Dysfunctions of automatic (P300a) and controlled (P300b) processing in Parkinson's disease

Current trends and opportunities in the methodology of electrodermal activity measurement

Electrodermal activity (EDA) has been measured in the laboratory since the late 1800s. Although the influence of sudomotor nerve activity and the sympathetic nervous system on EDA is well established, the mechanisms underlying EDA signal generation are not completely understood. Owing to simplicity of instrumentation and modern electronics, these measurements have recently seen a transfer from the laboratory to wearable devices, sparking numerous novel applications while bringing along both challenges and new opportunities. In addition to developments in electronics and miniaturization, current trends in material technology and manufacturing have sparked innovations in electrode technologies, and trends in data science such as machine learning and sensor fusion are expanding the ways that measurement data can be processed and utilized. Although challenges remain for the quality of wearable EDA measurement, ongoing research and developments may shorten the quality gap between wearable EDA and standardized recordings in the laboratory. In this topical review, we provide an overview of the basics of EDA measurement, discuss the challenges and opportunities of wearable EDA, and review recent developments in instrumentation, material technology, signal processing, modeling and data science tools that may advance the field of EDA research and applications over the coming years.

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.

Longitudinal associations between mismatch negativity and disability in early schizophrenia- and affective-spectrum disorders

BACKGROUND

Impaired mismatch negativity (MMN) is a robust finding in schizophrenia and, more recently, similar impairments have been reported in other psychotic- and affective-disorders (including at early stages of illness). Although cross-sectional studies have been numerous, there are few longitudinal studies that have explored the predictive value of this event-related potential in relation to clinical/functional outcomes. This study assessed changes in MMN (and the concomitant P3a) amplitude over time and aimed to determine the longitudinal relationship between MMN/P3a and functional outcomes in patients recruited during the early stage of a schizophrenia- or affective-spectrum disorder.

METHODS

Sixty young patients with schizophrenia- and affective-spectrum disorders and 30 healthy controls underwent clinical, neuropsychological and neurophysiological assessment at baseline. Thirty-one patients returned for clinical and neuropsychological follow-up 12-30months later, with 28 of these patients also repeating neurophysiological assessment. On both occasions, MMN/P3a was elicited using a two-tone passive auditory paradigm with duration deviants.

RESULTS

Compared with controls, patients showed significantly impaired temporal MMN amplitudes and trend-level deficits in central MMN/P3a amplitudes at baseline. There were no significant differences for MMN measures between the diagnostic groups, whilst the schizophrenia-spectrum group showed reduced P3a amplitudes compared to those with affective-spectrum disorders. For those patients who returned for follow-up, reduced temporal MMN amplitude at baseline was significantly associated with greater levels of occupational disability, and showed trend-level associations with general and social disability at follow-up. Paired t-tests revealed that MMN amplitudes recorded at the central-midline site were significantly reduced in patients over time. Interestingly, those patients who did not return for follow-up showed reduced frontal MMN and fronto-central P3a amplitudes compared to their peers who did return for repeat assessment.

CONCLUSIONS

This study provides some evidence of the predictive utility of MMN at the early stages of schizophrenia- and affective-spectrum disorders and demonstrated that MMN impairments in such patients may worsen over time. Specifically, we found that young patients with the most impaired MMN amplitudes at baseline showed the most severe levels of disability at follow-up. Furthermore, in the subset of patients with repeat neurophysiological testing, central MMN was further impaired suggestive of neurodegenerative effects. MMN may serve as a neurophysiological biomarker to more accurately predict functional outcomes and prognosis, particularly at the early stages of illness.

Differential BOLD responses to auditory target stimuli associated with a skin conductance response

BACKGROUND

The orienting reflex (OR) is a fundamental biological mechanism thought to reflect automatic adaptive processing of environmental stimuli necessary for successful interaction with the environment. It has been hypothesized that the OR is generated in response to novelty such as in the case where a mismatch results between an internal neuronal template stored in working memory and incoming stimuli. Recent blood oxygenated level dependant (BOLD) activation studies that have investigated networks involved in the processing of novelty have suggested the recruitment of a distributed limbic-neocortical network. In the present study, event-related functional resonance imaging with simultaneous autonomic electrodermal activity was used to detect single trials of an auditory oddball task associated with the OR.

RESULTS

The pattern of activations indicated two distinct, but partially overlapping, networks. Predominantly, frontal activations were seen for the target stimuli that did elicit an OR, including the orbitofrontal gyrus and anterior cingulate gyrus, as well as activations in the anterior thalamus and cerebellum. On contrary, parietal activations including the supramarginal gyrus and precuneus were seen for the target stimuli that that did not elicit an OR.

The effects of fear on performance monitoring and attentional allocation

Evidence from event-related potential (ERP) studies indicates abnormal error processing and attentional allocation in "trait"-anxious individuals. However, few studies have been conducted that evaluate relevant ERP components during the induction of an anxious state (i.e., fear). In the present study, ERPs were measured in 16 undergraduates during control and fear induction conditions to examine the effects of fear on error processing and attentional allocation. Despite comparable performance in both experimental conditions, the ERP data indicated reductions in attentional allocation and error salience during fear induction. Fear did not appear to directly alter early error processing, as indicated by the error-related negativity, however. The implication of these results for understanding how trait and state anxiety may affect error processing and attentional allocation are discussed.

Distinct pattern of P3a event-related potential in borderline personality disorder

P3a and P3b event-related brain potentials to auditory stimuli were recorded for 17 unmedicated patients with borderline personality disorder, 17 matched healthy controls and 100 healthy control participants spanning five decades. Using high-resolution fragmentary decomposition for single-trial event-related potential analysis, distinctive disturbances in P3a in borderline personality disorder patients were found: abnormally enhanced amplitude, failure to habituate and a loss of temporal locking with P3b. Normative age dependencies from 100 controls suggest that natural age-related decline in P3a amplitude is reduced in borderline personality disorder patients and is likely to indicate failure of frontal maturation. On the basis of the theories of Hughlings Jackson, this conceptualization of borderline personality disorder is consistent with an aetiological model of borderline personality disorder.

Characterization of N200 and P300: selected studies of the Event-Related Potential

The Event-Related Potential (ERP) is a time-locked measure of electrical activity of the cerebral surface representing a distinct phase of cortical processing. Two components of the ERP which bear special importance to stimulus evaluation, selective attention, and conscious discrimination in humans are the P300 positivity and N200 negativity, appearing 300 ms and 200 ms post-stimulus, respectively. With the rapid proliferation of high-density EEG methods, and interdisciplinary interest in its application as a prognostic, diagnostic, and investigative tool, an understanding of the underpinnings of P300 and N200 physiology may support its application to both the basic neuroscience and clinical medical settings. The authors present a synthesis of current understanding of these two deflections in both normal and pathological states.

A Temporal Dissociation of Subliminal versus Supraliminal Fear Perception: An Event-related Potential Study

Current theories of emotion suggest that threat-related stimuli are first processed via an automatically engaged neural mechanism, which occurs outside conscious awareness. This mechanism operates in conjunction with a slower and more comprehensive process that allows a detailed evaluation of the potentially harmful stimulus (LeDoux, 1998). We drew on the Halgren and Marinkovic (1995) model to examine these processes using event-related potentials (ERPs) within a backward masking paradigm. Stimuli used were faces with fear and neutral (as baseline control) expressions, presented above (supraliminal) and below (subliminal) the threshold for conscious detection. ERP data revealed a double dissociation for the supraliminal versus subliminal perception of fear. In the subliminal condition, responses to the perception of fear stimuli were enhanced relative to neutral for the N2 “excitatory” component, which is thought to represent orienting and automatic aspects of face processing. By contrast, supraliminal perception of fear was associated with relatively enhanced responses for the late P3 “inhibitory” component, implicated in the integration of emotional processes. These findings provide evidence in support of Halgren and Marinkovic's temporal model of emotion processing, and indicate that the neural mechanisms for appraising signals of threat may be initiated, not only automatically, but also without the need for conscious detection of these signals.

P300 (Latency) Event-Related Potential: An Accurate Predictor of Memory Impairment

To determine if P300 latency changes precede and correlate with memory and mental status, patients (N=1506 aged 20–100 years) who received medical and psychiatric diagnoses (from 1997 to 2002), were assessed for P300 (N=1496), WMS-III (N=694), and MMSE (N=456). Patient and control groups included, a) normal WMS-III on all 4 subscales (N=36), b) normal WMS-III and MMSE (N=189) with subjective memory/mental status complaints, and c) medical patients with normal WMS-III and no memory complaints (N=205), and d) P300 control group without medical, psychiatric or memory problems for ROC.

Patients with impaired/borderline memory had a prolonged P300 latency (P<0.02) compared to age matched non-impaired controls; in patients with normal WMS-III/MMSE, with subjective mild memory/mental status impairment, P300 latency was prolonged compared to controls (P=0.0004). The P300 latency increased by 0.72ms per year (P=7.9×10−65) and voltage decreased by 0.03dV per year (P=6.7×10−10), and both parameters were linearly correlated with the age of the subjects.

Male subjects had an average voltage of 6.1dV and female 6.8dV(P=0.00009). Statistically, prolonged latency began at age range 41–50 (P=0.0002); reduced P300 voltage began at age range 51–60 (P=0.003). WMS-III memory decline for all measures began in females at age range 61–70 (P value at least=0.02) and for males at age range 61–80 (P=0.02). Prolonged P300 latency (P≤0.0001) and memory impairment (at least <0.02) were greater for females than males. MMSE memory decline, male and female, began at age range 81–90 (P value of at least 0.00007).

In our logistic regression model P300 latency was more predictive of WMS-III impairment than MMSE >24. In patients whose WMS-III score is impaired ≤69, or borderline ≤79 (P at least =0.004), a P300 latency more prolonged than the norm (≥300 + 30 + Age) identifies these patients, whereas a MMSE >24 failed. With the ROC curve, we confirmed that P300 latency could accurately identify borderline/impaired memory.

ERPs associated with and without an "orienting reflex" in patients with schizophrenia

In this study, we measured traditional late components of the Event Related Potential (ERP: N 100, P 200, N 200 and P 300) in a conventional auditory oddball paradigm, but additionally and simultaneously assessed electrodermal "orienting reflexes (ORs)" in 40 patients with schizophrenia and 40 age and gender matched normal controls. The single epoch ERPs that did and did not evoke an OR, were sub-averaged separately. The control subjects (but not the patient group), revealed delayed P 300 latency in the ERP sub-averages without ORs (ERP-OR), compared with ERP sub-averages with ORs (ERP+OR). Between-group analysis showed reduced N 100, N 200 and P 300 amplitudes (as well as delayed P 300 latency) in the ERP+OR sub-average in patients with schizophrenia. In the ERP-OR sub-average, the patient group also had smaller N 100, N 200 and P 300 amplitudes, but larger P 200 amplitude (compared with normal controls). This study shows the potential to tease out physiologically based OR sub-processes, by simultaneous acquisition and analysis of ERPs and autonomic electrodermal activity. Such ERP sub-averages (based on autonomic responses) highlight that multiple processes overlap across the trial, and their delineation may elucidate more specific patterns of disturbance in schizophrenia, than traditional averaged measures.

On the relationship of P3a and the Novelty-P3

Deviant stimuli give rise to a late positive ERP component with latencies from 250 to 400 ms. Target deviants elicit a P300 with maximum amplitude over parieto-central recording sites while the 'P300' elicited by deviant nontarget stimuli occurs somewhat earlier and shows a more frontally-oriented scalp distribution. Two varieties of frontal P300s have been described, elicited either by rare stimuli (target or nontarget) presented in a two-stimulus oddball task (P3a) or by infrequent, unrecognizable stimuli presented in the context of a three-stimulus oddball task (Novelty-P3). The Novelty-P3 has been observed in a number of subsequent studies; the P3a has not been extensively studied and both its significance and existence have been called into question. The present report describes a replication of two prototypical studies with 'frontal' P3s observed in each context. Application of factor analysis to the two sets of ERP waveforms does not support a distinction between these two components.

Perseveration for novel stimuli in Parkinson's disease: an evaluation based on event-related potentials topography

Event-related potential topography produced by novel and target stimuli was used to detect dysfunction of mental switching (perseveration) in nondemented patients with Parkinson's disease. The study participants were 15 patients with Parkinson's disease and 13 age-matched healthy control patients. Ten percent of the novelty tones with pitches of 125 and 500 Hz were added to 20% of the target tones that had a pitch of 1000 Hz. Patients were instructed to count the target tones. The modified Wisconsin Card Sorting Test was used to evaluate frontal lobe function. Patients with Parkinson's disease showed a significant decrease in the achieved categories and an increase in perseverative errors in the Wisconsin Card Sorting Test. These results indicate that the cognitive impairment of patients with Parkinson's disease can be characterized as failure of mental switching related to frontal lobe dysfunction based on basal ganglia disturbance. As compared with the control patients, patients with Parkinson's disease had shorter P3 latencies to the novel stimuli and a more frontal distribution on the P3 map, especially for the 125-Hz stimuli. This characteristic of P3 to novel stimuli in the patients with Parkinson's disease, but not in the control patients, is categorized by P3a (novelty P3). Our findings suggest that decreased mental switching causes lack of novelty P3 habituation in patients with Parkinson's disease and that it is related to learning disabilities based on dysfunction of the frontal lobe and basal ganglia.

Impaired novelty detection and frontal lobe dysfunction in Parkinson's disease

Recent evidence suggests that the frontal lobe plays an important role in an orienting response to novel events, and that frontal lobe dysfunction is linked to attentional and cognitive deficits in Parkinson's disease (PD). We tested the hypothesis that the neural network involved in novelty detection may be impaired in PD patients by studying event-related brain potentials to target and novel stimuli and their correlation to performance in neuropsychological tests in non-demented PD patients. The PD patients showed prolonged P3 latency to novel stimuli compared with age-matched controls, whereas their P3 latency to target stimuli was not different from that in controls. The PD patients also manifested amplitude reduction and less habituation of the P3 to novel stimuli over frontal scalp sites compared with controls. The prolonged latency and frontal reduction of novelty P3 correlated with a poor performance in the Wisconsin Card Sorting Test. These results suggest that the orienting response of PD patients to novel events is impaired and that recording novelty P3 might provide a neurophysiological and quantitative measure of attentional and cognitive deficits linked to the frontal lobe in non-demented PD patients.

Habituation of event-related potentials in patients with Parkinson's disease

Auditory event-related potential (ERP) was studied in idiopathic Parkinson's disease (PD) using our new procedures. We examined 12 non-demented patients with PD, and 9 age-matched control subjects. Ninety responses induced by rare stimulation were continuously recorded from Fz, Cz, Pz referred to linked earlobe electrode (A1A2), and were divided into nine blocks (one block = 10 responses) for statistical analysis. We assessed the habituation of auditory ERP to detect delicate changes related to the information processing in PD. N100 and P300 latencies were significantly longer in PD than in control subjects (p<0.05). P300 latency gradually increased with progression of recording blocks in both PD and control subjects, whereas N100 latency increased only in PD. Three way analysis of variance for P300 amplitude revealed significant effects of subject group, recording electrode site, and trial block. P300 amplitude was smaller in PD than in control subjects. Significant negative correlation between P300 amplitudes and block numbers were observed at Cz and Pz in PD, and at Fz in the control group. Previous reports as well as present results suggest that prolongation of N100 latency might be related to frontal lobe dysfunction, and abnormality of P300 to dysfunction in both the frontal lobe and hippocampus in PD.

Effect of interstimulus interval on visual P300 in Parkinson's disease

OBJECTIVE

Visual event related potentials (ERPs) were studied during an oddball paradigm, to testify whether cognitive slowing in Parkinson's disease exists and to investigate whether cognitive information processing can be influenced by different interstimulus intervals (ISIs) of an oddball task in patients with Parkinson's disease and normal subjects.

METHODS

ERPs and reaction time were measured in 38 non-demented patients with Parkinson's disease and 24 healthy elderly subjects. A visual oddball paradigm was employed to evoke ERPs, at three different interstimulus (ISI) intervals: ISI(S), 1600 ms; ISI(M), 3100 ms; and ISI(L), 5100 ms. The effect of ISIs on ERPs and reaction time was investigated.

RESULTS

Compared with the normal subjects, P300 latency at Cz and Pz was significantly delayed after rare target stimuli in patients with Parkinson's disease only at ISI(L). Reaction time was prolonged in patients at all the three ISIs, compared with the normal controls. There was also significantly delayed N200 and reduced P300 amplitude at Cz and/or Pz to rare non-target stimuli in patients at the three ISIs, compared with the normal controls. During rare target visual stimulation, P300 latency and reaction time in the patients with Parkinson's disease and reaction time in the normal subjects were gradually prolonged as the ISI increased.

CONCLUSION

Prolonged N200 latency to rare non-target stimuli might indicate that automatic cognitive processing was slowed in Parkinson's disease. Cognitive processing reflected by P300 latency to rare target stimuli was influenced by longer ISI in patients with Parkinson's disease.

Brain imaging technologies: how, what, when and why?

OBJECTIVE

Innovations in physics and computing technology over the past two decades have provided a powerful means of exploring the overall structure and function of the brain using a range of computerised brain imaging technologies (BITs). These technologies offer the means to elucidate the patterns of pathophysiology underlying mental illness. The aim of this paper is to explore the current status and some of the future directions in the application of BITs to psychiatry.

METHOD

Brain imaging technologies provide unambiguous measures of brain structure (computerised tomography and magnetic resonance imaging [MRI]) and also index complementary measures of when (electroencephalography, event related potentials, magnetoencephalography) and where (functional MRI, single photon emission computed tomography, positron emission tomography) aspects of brain activity occur.

RESULTS

The structural technologies are primarily used to exclude a biological cause in cases of a suspected psychiatric disorder. The functional technologies show considerable potential to delineate subgroups of patients (that may have different treatment outcomes), and evaluate objectively the effects of treatment on the brain as a system. What is seldom emphasised in the literature are the numerous inconsistencies, the lack of specificity of findings and the simplistic interpretation of much of the data.

CONCLUSION

Brain imaging technologies show considerable utility, but we are barely scratching the surface of this potential. Simplistic over-interpretation of results can be minimised by: replication of BIT findings, judicious combination of complementary methodologies, use of appropriate activation tasks, analysis with respect to large normative databases, control for performance, examining the data'beyond averaging', delineating clinical subtypes, exploring the severity of symptoms, specificity of findings and effects of treatment in the same patients. The technological innovation of BITs still far outstrips the sophistication of their use; it is essential that the meaning and mechanisms underlying BIT measures are always evaluated with respect to prevailing models of brain function across disciplines.