Toshiaki Kamitani

Visual event-related potentials in progressive supranuclear palsy, corticobasal degeneration, striatonigral degeneration, and Parkinson's disease

Abstract To determine whether there are characteristic changes in event-related potentials (ERPs) in parkinsonian syndromes we studied 8 patients with progressive supranuclear palsy (PSP), 10 patients with corticobasal degeneration (CBD), 9 patients with striatonigral degeneration (SND), and 16 patients with idiopathic Parkinsons disease (PD) with a mean duration of illness shorter than 5 years in each group. A visual oddball paradigm was employed to elicit P300. P300 to the rare target and rare nontarget stimuli and reaction time (RT) to rare target stimuli in each group were compared with those in the corresponding age-matched normal control group and to each other after age correction. The correlation of P300 and RT to motor disability score was also studied. In PSP P300 amplitude was markedly reduced while in CBD P300 latency was prolonged. P300 amplitude to rare nontargets in SND and PD was attenuated. The mean RT in the PSP and the CBD group was significantly longer than in the other two groups. The mean RT in PD and P300 amplitude to rare nontargets in both CBD and PD showed significant correlation with the severity of motor disability. Simultaneous measurement of P300 and RT may yield useful supplementary information in facilitating diagnosis of parkinsonian syndromes in addition to clinical criteria.

Do P1 and N1 evoked by the ERP task reflect primary visual processing in Parkinson's disease?

Objectives: To evaluate whether P1 and N1 evoked by ERP tasks could appropriately reflect primary visual processing in Parkinsons disease (PD). Methods: We recorded ERPs in 13 PD patients with duration of illness less than 5 years and 18 age-matched normal control subjects. P1 and N1 from Oz were evoked by a visual oddball and a delayed matching S1-S2 task. The effect of different events on P1 and N1 was studied. All patients were given an ECD-SPECT examination, and the SPECT images were overlaid on the 3D-MRI. The correlation of P1 or N1 to the regional cerebral blood flow (rCBF) was studied. Results: P1 was not influenced by different events. There was no significant P1 differences between the PD and the normal group. N1 was significantly shorter and smaller in the patients than that in the normal group. N1 amplitude after the waveform subtraction (target-frequent) in the PD group did not show significant difference with that in the normal controls, nor with the N1 before the subtraction. Nd, the subcomponent of N1 after the subtraction in the patients was significantly earlier and smaller than that in the normal controls. P1 only weakly correlated with the rCBF in the occipital lobe. N1 was correlated with the rCBF in a global region. Conclusions: The results provided some evidence that P1 might reflect the primary visual processing, and N1 might be involved in both primary and cognitive visual processing. The altered N1 in the PD patients might be due to the deformed Nd.

The correlation between P300 alterations and regional cerebral blood flow in non-demented Parkinson's disease.

P300 was evoked by a visual oddball and an S1-S2 task in 22 non-demented Parkinsons disease (PD) patients (13 in the early stage, nine in the late stage) and 18 normal controls. Reaction time was also measured. All patients undertook the (99)Tc-ECD SPECT examination. Quantitative regional cerebral blood flow (rCBF) was obtained by overlying SPECT image on the 3D-magnetic resonance image. In the PD patients in the late stage, P300 latency to S2-same and reaction time were significantly prolonged, while rCBF at bilateral frontal, temporal, and the right parietal lobes was decreased. P300 latency to S2-same was significantly correlated with the rCBF at bilateral temporal lobes. Reaction time was significantly correlated with the rCBF at the right frontal and parietal lobes, as well as the temporal and occipital lobes. The results suggest that P300 changes in non-demented PD in the late stage could be related to the temporal lobe dysfunction.

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.

Visual event-related potential changes at two different tasks in nondemented Parkinson's disease

A visual oddball paradigm and an S1-S2 paradigm were employed to evoke event-related potentials (ERPs) in 38 nondemented Parkinsons disease (PD) patients and 24 healthy elderly subjects. Delayed N200 and reduced P300 amplitude in the whole PD sample were only found in the S1-S2 paradigm. Delayed N200 and reaction time in PD with short duration of illness were found only after the S1-S2 paradigm, which might be an early sign of cognitive changes in PD. This is the first study to apply an S1-S2 paradigm for a visual P300 test in PD and proved the value of this paradigm for detecting minor cognitive abnormalities. ERP changes were correlated with clinical features. Reduced P300 amplitude for the S1-S2 paradigm was significantly correlated with WAIS-R scores and gait disturbance. The correlation between P300 amplitude and clinical scores has rarely been discussed before. P300 latency during the oddball paradigm in PD was influenced by age at test, age at onset, and duration of illness. This may explain why P300 results in nondemented PD have varied among previous authors.

Early sensory information processes are enhanced on visual oddball and S1–S2 tasks in Parkinson's disease: a visual event-related potentials study

To observe sensory and cognitive information processing in Parkinsons disease (PD), 34 PD patients and 26 controls were investigated. A visual oddball paradigm and an S1-S2 paradigm were employed to record the early (P1, N1, P2) and late (N2, P3) event-related potentials (ERPs) at Cz, Pz and Oz. Results showed: (1) enlarged P1 amplitude at all electrode locations on both tasks, (2) shortened N1 latency and enlarged P2 amplitude at Oz on both tasks, (3) enlarged N1 amplitude at Cz during an oddball paradigm, (4) delayed N2 latency and decreased N2, P3 amplitude on both tasks, and (5) delayed P3 latency and reaction time during the S1-S2 paradigm. Abnormal ERP changes were correlated with worsened scores on Wechsler Adult Intelligence Scale-Revised and motor dysfunction scales in PD. We surmise overactive aspects or failed inhibitory modulation of sensory information processing in the early ERP stage and deficient cognitive information processing during the late ERP stage in PD.

Visual evoked potential changes related to illusory perception in normal human subjects

To study the human brain activity correlated with illusory perception, we chose a physically flat plane figure which looks like a convex figure. We studied visual evoked potential (VEP) changes, which reflect perceptual properties of illusory perception. We defined two paradigms, an illusory paradigm (IP) and a control paradigm (CP). Two stimuli, A and B, were randomly presented in the IP, while stimuli C and D were randomly presented in the CP. Stimulus A was the only figure which looked like a convex figure. A three-way analysis of variance was applied to the VEP components in each paradigm, with three factors: figures, electrodes, and sessions. Different configuration patterns between the two paradigms explained different grand mean VEP waveforms between the two paradigms; a greater N1 for the CP, a greater P1 for the IP, and marked attenuation of the N3 and P3 components for the IP. Significant main effects of figures only for the IP were found on P1 and P1N2 amplitude and P2 latency, which are assumed to reflect perceptual properties of stereoscopical illusory perception.

Visual event-related potential changes in two subtypes of multiple system atrophy, MSA-C and MSA-P

Abstract We investigated the visual event-related potentials (ERPs) in two subtypes of multisystem atrophy (MSA) in 15 MSA-C patients, 12 MSA-P patients, and 21 normal control (NC) subjects. We used a visual oddball task to elicit ERPs. No significant changes were seen in N1 or N2 latency, in either MSA-C or MSA-P, compared with the NC group. An early stage of visual information process related to N1 and a visual discrimination process related to N2 might be preserved in both MSA-C and MSA-P. The P3a peak was more frequently undetectable in MSA than in the NC group. Significant P3a amplitude reduction in both MSA-C and MSA-P suggests impairment of the automatic cognitive processing in both MSA-C and MSA-P. Significant difference was found in P3b latency and P3b amplitude only in MSA-C, compared with the NC group. The result suggests the impairment of the controlled cognitive processing after the visual discrimination process in the MSA-C group. We further investigated the correlation between visual ERP changes and magnetic resonance imaging (MRI) data. Quantitative MRI measurements showed reduced size of the pons, cerebellum, perisylvian cerebral area, and deep cerebral gray matter in both MSA-C and MSA-P, and of the corpus callosum only in MSA-P, as compared to NC group. In both MSA-C and MSA-P, P3b latency was significantly correlated with the size on MRI of the pons and the cerebellum. P3b latency in the whole MSA group was also significantly correlated with the size of the pons and the cerebellum. These results indicate that P3b latency changes in parallel with the volume of the pons and the cerebellum in both MSA-C and MSA-P.

Relationship between cerebellar size and variation of reaction time during a visual cognitive task in normal subjects

Sirs: In a previous study recently reported in this journal [5], we compared event-related potentials (ERPs) during a visual oddball task between 27 multiple system atrophy (MSA) patients and 21 normal control subjects.We also investigated the relationship between morphological changes in the brain and visual ERP changes in the MSA patients.After this study was finished, we further analysed the relationship between brain MRI data and ERP measurements during a visual oddball task in the normal control subjects.We found that midline and lateral cerebellar sizes were inversely correlated with the standard deviation (SD) of the reaction time in normal elderly subjects. Twenty-seven normal human subjects (10 men, 17 women) participated in our study. The age of the subjects in years ranged from 42 to 80, with a mean of 63±11. All the subjects were healthy, righthanded subjects without any history of neurological, psychiatric, or ophthalmological diseases. All 27 subjects were asked to perform a choice reaction task (an oddball task). Six of the subjects were also asked to perform a simple reaction task. The choice reaction task was the same task as that used in a previous study [5]. During the task, three kinds of visual stimuli were randomly presented: rare target (20 %), rare nontarget (20 %), and frequent nontarget (60 %). The choice reaction time was measured after the subjects were instructed to press the button only for rare targets with the right thumb as rapidly and correctly as possible. During the test session, a total of 100 visual stimuli included 20 rare targets. On 20 choice reaction time measurements for 20 rare targets in each individual subject, we calculated the mean, the standard deviation (SD) and the coefficient of variation (CV [%] = SD/ mean 100). During the simple reaction task, we employed the same visual stimuli as used in the choice reaction task (an oddball task), and instructed the six subjects to press the button for all visual stimuli with the right thumb as rapidly as possible. For 20 simple reaction time measurements for 4 rare targets, 4 rare nontargets, and 12 frequent nontargets in each individual subject, we calculated the mean, SD and CV. MRI was done with a 1.5-T MR imaging scanner (Signa, General Electric, Milwaukee, WI, USA) for all the twenty-seven subjects. Sagittal T1-weighted images were used for evaluation (echo time, 15 ms; repetition time, 500 ms). We examined three slices of the sagittal image with section thickness of 5 mm. The slices consisted of a midsagittal slice and two other slices which were located 12 mm lateral to the midsagittal slice (Fig. 1A). We measured the area of cerebellar slice excluding the cerebrospinal fluid (CSF) space, for the vermis (area B in Fig. 1B) and the left or right cerebellar hemisphere (area C in Fig. 1C). The intracranial area was defined as the region which contained the brain tissue and CSF space in the midsagittal slice (area D in Fig. 1D). We also measured the region which contained the cerebellar brain tissue and CSF space, for the vermis (area E in Fig. 1E) and the left or right cerebellar hemisphere (area F in Fig. 1F). These areas were measured using the procedure described in our previous report [5]. NIH Image version 1.62 was used for these MRI measuring procedures. The MRI ratio of the cerebellum was calculated, in order to compensate for individual variation in head size. The MRI ratio of the cerebellum (%) was defined as the cerebellar area/the intracranial area 100, for the vermis (area B/area D 100) and the left or right cerebellar hemisphere (area C/area D 100). We also calculated the atrophy index of the cerebellum, in order to evaluate dilatation of the cerebellar folia and fissure. Atrophy index of the cerebellum (%) was defined as [area E – area B]/area E 100 for the vermis, and as [area F – area C]/area F 100 for the left or right cerebellar hemisphere. We also examined an axial slice of the left and right cerebral hemispheres with section thickness of 10 mm, at a level of the basal ganglia, being parallel to the anterior commissure-posterior commissure line. The MRI ratio for each cerebral hemisphere was defined as the ratios of the brain parenchyma to the total cranial fossa which was measured as the region of both brain tissue and CSF space. Statistical analysis was performed using a Stat View J-5.0 computer program (SAS Institute Inc.). Student’s t test (paired) was employed for comparison between simple and choice reaction time measurements. Pearson’s correlation coefficients (r) were computed to study the correlations between choice reaction time measurements and MRI measurements. LETTER TO THE EDITORS

Visual event-related potential changes in multiple system atrophy: delayed N2 latency in selective attention to a color task.

Recent studies demonstrated an altered P3 component and prolonged reaction time during the visual discrimination tasks in multiple system atrophy (MSA). In MSA, however, little is known about the N2 component which is known to be closely related to the visual discrimination process. We therefore compared the N2 component as well as the N1 and P3 components in 17 MSA patients with these components in 10 normal controls, by using a visual selective attention task to color or to shape. While the P3 in MSA was significantly delayed in selective attention to shape, the N2 in MSA was significantly delayed in selective attention to color. N1 was normally preserved both in attention to color and in attention to shape. Our electrophysiological results indicate that the color discrimination process during selective attention is impaired in MSA.