The P3a wave: A reliable neurophysiological measure of Parkinson’s disease duration and severity

A study of brain networks associated with Freezing of gait in Parkinson's disease using transfer entropy analysis

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease in the elderly. Freezing of Gait (FOG) is one of the common motor symptoms of PD, but the potential mechanism remains unclear. This study aimed to investigate the changes of brain functional network topology in PD patients with FOG.

METHODS

The resting electroencephalogram (EEG) were acquired from15 PD patients with FOG (PD-FOG), 13 PD patients without FOG (PD-nFOG), and 16 healthy control (HC). Cognitive and motor functions were assessed using subjective scales. The whole-brain functional networks were constructed based on transfer entropy. Transfer entropy was used to analyse the information flow and causality in the network and the network connectivity was analyzed by graph theory. The characteristics of PD-FOG and PD-nFOG were compared by receiver operator characteristic (ROC) curve analysis.

RESULTS

The θ bands brain network of PD-FOG, PD-nFOG and HC group was significantly different (P < 0.05). The average characteristic path length of the θ bands brain network was positively correlated with FOG Questionnaire (FOGQ). PD-FOG and PD-nFOG get high classification accuracy according to this feature. The information inflow in the frontal and occipital lobes and information outflow in the temporal lobe of PD-FOG patients in the θ bands increased significantly.

CONCLUSIONS

The whole-brain functional network characteristics of PD-FOG in the θ bands can serve as potential biomarkers for early diagnosis of PD-FOG. Abnormal information flow of the frontal, occipital, and temporal lobes in the θ bands may be an important factor leading to FOG.

Evoked mid-frontal activity predicts cognitive dysfunction in Parkinson's disease

BACKGROUND

Cognitive dysfunction is a major feature of Parkinson's disease (PD), but the pathophysiology remains unknown. One potential mechanism is abnormal low-frequency cortical rhythms which engage cognitive functions and are deficient in PD. We tested the hypothesis that mid-frontal delta/theta rhythms predict cognitive dysfunction in PD.

METHOD

We recruited 100 patients with PD and 49 demographically similar control participants who completed a series of cognitive control tasks, including the Simon, oddball and interval-timing tasks. We focused on cue-evoked delta (1-4 Hz) and theta (4-7 Hz) rhythms from a single mid-frontal EEG electrode (cranial vertex (Cz)) in patients with PD who were either cognitively normal, with mild-cognitive impairments (Parkinson's disease with mild-cognitive impairment) or had dementia (Parkinson's disease dementia).

RESULTS

We found that PD-related cognitive dysfunction was associated with increased response latencies and decreased mid-frontal delta power across all tasks. Within patients with PD, the first principal component of evoked electroencephalography features from a single electrode (Cz) strongly correlated with clinical metrics such as the Montreal Cognitive Assessment score (r=0.34) and with National Institutes of Health Toolbox Executive Function score (r=0.46).

CONCLUSIONS

These data demonstrate that cue-evoked mid-frontal delta/theta rhythms directly relate to cognition in PD. Our results provide insight into the nature of low-frequency frontal rhythms and suggest that PD-related cognitive dysfunction results from decreased delta/theta activity. These findings could facilitate the development of new biomarkers and targeted therapies for cognitive symptoms of PD.

Task-Related Reorganization of Cognitive Network in Parkinson's Disease Using Electrophysiology

BACKGROUND

Cognitive deficits in Parkinson's disease (PD) patients are well described, however, their underlying neural mechanisms as assessed by electrophysiology are not clear.

OBJECTIVES

To reveal specific neural network alterations during the performance of cognitive tasks in PD patients using electroencephalography (EEG).

METHODS

Ninety participants, 60 PD patients and 30 controls underwent EEG recording while performing a GO/NOGO task. Source localization of 16 regions of interest known to play a pivotal role in GO/NOGO task was performed to assess power density and connectivity within this cognitive network. The connectivity matrices were evaluated using a graph-theory approach that included measures of cluster-coefficient, degree, and global-efficiency. A mixed-model analysis, corrected for age and levodopa equivalent daily dose was performed to examine neural changes between PD patients and controls.

RESULTS

PD patients performed worse in the GO/NOGO task (P < 0.001). The power density was higher in δ and θ bands, but lower in α and β bands in PD patients compared to controls (interaction group × band: P < 0.001), indicating a general slowness within the network. Patients had more connections within the network (P < 0.034) than controls and these were used for graph-theory analysis. Differences between groups in graph-theory measures were found only in cluster-coefficient, which was higher in PD compared to controls (interaction group × band: P < 0.001).

CONCLUSIONS

Cognitive deficits in PD are underlined by alterations at the brain network level, including higher δ and θ activity, lower α and β activity, increased connectivity, and segregated network organization. These findings may have important implications on future adaptive deep brain stimulation. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

EEG-Based Parkinson's Disease Recognition via Attention-Based Sparse Graph Convolutional Neural Network

Parkinson's disease (PD) is a complicated neurological ailment that affects both the physical and mental wellness of elderly individuals which makes it problematic to diagnose in its initial stages. Electroencephalogram (EEG) promises to be an efficient and cost-effective method for promptly detecting cognitive impairment in PD. Nevertheless, prevailing diagnostic practices utilizing EEG features have failed to examine the functional connectivity among EEG channels and the response of associated brain areas causing an unsatisfactory level of precision. Here, we construct an attention-based sparse graph convolutional neural network (ASGCNN) for diagnosing PD. Our ASGCNN model uses a graph structure to represent channel relationships, the attention mechanism for selecting channels, and the L1 norm to capture channel sparsity. We conduct extensive experiments on the publicly available PD auditory oddball dataset, which consists of 24 PD patients (under ON/OFF drug status) and 24 matched controls, to validate the effectiveness of our method. Our results show that the proposed method provides better results compared to the publicly available baselines. The achieved scores for Recall, Precision, F1-score, Accuracy and Kappa measures are 90.36%, 88.43%, 88.41%, 87.67%, and 75.24%, respectively. Our study reveals that the frontal and temporal lobes show significant differences between PD patients and healthy individuals. In addition, EEG features extracted by ASGCNN demonstrate significant asymmetry in the frontal lobe among PD patients. These findings can offer a basis for the establishment of a clinical system for intelligent diagnosis of PD by using auditory cognitive impairment features.

Update on Nonhuman Primate Models of Brain Disease and Related Research Tools

The aging of the population is an increasingly serious issue, and many age-related illnesses are on the rise. These illnesses pose a serious threat to the health and safety of elderly individuals and create a serious economic and social burden. Despite substantial research into the pathogenesis of these diseases, their etiology and pathogenesis remain unclear. In recent decades, rodent models have been used in attempts to elucidate these disorders, but such models fail to simulate the full range of symptoms. Nonhuman primates (NHPs) are the most ideal neuroscientific models for studying the human brain and are more functionally similar to humans because of their high genetic similarities and phenotypic characteristics in comparison with humans. Here, we review the literature examining typical NHP brain disease models, focusing on NHP models of common diseases such as dementia, Parkinson's disease, and epilepsy. We also explore the application of electroencephalography (EEG), magnetic resonance imaging (MRI), and optogenetic study methods on NHPs and neural circuits associated with cognitive impairment.

Developments of possible clinical diagnostic methods for parkinson's disease: event-related potentials

In this study, Event-Related Potential (ERP) analyzes were performed to detect cognitive impairments in PD with Deep Brain Stimulation (DBS). A total of 85 volunteers underwent ERP analysis and neuropsychological testing (NPT) to determine cognitive level. In ERP analyses, prolonged latencies were observed in PD groups. However, patients implanted with DBS showed a decrease in latencies, a decrease in symptoms and statistical improvements in both cognitive and attention skills. Considering all these data, ERP results are promising as a noninvasive method that can be used in both disease status and diagnosis of PD.

Listening with an Ageing Brain - a Cognitive Challenge

Hearing impairment has been recently identified as a major modifiable risk factor for cognitive decline in later life and has been becoming of increasing scientific interest. Sensory and cognitive decline are connected by complex bottom-up and top-down processes, a sharp distinction between sensation, perception, and cognition is impossible. This review provides a comprehensive overview on the effects of healthy and pathological aging on auditory as well as cognitive functioning on speech perception and comprehension, as well as specific auditory deficits in the 2 most common neurodegenerative diseases in old age: Alzheimer disease and Parkinson syndrome. Hypotheses linking hearing loss to cognitive decline are discussed, and current knowledge on the effect of hearing rehabilitation on cognitive functioning is presented. This article provides an overview of the complex relationship between hearing and cognition in old age.

Age-related changes to electroencephalographic markers of visuomotor error processing and learning in prism adaptation

Aging is associated with changes in cognitive function, including declines in learning, memory, and executive function. Prism adaptation (PA) is a useful paradigm to measure changes in explicit and implicit mechanisms of visuo-motor learning with age, but the neural correlates are not well understood. In the present study, we used PA to investigate visuo-motor learning and error processing in older adults. Twenty older adults (56-85 yrs) and 20 younger adults (18-33 yrs) underwent a goal-oriented reaching task while wearing prism goggles as continuous EEG was recorded to examine neural correlates of error detection. We examined behavioural measures of PA, as well as ERP components previously found associated with the early and late phases of adaptation to visual distortion caused by the prism goggles. Our results indicate important age-related behavioural and neurophysiological differences. Older adults reached more slowly than younger adults but showed the same accuracy throughout the prism exposure. Older adults also displayed larger aftereffects, indicating preserved visuomotor adaptation. EEG results indicated similar initial error processing in older and younger adults, as measured by the feedback error related negativity (FRN). As seen previously in young adults, the P3a and P3b declined over the prism exposure phase in both groups. Older adults displayed reduced P3a amplitude compared to the younger group in the early phase of adaptation, however, suggesting reduced attentional orienting. Finally, the older group exhibited a greater P3b amplitude compared to the younger group in the later phases of adaptation, potentially a marker of enhanced context updating underlying spatial realignment, leading to their larger aftereffect. Implications for age-related learning differences and clinical applications are discussed.

Attentional impairment in Parkinson's disease is modulated by side of onset: Neurophysiological evidence

OBJECTIVE

Neurophysiological studies exploring involuntary attention have reported that electroencephalographic (EEG) measures can indicate impaired neural processing from initial stages of Parkinson's disease (PD). Since involuntary attention is regulated by right hemisphere networks and PD generally initiates its motor symptomatology unilaterally, whether involuntary attention is impaired depending on the onset side of PD remains unknown.

METHODS

We compared the neurophysiological correlates of involuntary attention among a PD group with left-side onset (L-PD), a PD group with right-side onset (R-PD) symptomatology, and a healthy control group (HC). All participants performed an auditory involuntary attention task while a digital EEG was recorded.

RESULTS

Our main finding was a reduction both in the P3a amplitude and evoked delta-theta phase alignment in the L-PD group compared to the HC. Further, there was a significant correlation between P3a amplitude and disease duration in the R-PD, but not in the L-PD group. Behaviorally, both clinical groups, and in particular L-PD, showed reduced orientation towards novel stimuli, and no reduction of distraction effects during the experiment.

CONCLUSIONS

Our results indicate that involuntary attention is differentially impaired in patients with left side onset of symptoms. Involuntary attention impairment might be present from initial stages of left onset PD and become progressively compromised in patients with right onset PD.

SIGNIFICANCE

The onset side of symptomatology should be considered for attentional impairment in PD.

Cortical oscillatory dysfunction in Parkinson disease during movement activation and inhibition

Response activation and inhibition are functions fundamental to executive control that are disrupted in Parkinson disease (PD). We used magnetoencephalography to examine event related changes in oscillatory power amplitude, peak latency and frequency in cortical networks subserving these functions and identified abnormalities associated with PD. Participants (N = 18 PD, 18 control) performed a cue/target task that required initiation of an un-cued movement (activation) or inhibition of a cued movement. Reaction times were variable but similar across groups. Task related responses in gamma, alpha, and beta power were found across cortical networks including motor cortex, supplementary and pre- supplementary motor cortex, posterior parietal cortex, prefrontal cortex and anterior cingulate. PD-related changes in power and latency were noted most frequently in the beta band, however, abnormal power and delayed peak latency in the alpha band in the pre-supplementary motor area was suggestive of a compensatory mechanism. PD peak power was delayed in pre-supplementary motor area, motor cortex, and medial frontal gyrus only for activation, which is consistent with deficits in un-cued (as opposed to cued) movement initiation characteristic of PD.

Neural Markers of Methylphenidate Response in Children With Attention Deficit Hyperactivity Disorder

Background

Despite widespread use of stimulants to treat ADHD, individual responses vary considerably and few predictors of response have been identified. The identification of reliable and clinically feasible biomarkers would facilitate a precision medicine approach to pharmacological treatment of ADHD. We test the hypothesis that two electroencephalography (EEG) based neural signatures of ADHD, resting aperiodic slope exponent and novelty P3 amplitude, are markers of methylphenidate response in children. We hypothesize that positive response to methylphenidate treatment will be associated with greater abnormality of both neural markers.

Methods

Twenty-nine 7-11 year-old children with ADHD and a history of methylphenidate treatment, and 30 controls completed resting EEG and visual oddball event related potential (ERP) paradigms. ADHD participants were characterized as methylphenidate responders (n = 16) or non-responders (n = 13) using the clinical global improvement (CGI-I) scale during blinded retrospective interview. All participants abstained from prescribed medications for at least 48 hours prior to the EEG.

Results

As expected, methylphenidate responders (CGI-I rating < 3) demonstrated attenuated P3 amplitude relative to controls. Unexpectedly, methylphenidate non-responders showed atypically flat aperiodic spectral slope relative to controls, while responders did not differ on this measure.

Conclusion

ADHD symptoms associated with atypical patterns of intrinsic neural activity may be less responsive to methylphenidate. In contrast, ADHD symptoms associated with abnormal frontal-striatal neural network excitation may be correctable with methylphenidate. Altogether, EEG is a feasible and promising candidate methodology for identifying biomarkers of stimulant response.

Assessment of event-related evoked potentials and China-Wechsler intelligence scale for cognitive dysfunction in children with obstructive sleep apnea

OBJECTIVE

To explore the relationship between obstructive sleep apnea (OSA) and cognitive impairment by combining event-related evoked potentials (ERPs) and China-Wechsler Younger Children Scale (C-WISC) in children with sleep-disordered breathing (SDB) with vs. without OSA.

METHODS

This was a retrospective case-control study of all consecutive children (n = 148) with adenoid tonsil hypertrophy between July 2017 and March 2019 at the Hospital.

RESULTS

The children were divided into the OSA (n = 102) and non-OSA (n = 46) groups. The apnea-hypopnea index (AHI), obstructive apnea index (OAI), and obstructive apnea-hypopnea index (OAHI) in the OSA group were elevated compared with those of the non-OSA group (all P < 0.001). The mean oxygen saturation (SaO₂) and SaO₂ nadir were lower in the OSA group compared with the non-OSA group (both P < 0.001). The respiratory arousal index (RAI) values in the OSA group were larger than those of the non-OSA group (P < 0.001). The P300 and N100 latencies in the OSA group were longer than those of the non-OSA group (both P < 0.001). Pearson's correlation analysis revealed correlations of the P300 peak latency with full-scale intelligence quotient (FIQ) (P < 0.001 and r = -0.527), verbal intelligence quotient (VIQ) (P < 0.001 and r = -0.448), and performance intelligence quotient (PIQ) (P < 0.001 and r = -0.515). There was a correlation between the N100 peak latency and PIQ (P = 0.026 and r = -0.183).

CONCLUSION

ERPs, as an objective measurement, might help assess cognitive impairment in children with OSA.

Parkinson's disease affects the neural alpha oscillations associated with speech-in-noise processing

Parkinson's disease (PD) has increasingly been associated with auditory dysfunction, including alterations regarding the control of auditory information processing. Although these alterations may interfere with the processing of speech in degraded listening conditions, behavioural studies have generally found preserved speech-in-noise recognition in PD. However, behavioural speech audiometry does not capture the neurophysiological mechanisms supporting speech-in-noise processing. Therefore, the aim of this study was to investigate the neural oscillatory mechanisms associated with speech-in-noise processing in PD. Twelve persons with PD and 12 age- and gender-matched healthy controls (HCs) were included in this study. Persons with PD were studied in the medication off condition. All subjects underwent an audiometric screening and performed a sentence-in-noise recognition task under simultaneous electroencephalography (EEG) recording. Behavioural speech recognition scores and self-reported ratings of effort, performance, and motivation were collected. Time-frequency analysis of EEG data revealed no significant difference between persons with PD and HCs regarding delta-theta (2-8 Hz) inter-trial phase coherence to noise and sentence onset. In contrast, significantly increased alpha (8-12 Hz) power was found in persons with PD compared with HCs during the sentence-in-noise recognition task. Behaviourally, persons with PD demonstrated significantly decreased speech recognition scores, whereas no significant differences were found regarding effort, performance, and motivation ratings. These results suggest that persons with PD allocate more cognitive resources to support speech-in-noise processing. The interpretation of this finding is discussed in the context of a top-down mediated compensation mechanism for inefficient filtering and degradation of auditory input in PD.

Evaluation of multi-feature auditory deviance detection in Parkinson's disease: a mismatch negativity study

Behavioral studies on auditory deviance detection in patients with Parkinson's disease (PD) have reported contradictory results. The primary aim of this study was to investigate auditory deviance detection of multiple auditory features in patients with PD by means of objective and reliable electroencephalographic (EEG) measurements. Twelve patients with early-stage PD and twelve age- and gender-matched healthy controls (HCs) were included in this study. Patients with PD participated without their regular dopaminergic medication. All subjects underwent an audiometric screening and performed a passive multi-feature mismatch negativity (MMN) paradigm. Repeated-measures analysis of variance (ANOVA) demonstrated no significant differences between patients with PD and HCs regarding MMN mean amplitude and latency for frequency, duration and gap deviants. Nevertheless, a trend towards increased MMN mean amplitude and latency was found in response to intensity deviants in patients with PD compared to HCs. Increased intensity MMN amplitude may indicate that more neural resources are allocated to the processing of intensity deviances in patients with PD compared to HCs. The interpretation of this intensity-specific MMN alteration is further discussed in the context of a compensatory mechanism for auditory intensity processing and involuntary attention switching in PD.

The Application of P300-Long-Latency Auditory-Evoked Potential in Parkinson Disease

Introduction Parkinson disease (PD) is a degenerative and progressive neurological disorder characterized by resting tremor, stiffness, bradykinesia, and postural instability. Despite the motor symptoms, PD patients also consistently show cognitive impairment or executive dysfunction. The auditory event-related potential P300 has been described as the best indicator of mental function, being highly dependent on cognitive skills, including attention and discrimination.

Objective To review the literature on the application and findings of P300 as an indicator of PD.

Data Analysis The samples ranged from 7 to 166 individuals. Young adult and elderly male patients composed most study samples. The Mini-Mental State Examination test, the Unified Parkinson Disease Rating Scale, and the Hoehn and Yahr Scale were used to assess neurological and cognitive function. In terms of testing hearing function, few studies have focused on parameters other than the P300. The factors we focused on were how the P300 was modified by cognitive effects, its correlation with different PD scales, the effect of performing dual tasks, the effect of fatigue, and the influence of drug treatments.

Conclusion The use of the P300 appears to be an effective assessment tool in patients with PD. This event-related potential seems to correlate well with other neurocognitive tests that measure key features of the disease.

Impairment of novelty-related theta oscillations and P3a in never medicated first-episode psychosis patients

We explored the neurophysiological activity underlying auditory novelty detection in antipsychotic-naive patients with a first episode of psychosis (FEP). Fifteen patients with a non-affective FEP and 13 healthy controls underwent an active involuntary attention task along with an EEG acquisition. Time-frequency representations of power, phase locking, and fronto-parietal connectivity were calculated. The P3a event-related potential was extracted as well. Compared to controls, the FEP group showed reduced theta phase-locking and fronto-parietal connectivity evoked by deviant stimuli. Also, the P3a amplitude was significantly reduced. Moreover, reduced theta connectivity was associated with more severe negative symptoms within the FEP group. Reduced activity (phase-locking and connectivity) of novelty-related theta oscillations, along with P3a reduction, may represent a failure to synchronize large-scale neural populations closely related to fronto-parietal attentional networks, and might be explored as a potential biomarker of disease severity in patients with emerging psychosis, given its association with negative symptoms.

Characterization of EEG Data Revealing Relationships With Cognitive and Motor Symptoms in Parkinson's Disease: A Systematic Review

Recent research regards the electroencephalogram (EEG) as a promising method to study real-time brain dynamic changes in patients with Parkinson's disease (PD), but a deeper understanding is needed to discern coincident pathophysiology, patterns of changes, and diagnosis. This review summarized recent research on EEG characterization related to the cognitive and motor functions in PD patients and discussed its potential to be used as diagnostic biomarkers. Thirty papers out of 220 published from 2010 to 2020 were reviewed. Movement abnormalities and cognitive decline are related to changes in EEG spectrum and event-related potentials (ERPs) during typical oddball paradigms and/or combined motor tasks. Abnormalities in β and δ frequency bands are, respectively the main manifestation of dyskinesia and cognitive decline in PD. The review showed that PD patients have noteworthy changes in specific EEG characterizations, however, the underlying mechanism of the interrelation between gait and cognitive is still unclear. Understanding the specific nature of the relationship is essential for development of novel invasive clinical diagnostic and therapeutic methods.

Dopaminergic modulation of novelty repetition in Parkinson's disease: A study of P3 event-related brain potentials

OBJECTIVE

Parkinson's Disease (PD) is a neurodegenerative disease caused by the loss of dopaminergic neurons. Cognitive impairments have been reported using the event-related potential (ERP) technique. Patients show reduced novelty P3 (nP3) amplitudes in oddball experiments, a response to infrequent, surprising stimuli, linked to the orienting response of the brain. The nP3 is thought to depend on dopaminergic neuronal pathways though the effect of dopaminergic medication in PD has not yet been investigated.

METHODS

Twenty-two patients with PD were examined "on" and "off" their regular dopaminergic medication in a novelty 3-stimulus-oddball task. Thirty-four healthy controls were also examined over two sessions, but received no medication. P3 amplitudes were compared throughout experimental conditions.

RESULTS

All participants showed sizeable novelty difference ERP effects, i.e. n_dP3 amplitudes, during both testing sessions. An interaction of diagnosis, medication and testing order was also found, indicating that dopaminergic medication modulated n_dP3 in patients with PD across the two testing sessions: We observed enhanced n_dP3 amplitudes from PD patients who were off medication on the second testing session.

CONCLUSION

Patients with PD 'off' medication showed ERP evidence for repetition-related enhancement of novelty responses. Dopamine depletion in neuronal pathways that are affected by mid-stage PD possibly accounts for this modulation of novelty processing.

SIGNIFICANCE

The data in this study potentially suggest that repetition effects on novelty processing in patients with PD are enhanced by dopaminergic depletion.

Changes in the EEG spectral power during dual-task walking with aging and Parkinson's disease: initial findings using Event-Related Spectral Perturbation analysis

BACKGROUND

The ability to maintain adequate motor-cognitive performance under increasing task demands depends on the regulation and coordination of neural resources. Studies have shown that such resources diminish with aging and disease. EEG spectral analysis is a method that has the potential to provide insight into neural alterations affecting motor-cognitive performance. The aim of this study was to assess changes in spectral analysis during dual-task walking in aging and disease METHODS: 10 young adults, ten older adults, and ten patients with Parkinson's disease (PD) completed an auditory oddball task while standing and while walking on a treadmill. Spectral power within four frequency bandwidths, delta (< 4 Hz), theta (4-8 Hz), alpha (8-12 Hz), and beta (12-30 Hz), was calculated using Event-Related Spectral Perturbation (ERSP) analyses and compared between single task and dual task and between groups.

RESULTS

Differences in ERSP were found in all groups between the single and dual-task conditions. In response to dual-task walking, beta increased in all groups (p < 0.026), delta decreased in young adults (p = 0.03) and patients with PD (0.015) while theta increased in young adults (p = 0.028) but decreased in older adults (p = 0.02) and patients with PD (p = 0.015). Differences were seen between the young, the older adults, and the patients with PD.

CONCLUSIONS

These findings are the first to show changes in the power of different frequency bands during dual-task walking with aging and disease. These specific brain modulations may reflect deficits in readiness and allocation of attention that may be responsible for the deficits in dual-task performance.

Future Perspectives on the Relevance of Auditory Markers in Prodromal Parkinson's Disease

Research on auditory processing in Parkinson's disease (PD) has recently made substantial progress. At present, evidence has been found for altered auditory processing in the clinical stage of PD. The auditory alterations in PD have been demonstrated with low-cost and non-invasive assessments that are already used in routine clinical practice. Since auditory alterations have been reported early in disease progression, it would be highly relevant to investigate whether auditory markers could be provided in the prodromal stage of PD. In addition, auditory alterations in early stage PD might be modulated by dopaminergic medication. Therefore, the aim of this review is (1) to summarize the literature on auditory processing in PD with a specific focus on the early disease stages, (2) to give future perspectives on which audiological and electrophysiological measurements could be useful in the prodromal stage of PD and (3) to assess the effect of dopaminergic medication on potential auditory markers in the prodromal stage of PD.

Deficits in monitoring self-produced speech in Parkinson's disease

OBJECTIVE

Speech deficits are common in Parkinson's disease, and behavioural findings suggest that the deficits may be due to impaired monitoring of self-produced speech. The neural mechanisms of speech deficits are not well understood. We examined a well-documented electrophysiological correlate of speech self-monitoring in patients with Parkinson's disease and control participants.

METHODS

We measured evoked electroencephalographic responses to self-produced and passively heard sounds (/a/ phonemes) in age-matched controls (N = 18), and Parkinson's disease patients who had minor speech impairment, but reported subjectively experiencing no speech deficits (N = 17).

RESULTS

During speaking, auditory evoked activity 100 ms after phonation (N1 wave) was less suppressed in Parkinson's disease than controls when compared to the activity evoked by passively heard phonemes. This difference between the groups was driven by increased amplitudes to self-produced phonemes, and reduced amplitudes passively heard phonemes in Parkinson's disease.

CONCLUSIONS

The finding indicates that auditory evoked activity is abnormally modulated during speech in Parkinson's patients who do not subjectively notice speech impairment. This mechanism could play a role in producing speech deficits in as the disease progresses.

SIGNIFICANCE

Our study is the first to show abnormal early auditory electrophysiological correlates of monitoring speech in Parkinson's disease patients.

Central auditory processing in parkinsonian disorders: A systematic review

Altered auditory processing has been increasingly recognized as a non-motor feature in parkinsonian disorders. This systematic review provides an overview of behavioral and electrophysiological literature on central auditory processing in patients with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). A systematic database search was conducted and yielded 88 studies that met the intelligibility criteria. The collected data revealed distinct impairments in a range of central auditory processes in PD, including altered deviance detection of basic auditory features, auditory brainstem processing, auditory gating and selective auditory attention. In contrast to PD, literature on central auditory processing in atypical parkinsonian disorders was relatively scarce, but provided some evidence for impaired central auditory processing in MSA and PSP. The interpretation of these findings is discussed and suggestions for further research are offered.

Auditory Dysfunction in Parkinson's Disease

PD is a progressive and complex neurological disorder with heterogeneous symptomatology. PD is characterized by classical motor features of parkinsonism and nonmotor symptoms and involves extensive regions of the nervous system, various neurotransmitters, and protein aggregates. Extensive evidence supports auditory dysfunction as an additional nonmotor feature of PD. Studies indicate a broad range of auditory impairments in PD, from the peripheral hearing system to the auditory brainstem and cortical areas. For instance, research demonstrates a higher occurrence of hearing loss in early-onset PD and evidence of abnormal auditory evoked potentials, event-related potentials, and habituation to novel stimuli. Electrophysiological data, such as auditory P3a, also is suggested as a sensitive measure of illness duration and severity. Improvement in auditory responses following dopaminergic therapies also indicates the presence of similar neurotransmitters (i.e., glutamate and dopamine) in the auditory system and basal ganglia. Nonetheless, hearing impairments in PD have received little attention in clinical practice so far. This review summarizes evidence of peripheral and central auditory impairments in PD and provides conclusions and directions for future empirical and clinical research. © 2020 International Parkinson and Movement Disorder Society.

Auditory mismatch detection, distraction, and attentional reorientation (MMN-P3a-RON) in neurological and psychiatric disorders: A review

Involuntary attention allows for the detection and processing of novel and potentially relevant stimuli that lie outside of cognitive focus. These processes comprise change detection in sensory contexts, automatic orientation toward this change, and the selection of adaptive responses, including reorientation to the original goal in cases when the detected change is not relevant for task demands. These processes have been studied using the Event-Related Potential (ERP) technique and have been associated to the Mismatch Negativity (MMN), the P3a, and the Reorienting Negativity (RON) electrophysiological components, respectively. This has allowed for the objective evaluation of the impact of different neuropsychiatric pathologies on involuntary attention. Additionally, these ERP have been proposed as alternative measures for the early detection of disease and the tracking of its progression. The objective of this review was to integrate the results reported to date about MMN, P3a, and RON in different neurological and psychiatric disorders. We included experimental studies with clinical populations that reported at least two of these three components in the same experimental paradigm. Overall, involuntary attention seems to reflect the state of cognitive integrity in different pathologies in adults. However, if the main goal for these ERP is to consider them as biomarkers, more research about their pathophysiological specificity in each disorder is needed, as well as improvement in the general experimental conditions under which these components are elicited. Nevertheless, these ERP represent a valuable neurophysiological tool for early detection and follow-up of diverse clinical populations.

ERPs predict symptomatic distress and recovery in sub-acute mild traumatic brain injury

Mild traumatic brain injury (mTBI) can affect high-level executive functioning long after somatic symptoms resolve. We tested if simple EEG responses within an oddball paradigm could capture variance relevant to this clinical problem. The P3a and P3b components reflect bottom-up and top-down processes driving engagement with exogenous stimuli. Since these features are related to primitive decision abilities, abnormal amplitudes following mTBI may account for problems in the ability to exert executive control. Sub-acute (<2 weeks) mTBI participants (N = 38) and healthy controls (N = 24) were assessed at an initial session as well as a two-month follow-up (sessions 1 and 2). We contrasted the initial assessment to a comparison group of participants with chronic symptomatology following brain injury (N = 23). There were no group differences in P3a or P3b amplitudes. Yet in the sub-acute mTBI group, higher symptomatology on the Frontal Systems Behavior scale (FrSBe), a questionnaire validated as measuring symptomatic distress related to frontal lobe injury, correlated with lower P3a in session 1. This relationship was replicated in session 2. These findings were distinct from chronic TBI participants, who instead expressed a relationship between increased FrSBe symptoms and a lower P3b component. In the sub-acute group, P3b amplitudes in the first session correlated with the degree of symptom change between sessions 1 and 2, above and beyond demographic predictors. Controls did not show any relationship between FrSBe symptoms and P3a or P3b. These findings identify symptom-specific alterations in neural systems that vary along the time course of post-concussive symptomatology.

Insights into cognitive decline in spinocerebellar Ataxia type 2: a P300 event-related brain potential study

BACKGROUND

Cognitive decline is a common non-motor feature characterizing Spinocerebellar Ataxia type 2 (SCA2) during the prodromal stage, nevertheless a reduced number of surrogate biomarkers of these alterations have been described.

OBJECTIVE

To provide insights into cognitive dysfunction in SCA2 patients using P300 event-related potentials (ERP) and to evaluate these measures as biomarkers of the disease.

METHODS

A cross-sectional study was performed with 30 SCA2 patients, 20 preclinical carriers and 33 healthy controls, who underwent visual, auditory P300 ERPs, and neurological examinations and ataxia scoring.

RESULTS

SCA2 patients showed significant increase in P300 latencies and decrease of P300 amplitudes for visual and auditory stimuli, whereas preclinical carriers exhibit a less severe, but significant prolongation of P300 latencies. Multiple regression analyses disclosed a significant effect of SARA score on visual P300 abnormalities in patients as well as of the time to ataxia onset on visual P300 latencies in preclinical carriers.

CONCLUSIONS

This paper demonstrated the role of P300 ERP for the study of attentional, discriminative and working memory abnormalities in SCA2 patients and for the search of surrogate biomarkers from prodromal to the symptomatic stages. Moreover, our findings provide psychophysiological evidences supporting the cerebellar involvement in cognitive processes and allows us to identify promising outcome measures for future trials focusing on cognitive dysfunction.

Action Observation in People with Parkinson's Disease. A Motor⁻Cognitive Combined Approach for Motor Rehabilitation. A Preliminary Report

The aim of this study was to assess the role of Action Observation (AO) to improve balance, gait, reduce falls, and to investigate the changes in P300 pattern. Five cognitively intact People with Parkinson’s disease (PwP) were enrolled in this prospective, quasi-experimental study to undergo a rehabilitation program of AO for gait and balance recovery of 60 min, three times a week for four weeks. The statistical analysis showed significant improvements for Unified Parkinson’s Disease Rating Scale (UPDRS) motor section III p = 0.0082, Short form 12-items Healthy Survey (SF-12) Mental Composite Score (MCS) p = 0.0007, Freezing of gait Questionnaire (FOG-Q) p = 0.0030, The 39-items Parkinson’s Disease Questionnaire (PDQ-39) p = 0.100, and for P300ld p = 0.0077. In conclusion, AO reveals to be a safe and feasible paradigm of rehabilitative exercise in cognitively preserved PwP.

Effects of Transcutaneous Vagus Nerve Stimulation (tVNS) on the P300 and Alpha-Amylase Level: A Pilot Study

Recent research suggests that the P3b may be closely related to the activation of the locus coeruleus-norepinephrine (LC-NE) system. To further study the potential association, we applied a novel technique, the non-invasive transcutaneous vagus nerve stimulation (tVNS), which is speculated to increase noradrenaline levels. Using a within-subject cross-over design, 20 healthy participants received continuous tVNS and sham stimulation on two consecutive days (stimulation counterbalanced across participants) while performing a visual oddball task. During stimulation, oval non-targets (standard), normal-head (easy) and rotated-head (difficult) targets, as well as novel stimuli (scenes) were presented. As an indirect marker of noradrenergic activation we also collected salivary alpha-amylase (sAA) before and after stimulation. Results showed larger P3b amplitudes for target, relative to standard stimuli, irrespective of stimulation condition. Exploratory post hoc analyses, however, revealed that, in comparison to standard stimuli, easy (but not difficult) targets produced larger P3b (but not P3a) amplitudes during active tVNS, compared to sham stimulation. For sAA levels, although main analyses did not show differential effects of stimulation, direct testing revealed that tVNS (but not sham stimulation) increased sAA levels after stimulation. Additionally, larger differences between tVNS and sham stimulation in P3b magnitudes for easy targets were associated with larger increase in sAA levels after tVNS, but not after sham stimulation. Despite preliminary evidence for a modulatory influence of tVNS on the P3b, which may be partly mediated by activation of the noradrenergic system, additional research in this field is clearly warranted. Future studies need to clarify whether tVNS also facilitates other processes, such as learning and memory, and whether tVNS can be used as therapeutic tool.

Mid-frontal theta activity is diminished during cognitive control in Parkinson's disease

Mid-frontal theta activity underlies cognitive control. These 4-8 Hz rhythms are modulated by cortical dopamine and can be abnormal in patients with Parkinson's disease (PD). Here, we investigated mid-frontal theta deficits in PD patients during a task explicitly involving cognitive control. We collected scalp EEG from high-performing PD patients and demographically matched controls during performance of a modified Simon reaction-time task. This task involves cognitive control to adjudicate response conflict and error-related adjustments. Task performance of PD patients was indistinguishable from controls, but PD patients had less mid-frontal theta modulations around cues and responses. Critically, PD patients had attenuated mid-frontal theta activity specifically associated with response conflict and post-error processing. These signals were unaffected by medication or motor scores. Post-error mid-frontal theta activity was correlated with disease duration. Classification of control vs. PD from these data resulted in a specificity of 69% and a sensitivity of 72%. These findings help define the scope of mid-frontal theta aberrations during cognitive control in PD, and may provide insight into the nature of PD-related cognitive dysfunction.

Top-Down Control of Alpha Phase Adjustment in Anticipation of Temporally Predictable Visual Stimuli

Alpha oscillations (8-14 Hz) are proposed to represent an active mechanism of functional inhibition of neuronal processing. Specifically, alpha oscillations are associated with pulses of inhibition repeating every ∼100 msec. Whether alpha phase, similar to alpha power, is under top-down control remains unclear. Moreover, the sources of such putative top-down phase control are unknown. We designed a cross-modal (visual/auditory) attention study in which we used magnetoencephalography to record the brain activity from 34 healthy participants. In each trial, a somatosensory cue indicated whether to attend to either the visual or auditory domain. The timing of the stimulus onset was predictable across trials. We found that, when visual information was attended, anticipatory alpha power was reduced in visual areas, whereas the phase adjusted just before the stimulus onset. Performance in each modality was predicted by the phase of the alpha oscillations previous to stimulus onset. Alpha oscillations in the left pFC appeared to lead the adjustment of alpha phase in visual areas. Finally, alpha phase modulated stimulus-induced gamma activity. Our results confirm that alpha phase can be top-down adjusted in anticipation of predictable stimuli and improve performance. Phase adjustment of the alpha rhythm might serve as a neurophysiological resource for optimizing visual processing when temporal predictions are possible and there is considerable competition between target and distracting stimuli.

Brain oscillations reveal impaired novelty detection from early stages of Parkinson's disease

The identification of reliable biomarkers for early diagnosis and progression tracking of neurodegenerative diseases has become an important objective in clinical neuroscience in the last years. The P3a event-related potential, considered as the neurophysiological hallmark of novelty detection, has been shown to be reduced in Parkinson's disease (PD) and proposed as a sensitive measure for illness duration and severity. Our aim for this study was to explore for the first time whether impaired novelty detection could be observed through phase- and time-locked brain oscillatory activity at early PD. Twenty-seven patients with idiopathic PD at early stages (disease duration <5 years and Hoehn and Yahr stage <3) were included. A healthy control group (n = 24) was included as well. All participants performed an auditory involuntary attention task including frequent and deviant tones while a digital EEG was obtained. A neuropsychological battery was administered as well. Time-frequency representations of power and phase-locked oscillations and P3a amplitudes were compared between groups. We found a significant reduction of power and phase locking of slow oscillations (3-7 Hz) for deviant tones in the PD group compared to controls in the P3a time range (300-550 ms). Also, reduced modulation of late induced (not phase locked) alpha-beta oscillations (400-650 ms, 8-25 Hz) was observed in the PD group after deviant tones onset. The P3a amplitude was predicted by years of evolution in the PD group. Finally, while phase-locked slow oscillations were associated with task behavioral distraction effects, induced alpha-beta activity was related to cognitive flexibility performance. Our results show that novelty detection impairment can be identified in neurophysiological terms from very early stages of PD, and such impairment increases linearly as the disease progresses. Also, induced alpha-beta oscillations underlying novelty detection are related to executive functioning.

P300 Wave Changes in Patients with Parkinson's Disease

Introduction:

Parkinson’s disease (PD) is chronic progressive neurodegenerative disease. In patients with Parkinson’s disease among other symptoms occur cognitive dysfunctions, which can be shown by P300 wave changes.

Aim:

The aim of this study was to demonstrate that patients with Parkinson’s disease have reduced amplitude and prolonged latency, longer than 300 ± 10 ms.

Material and Methods:

The study included 21 patient suffering from Parkinson’s disease. After reviewing the medical records and analyzes the inclusion and exclusion criteria, patients were subjected to the same procedure examining auditory cognitive potentials (P300 wave) and the results were analyzed and compared to reference value for healthy population.

Results:

We have shown that patients with Parkinson’s disease have prolonged P300 targeted and frequent stimulus latency compared to reference value for healthy population. From 21 patient 18 had a pathological P300 target stimulus amplitude, and even 20 patients had pathological P300 frequent stimulus amplitude.

Conclusion:

People with Parkinson’s disease have altered P300 which indicates the presence of cognitive dysfunction in these patients.

Cognitive Impairment in Parkinson's Disease Is Reflected with Gradual Decrease of EEG Delta Responses during Auditory Discrimination

Parkinson’s disease (PD) is a neurodegenerative disease that is characterized by loss of dopaminergic neurons in the substantia nigra. Mild Cognitive impairment (MCI) and dementia may come along with the disease. New indicators are necessary for detecting patients that are likely to develop dementia. Electroencephalogram (EEG) Delta responses are one of the essential electrophysiological indicators that could show the cognitive decline. Many research in literature showed an increase of delta responses with the increased cognitive load. Furthermore, delta responses were decreased in MCI and Alzheimer disease in comparison to healthy controls during cognitive paradigms. There was no previous study that analyzed the delta responses in PD patients with cognitive deficits. The present study aims to fulfill this important gap. 32 patients with Parkinson’s disease (12 of them were without any cognitive deficits, 10 of them were PD with MCI, and 10 of them were PD with dementia) and 16 healthy subjects were included in the study. Auditory simple stimuli and Auditory Oddball Paradigms were applied. The maximum amplitudes of each subject’s delta response (0.5–3.5 Hz) in 0–600 ms were measured for each electrode and for each stimulation. There was a significant stimulation × group effect [F_{(df = 6,88)} = 3,21; p < 0.015; ηp2 = 0.180], which showed that the difference between groups was specific to the stimulation. Patients with Parkinson’s disease (including PD without cognitive deficit, PD with MCI, and PD with dementia) had reduced delta responses than healthy controls upon presentation of target stimulation (p < 0.05, for all comparisons). On the other hand, this was not the case for non-target and simple auditory stimulation. Furthermore, delta responses gradually decrease according to the cognitive impairment in patients with PD.

Conclusion: The results of the present study showed that cognitive decline in PD could be represented with decreased event related delta responses during cognitive stimulations. Furthermore, the present study once more strengthens the hypothesis that decrease of delta oscillatory responses could be the candidate of a general electrophysiological indicator for cognitive impairment.

Diminished EEG habituation to novel events effectively classifies Parkinson's patients

OBJECTIVES

We aimed to test if EEG responses to novel events reliably dissociated individuals with Parkinson's disease and controls, and if this dissociation was sensitive and specific enough to be a candidate biomarker of cognitive dysfunction in Parkinson's disease.

METHODS

Participants included N = 25 individuals with Parkinson's disease and an equal number of well-matched controls. EEG was recorded during a three-stimulus auditory oddball paradigm both ON and OFF medication.

RESULTS

While control participants showed reliable EEG habituation to novel events over time, individuals with Parkinson's did not. In the OFF condition, individual differences in habituation correlated with years since diagnosis. Pattern classifiers achieved high sensitivity and specificity in discriminating patients from controls, with a maximum accuracy of 82%. Most importantly, the confidence of the classifier was related to years since diagnosis, and this correlation increased as the time course of differential habituation increasingly distinguished the groups.

CONCLUSIONS

These findings identify systemic alteration in an obligatory neural mechanism that may contribute to higher-level cognitive dysfunction in Parkinson's disease.

SIGNIFICANCE

These findings suggest that EEG responses to novel events in this rapid, simple, and inexpensive test have tremendous promise for tracking individual trajectories of cognitive dysfunction in Parkinson's disease.

The Patient Repository for EEG Data + Computational Tools (PRED+CT)

Electroencephalographic (EEG) recordings are thought to reflect the network-wide operations of canonical neural computations, making them a uniquely insightful measure of brain function. As evidence of these virtues, numerous candidate biomarkers of different psychiatric and neurological diseases have been advanced. Presumably, we would only need to apply powerful machine-learning methods to validate these ideas and provide novel clinical tools. Yet, the reality of this advancement is more complex: the scale of data required for robust and reliable identification of a clinical biomarker transcends the ability of any single laboratory. To surmount this logistical hurdle, collective action and transparent methods are required. Here we introduce the Patient Repository of EEG Data + Computational Tools (PRED+CT: predictsite.com). The ultimate goal of this project is to host a multitude of available tasks, patient datasets, and analytic tools, facilitating large-scale data mining. We hope that successful completion of this aim will lead to the development of novel EEG biomarkers for differentiating populations of neurological and psychiatric disorders.

Cognitive flexibility in neurological disorders: Cognitive components and event-related potentials

Performance deficits on the Wisconsin Card Sorting Test (WCST) in patients with prefrontal cortex (PFC) lesions are traditionally interpreted as evidence for a role of the PFC in cognitive flexibility. However, WCST deficits do not occur exclusively after PFC lesions, but also in various neurological and psychiatric disorders. We propose a multi-component approach that can accommodate this pattern of omnipresent WCST deficits: the WCST is not a pure test of cognitive flexibility, but relies on the effective functioning of multiple dissociable cognitive components. Our review of recent efforts to decompose WCST performance deficits supports this view by revealing that WCST deficits in different neurological disorders can be attributed to alterations in different components. Frontoparietal changes underlying impaired set shifting seem to give rise to WCST deficits in patients with amyotrophic lateral sclerosis, whereas the WCST deficits associated with primary dystonia and Parkinson's disease are rather related to frontostriatal changes underlying deficient rule inference. Clinical implications of these findings and of a multi-component view of WCST performance are discussed.

Olfactory impairment in Parkinson's disease is a consequence of central nervous system decline

Early diagnosis and timely treatment of Parkinson's disease are essential factors to provide these patients with a longer period of a better quality of life. Olfactory loss is among the first non-motor symptoms of the disease; however, in light of the many causes of smell loss, it is a very unspecific biomarker and should only be used as part of a diagnostic test battery. In this study, we investigated the olfactory response in 71 subjects, consisting of Parkinson's disease patients, hyposmic and anosmic patients of other causes, and normosmic individuals searching for sensitive, distinct biomarkers for which we used scalp event-related 64-channel electroencephalography and psychophysical tests. The analysis of the global field power indicated significant measurable differences between patients with Parkinson's disease and otherwise olfactory dysfunctional and normosmic individuals. The localization of brain sources, in particular, provides evidence for differences in mainly late EEG-components suggesting a decline of central brain networks as a causal factor for olfactory loss in Parkinson's disease. The findings indicate a different pattern of olfactory processing in patients with Parkinson's disease compared to olfactory dysfunctions of other origin, which provide further insights into the mechanisms behind olfactory dysfunction in Parkinson's.

Dopaminergic modulation of performance monitoring in Parkinson's disease: An event-related potential study

Monitoring one’s actions is essential for goal-directed performance. In the event-related potential (ERP), errors are followed by fronto-centrally distributed negativities. These error(-related) negativity (N_e/ERN) amplitudes are often found to be attenuated in patients with Parkinson’s disease (PD) compared to healthy controls (HC). Although N_e/ERN has been proposed to be related to dopaminergic neuronal activity, previous research did not find evidence for effects of dopaminergic medication on N_e/ERN amplitudes in PD. We examined 13 PD patients “on” and “off” dopaminergic medication. Their response-locked ERP amplitudes (obtained on correct [N_c/CRN] and error [N_e/ERN] trials of a flanker task) were compared to those of 13 HC who were tested twice as well, without receiving dopaminergic medication. While PD patients committed more errors than HC, error rates were not significantly modulated by dopaminergic medication. PD patients showed reduced N_e/ERN amplitudes relative to HC; however, this attenuation of response-locked ERP amplitudes was not specific to errors in this study. PD-related attenuation of response-locked ERP amplitudes was most pronounced when PD patients were on medication. These results suggest overdosing of dopaminergic pathways that are relatively spared in PD, but that are related to the generation of the N_e/ERN, notably pathways targeted on the medial prefrontal cortex.

Shifting of attentional set is inadequate in severe burnout: Evidence from an event-related potential study

Individuals with prolonged occupational stress often report difficulties in concentration. Work tasks often require the ability to switch back and forth between different contexts. Here, we studied the association between job burnout and task switching by recording event-related potentials (ERPs) time-locked to stimulus onset during a task with simultaneous cue-target presentation and unpredictable switches in the task. Participants were currently working people with severe, mild, or no burnout symptoms. In all groups, task performance was substantially slower immediately after task switch than during task repetition. However, the error rates were higher in the severe burnout group than in the mild burnout and control groups. Electrophysiological data revealed an increased parietal P3 response for the switch trials relative to repetition trials. Notably, the response was smaller in amplitude in the severe burnout group than in the other groups. The results suggest that severe burnout is associated with inadequate processing when rapid shifting of attention between tasks is required resulting in less accurate performance.

Attention in Parkinson's disease with fatigue: evidence from the attention network test

Fatigue is a non-specific symptom that is common in chronic diseases and represents one of the most disabling symptoms in Parkinson's disease. PD patients often experience cognitive deficits related above all to executive functions. The relationship between cognitive changes and fatigue in PD patients has not been explored in depth. The Attention Network Test (ANT) is a rapid, widely used test to measure the efficiency of three attentional networks, i.e., alerting, orienting, and executive, by evaluating reaction times (RTs) in response to visual stimuli. To assess the association between fatigue and the efficiency of the attentional networks, according to the Posnerian view, ANT was administered to 15 parkinsonian patients with fatigue (PFS-16 > 2.95), 17 parkinsonian patients without fatigue, and 37 age- and sex-matched healthy controls. Anxiety, depression, quality of sleep, and quality of life were also assessed. Parkinsonian patients displayed significantly longer RTs and lower executive network efficiency than controls. Patients with fatigue displayed significantly lower executive network efficiency than patients without fatigue. Moreover, patients with fatigue exhibited a lower accuracy than either patients without fatigue or controls. Finally, patients without fatigue displayed a more efficient alerting network than either patients with fatigue or controls. Although the pathogenesis of fatigue is multifactorial, our results indicate that fatigue may be closely related to an alteration of the striato-thalamo-cortical loop connecting the neostriatum to the prefrontal cortex, which is also responsible for the executive dysfunction that is typical of Parkinson's disease.

Can an auditory multi-feature optimal paradigm be used for the study of processes associated with attention capture in passive listeners?

OBJECTIVE

A rarely occurring and highly relevant auditory stimulus occurring outside of the current focus of attention can cause a switching of attention. Such attention capture is often studied in oddball paradigms consisting of a frequently occurring "standard" stimulus which is changed at odd times to form a "deviant". The deviant may result in the capturing of attention. An auditory ERP, the P3a, is often associated with this process. To collect a sufficient amount of data is however very time-consuming. A more multi-feature "optimal" paradigm has been proposed but it is not known if it is appropriate for the study of attention capture.

METHODS

An optimal paradigm was run in which 6 different rare deviants (p=.08) were separated by a standard stimulus (p=.50) and compared to results when 4 oddball paradigms were also run.

RESULTS

A large P3a was elicited by some of the deviants in the optimal paradigm but not by others. However, very similar results were observed when separate oddball paradigms were run.

CONCLUSIONS & SIGNIFICANCE

The present study indicates that the optimal paradigm provides a very time-saving method to study attention capture and the P3a.

Apathy, Novelty Processing, and the P3 Potential in Parkinson's Disease

Parkinson's disease (PD) is characterized by deficits in goal-directed behavior as well as mood and motivational symptoms, including apathy, depression, and anxiety. The present study investigated novelty processing in PD, using event-related potentials (ERPs) to characterize electrophysiological reflections of visual novelty processing. Since apathy has been associated with decreased novelty processing (P3 potentials) in highly apathetic PD patients, we were particularly interested to see if this relationship exists in a sample of PD patients with heterogeneous levels of apathy. Non-demented patients with PD receiving dopaminergic treatment (n = 14) and healthy control participants (n = 12) completed a three-stimulus oddball task while EEG was recorded. Relative to controls, the PD patients exhibited reductions in centrofrontally distributed P3 potentials when viewing novel distracters during this task. Distracter-related P3 amplitudes evoked by novel distracters were strongly associated with apathy symptoms, even after controlling for the effects of depression, anxiety, and executive function. Executive dysfunction was also predictive of novelty-related P3 processing, yet this relationship was independent from that of apathy. These findings suggest that the brain's electrophysiological response to novelty is closely related to both motivational and cognitive symptoms in PD, even for patients whose apathy symptoms are not excessive. These results have significant implications for our understanding of non-motor symptoms in this clinical population.

Meta-analytical and electrophysiological evidence for executive dysfunction in primary dystonia

Impaired motor control in primary dystonia has been linked to cortico-basal ganglia alterations that may also give rise to changes in executive functioning. However, no conclusive evidence for executive dysfunction in patients with primary dystonia has been reported yet. We conducted a meta-analysis of the relationship between primary dystonia and performance on the Wisconsin Card Sorting Test (WCST), an established test of executive functioning. Its results revealed a significant effect of medium size, indicating that primary dystonia is associated with moderate performance deficits on the WCST. Building on this finding, we conducted an event-related potential (ERP) study to elucidate the cognitive and neural mechanisms underlying executive dysfunction in primary dystonia. Eighteen patients with blepharospasm, a common form of primary focal dystonia, and 34 healthy matched controls completed a computerized version of the WCST. We specifically compared indicators of two distinct components of executive functioning: set shifting and rule inference. On a behavioral level, blepharospasm patients seemed to have particular difficulty integrating information to infer the correct task rule. In addition, P3a amplitude (as an electrophysiological marker of rule-inference processes) was selectively attenuated in blepharospasm patients. Executive dysfunction in blepharospasm can thus rather be attributed to a rule-inference deficit, whereas set-shifting abilities appear to be relatively unaffected by the disease. Moreover, P3a amplitude attenuation was related to disease duration, indicating that this ERP might serve as a neural indicator of disease progression and executive dysfunction in primary dystonia. These results demonstrate for the first time that pathophysiological alterations in primary dystonia might affect cortical activation for executive functioning.