct electrophysiological markers for the heterogeneity of cognitive impairment in PD. We discuss limitations and open questions of the ERP approach and provide directions and predictions for future ERP research.     

Visual information processing in dyslexic children.

OBJECTIVE: Several studies presented evidence for magnocellular deficits in dyslexics both in behavioural as well as in electrophysiological data of local electrode sites. We investigated two well-known paradigms (motion-onset and random-dot-kinematogram) with regard to global electrophysiological parameters. METHODS: Twenty-one-channel event-related potentials (ERPs) of 16 dyslectic and 15 control children were analyzed with reference-independent methods. For each paradigm quasi stable microstates were identified by means of a data-driven segmentation procedure and compared between both groups. RESULTS: Differences in global ERP responses between dyslexic and control children could be found for rapid moving gratings but not for the dot coherence. CONCLUSIONS: Dyslexic children seem to have some highly specific visual deficits in processing moving stimuli. These deficits can be related to the magnocellular system.