Akinori Hozumi

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 Parkinsons disease. The study participants were 15 patients with Parkinsons 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 Parkinsons 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 Parkinsons 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 Parkinsons 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 Parkinsons 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 Parkinsons disease and that it is related to learning disabilities based on dysfunction of the frontal lobe and basal ganglia.

Insufficient Processing Resources in Parkinson's Disease: Evaluation Using Multimodal Event-Related Potentials Paradigm

The purpose of our study was to demonstrate impaired allocation of processing resources in non-demented patients with early-stage mild Parkinsons disease (PD) using a multimodal event-related potential (ERP) paradigm. The multimodal ERP paradigm was performed in 18 non-demented medicated patients with early-stage PD (Mini-Mental State Examination Score >26) and 16 matched normal controls, the Global Field Power (GFP) was employed for ERP components analysis, and the new modified Wisconsin Card Sorting Test (WCST) was used to evaluate frontal lobe function. Patients with PD did not exhibit novelty P3s, and P3 latency to non-target novel stimuli in visual and auditory modalities was significantly longer in PD patients than in controls. P3 amplitude for the target stimuli (P3b) was higher in PD in both auditory and visual modalities; however, P3b latency was not different between the two groups. Patients with PD showed a significantly lower score of achieved categories and made more perseverative errors in WCST as compared to controls. Our results showed that there were no natural novelty P3s in patients with PD; this finding suggests that non-demented patients with mild PD do not have sufficient mental resources to allocate to the central executive, due to dysfunction of the frontal lobe.

Facial diplegia with paraesthesias: facial nerve enhancement in three dimensional MRI

Facial diplegia (bilateral facial paralysis) is a rare clinical finding that can be the presenting symptom in a wide range of diseases.1 It occurs in about 50% of patients with Guillain-Barre syndrome (GBS). Guillain-Barre syndrome causes regional and functional variants with unusual features. Ropper described four patients with facial diplegia and distal limb paraesthesias, and he defined them as having a rare variant form of GBS because of shared clinical, electrophysiological, and CSF features.2 The aetiology and nosological position of facial diplegia presenting in this variant form is still controversial. We experienced a patient who had bilateral facial paralysis, distal limb paraesthesias, and diminished reflexes whose contrast enhanced three dimensional MRI (3-D MRI) showed enhancing lesions in the bilateral facial nerves. A 27 year old woman had nasal discharge and coughing. One week later she noticed paraesthesias in her fingers and toes. Nine days after the …

Abnormal information processing in dementia of Alzheimer type. A study using the event-related potential's field.

Abstract Electrical field changes of event-related potentials (ERPs) were investigated in 26 patients with dementia of Alzheimers type (DAT) and 12 age-matched normal subjects. The patients were assessed with the Clinical Dementia Rating and Mini-Mental State. Each patient selected had only mild to moderate mental disability. Auditory oddball stimulation was presented at 1.5 s intervals and 1000 Hz for the nontarget and 2000 Hz for the target tones, both at 85 dB. The target tones were 20% of all the tones. The reference-independent data (latency, global field power: GFP, dissimilarity index: DISS and location of centroids) were obtained and analyzed for each ERP component. The momentary electric strength or ‘hilliness’ of the ERPs landscape was indicated by GFP. The patients showed prolonged latencies and decreased P300 GFP amplitudes and of N100 GFP. These findings suggest that the abnormal electrical field of ERP may reflect abnormal information processing following the attentional process for target stimuli in DAT patients.

Chapter 7 The role of the basal ganglia and cerebellum in cognitive impairment: a study using event-related potentials

Publisher Summary This chapter determines the profile and difference of cognitive impairment in disturbance of the basal ganglia and cerebellum using event-related potentials (ERPs) and a battery of neuropsychological tests. The results show a disturbance of inhibitory function in patients with Parkinsons disease (PD) during the non-target stimuli (NoGo) condition when performing the continuous performance task (CPT) paradigm. Inhibition is an important contributory process in successful selective attention, and selective attention has been shown to be disrupted by frontal lobe dysfunction. Both human and animal studies have demonstrated that the prefrontal damage disrupts inhibitory modulation. The prefrontal lobe has a critical role in the process of inhibitory control.

Higher brain function disturbance in Parkinson's disease patients: an evaluation based on electrophysiological investigation

Abstract Background : Higher brain function disturbance such as the central executive of working memory impairment is thought to exist even in early-stage nondemented idiopathic Parkinsons disease patients (PDPs). Methods : Resting EEG, simple oddball paradigm and novel task event-related potentials (ERPs) topography were measured in early-stage nondemented PDPs (MMSE>26), and age-matched normal controls (NCs). The new modified Wisconsin Card Sorting Test (WSCT) was used to evaluate the frontal lobe function. Results and interpretation : There were no natural novelty P3s to be found in PDPs. P3b latency did not differ between PDPs and controls. In addition, increased P3b amplitude for the target stimulus was found in nondemented PDPs. Moreover, the nondemented PDPs showed increased amplitude of resting EEG. PDPs showed significant decreasing of the achieved categories and increasing of perseverative errors in WSCT. Conclusions : The results of the present study suggest that higher brain function disturbance such as the central executive of working memory impairment in nondemented PDPs may be based on the disturbance of mental set change, parallel processing and inhibition of the cortical function due to dysfunction of basal ganglia.

The efficacy of the levodopa on cognitive function in patients with de novo Parkinson's disease

Abstract We investigated the efficacy of the levodopa on cognitive function in patients with de novo Parkinsons disease (PD) using the event-related potential (ERP) measure and neuropsychological test batteries. We studied 12 PD patients who had never received anti-Parkinson medications. The ERP with auditory oddball P3 paradigm and neuropsychological tests such as Mini-Mental State Examination (MMSE), New Modified Wisconsin Card Sorting Test (WCST) and Trail Making test were repeated in the patients before and after administration of levodopa plus benserazide daily 300 mg. For the ERPs components, reference-independent measures (global field power, GFP) were determined, and P3 GFP peak, peak latency and topography were assessed. After administration of levodopa, the patients revealed significant increase of the achieved categories and decrease of perseveration errors in the WSCT, shortening of time in Trail Making test, although MMSE score showed no significant difference. The P3 GFP peak attenuated, although there were no differences in peak latency or on scalp topography. These findings suggest that levodopa affect to the neural circuit connect frontal cortex with the striatum and normalize its function, and it causes decrease of P3 GFP peak reflecting appropriate resource allocation.

Efficacy of the Levodopa on Frontal Lobe Dysfunction in Patients with de Novo Parkinson’s Disease; A Study Using the Event-related Potential

We investigated the efficacy of the levodopa on cognitive function in patients with de novo Parkinson’s disease (PD) using the event related potential (ERP) measure and neuropsychological test batteries. We studied 20 PD patients who had never received anti Parkinson medications. After administration of levodopa, the patients revealed significant increase of the achieved categories and decrease of preservation errors in the WSCT, shortening of time in Trail Making Test although MMSE score showed no significant difference. The P3 peak attenuated although there were no differences in peak latency or on scalp topography. These findings suggest that levodopa affect to the neural circuit connect frontal cortex with the striatum and normalize its function, and it causes decrease of P3 peak reflecting appropriate resource allocation. In addition, P3 might be more appropriate indicator rather than psychological test

EEG evaluation of spinocerebellar degeneration with low resolution brain electromagnetic tomography

Abstract This study is aimed to search for the brain electric signature under the resting condition of spinocerebellar degeneration (SCD) patients and to assess the relation between cerebellum and cognitive function without the motor factor. We studied 12 SCD patients and 12 aged normal sex matched controls (NC). We recorded spontaneous eyes-closed resting EEGs to 20 locations of the international 10/20 system. Twenty artifact-free EEG epochs, consisting of 2 s were selected for each subject and filtered into seven frequency bands. The gravity center was calculated and the mean vector was compared between the two groups using unpaired t -tests. Low Resolution Electromagnetic Tomography (LORETA) was used to compute the three-dimensional intracerebral distribution of electric activity for each EEG band. The images of two groups were then statistically compared using nonparametric randomization tests, with correction for multiple testing. The vector analysis between SCD and NC revealed significant differences in alpha2 and beta2. In the LORETA analysis, SCD showed stronger activation in the delta band in the cingulate gyrus and decreased activation in the alpha1 band in the superior frontal gyrus. The present results suggested that the frontal and limbic lobes are inhibited in SCD patients under resting condition. The findings supported that the cerebellum was involved in cognitive function regardless of motor adjunct.

Evaluation of cognitive function in spinocerebellar ataxia—a study using event-related potential

Abstract The purpose of this study is to determine the profile of cognitive impairment of spinocerebellar ataxia, especially the cortical cerebellar atrophy (CCA), using event-related potential (ERP) measures and neuropsychological test batteries. We studied 13 CCA patients and 13 age- and sex-matched controls. For ERP recording, we submitted not only conventional auditory oddball task but also the continuous performance test (CPT), which investigates the attentional performance and the ability to control a motor response, i.e. to execute (Go) or inhibit a motor reaction (NoGo). Brain electric data was obtained from 20 channels and recomputed into a series of potential distribution maps using Biologic Brain Atlas. For the ERPs components, reference-independent measures (global field power=GFP; Lehmann D. and Skrandies W 1980) were determined. Furthermore, low resolution electromagnetic tomography (LORETA) was used to compute the three-dimensional intracerebral distribution of electric activity of Go/NoGo P3 components. The Mini-Mental State Examination (MMSE), the Japanese version of Wechsler Adult Intelligence Scale-Revised (WAIS-R) and the New Modified Wisconsin card sorting test (WCST) were also assessed. The CCA patients showed prolonged GFP peak latency and attenuated GFP peak in NoGo condition, although there were no differences in auditory oddball task and in Go condition. LORETA indicated that CCA patients showed decreased activation of frontal source in NoGo P3 of NC. However, the patients revealed no significant differences both in the WSCT and in the MMSE compared with NC. These findings suggest that degeneration of cerebellum contribute greatly to the frontal dysfunction. And this dysfunction is characterized by the impairment of inhibitory system.