Mio Arai

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.

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

Evaluation of transcranial magnetic stimulation for depressed Parkinson's disease with LORETA

Abstract To evaluate the efficacy of low-frequency repetitive transcranial magnetic stimulation (rTMS) for depressed Parkinsons disease (PD) patients, we examined a series of clinical test batteries and analyzed the EEG data with Low Resolution Electromagnetic Tomography (LORETA). We studied seven depressed PD patients. The severity of all PD patients assessed by the Hoehn and Yahr stage was higher than stage 2. The patients underwent 0.2 Hz rTMS to the frontal areas using a large circular coil for 20 times per day at an intensity of 1.5 T. Sessions were performed for 5 successive days. The motor activity with finger tapping and 20-m walking, Unified Parkinsons Disease Rating Scale, and actigraphy were used to assess changes in the clinical performance before and after rTMS. Furthermore, we recorded 20-channel spontaneous eyes-closed resting EEGs. Each 2-s artifact-free epoch was digitally filtered into seven frequency bands. LORETA was used to compute the three-dimensional intracerebral distribution of electric activity of each of the EEG frequency bands. Images of before and after rTMS were statistically compared using non-parametric randomization tests with corrections for multiple testing. The subjects showed improvements of motor activity and relief of depression after TMS. LORETA showed stronger activation in the theta band in the right superior temporal gyrus, and decreased activation in the alpha1 and beta1 bands in the frontal gyrus. These results suggest that low-frequency rTMS may be a valuable technique in the adjunct treatment of depressed PD patients, possibly by inducing changes of the cortical inhibitory system.

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.

The efficacy of fluvoxamine for poststroke depression—an evaluation using event-related potentials topography

Abstract Poststroke depression (PSD) is known as depression after a stroke, while the depression due to silent cerebral infarction (SCI) is called MRI, defined as vascular depression (VaD). On the other hand, selective serotonin re-uptake inhibitor (SSRI) may be well tolerated and effective for the treatment of PSD and VaD. However, there is no pathophysiological study of SSRI for PSD and VaD. Event-related potentials (ERPs), especially P3 (P300), is considered an electrophysiological parameter of the cognitive processes of attention, memorization and discrimination of stimuli. To pathophysiologically determine the efficacy of fluvoxamine in a PSD patient, we submitted ERPs and made evaluations. After the administration of fluvoxamine, P3 latency decreased and its amplitude increased in the oddball and continuous performance task paradigm. In addition, the amplitude of novel P3 increased in the novel paradigm. These ERP data suggest that the improvement of the depressive state by fluvoxamine administration in this patient is based on the amelioration of the cognitive function, especially with the failure of working memory due to the frontal lobe dysfunction. Our study clarified that the cognitive dysfunction, such as mental set and working memory disturbance, existed for the part in PSD patients and its dysfunction improved with the administration of fluvoxamine.